Merge pull request #5348 from nicolasnoble/backport-merge

Backport merge.

127 files changed, 3086 insertions, 536 deletions

diff --git a/src/boringssl/gen_build_yaml.py b/src/boringssl/gen_build_yaml.py
index 7c7a57993f..3a7116b181 100755
--- a/src/boringssl/gen_build_yaml.py
+++ b/src/boringssl/gen_build_yaml.py
@@ -33,6 +33,8 @@ import sys
 import os
 import yaml
 
+sys.dont_write_bytecode = True
+
 boring_ssl_root = os.path.abspath(os.path.join(
     os.path.dirname(sys.argv[0]), 
     '../../third_party/boringssl'))
diff --git a/src/compiler/cpp_generator.cc b/src/compiler/cpp_generator.cc
index d3d6224de2..97295bed45 100644
--- a/src/compiler/cpp_generator.cc
+++ b/src/compiler/cpp_generator.cc
@@ -1106,6 +1106,7 @@ void PrintSourceService(grpc::protobuf::io::Printer *printer,
 
   printer->Print(*vars, "$ns$$Service$::Service::Service() {\n");
   printer->Indent();
+  printer->Print(*vars, "(void)$prefix$$Service$_method_names;\n");
   for (int i = 0; i < service->method_count(); ++i) {
     const grpc::protobuf::MethodDescriptor *method = service->method(i);
     (*vars)["Idx"] = as_string(i);
diff --git a/src/core/census/grpc_filter.c b/src/core/census/grpc_filter.c
index a8db32b9d5..c8aaf31e2d 100644
--- a/src/core/census/grpc_filter.c
+++ b/src/core/census/grpc_filter.c
@@ -107,8 +107,8 @@ static void server_mutate_op(grpc_call_element *elem,
   if (op->recv_initial_metadata) {
     /* substitute our callback for the op callback */
     calld->recv_initial_metadata = op->recv_initial_metadata;
-    calld->on_done_recv = op->on_complete;
-    op->on_complete = &calld->finish_recv;
+    calld->on_done_recv = op->recv_initial_metadata_ready;
+    op->recv_initial_metadata_ready = &calld->finish_recv;
   }
 }
 
diff --git a/src/core/census/mlog.c b/src/core/census/mlog.c
new file mode 100644
index 0000000000..a2cc46d3f2
--- /dev/null
+++ b/src/core/census/mlog.c
@@ -0,0 +1,600 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+// Implements an efficient in-memory log, optimized for multiple writers and
+// a single reader. Available log space is divided up in blocks of
+// CENSUS_LOG_2_MAX_RECORD_SIZE bytes. A block can be in one of the following
+// three data structures:
+// - Free blocks (free_block_list)
+// - Blocks with unread data (dirty_block_list)
+// - Blocks currently attached to cores (core_local_blocks[])
+//
+// census_log_start_write() moves a block from core_local_blocks[] to the end of
+// dirty_block_list when block:
+// - is out-of-space OR
+// - has an incomplete record (an incomplete record occurs when a thread calls
+//   census_log_start_write() and is context-switched before calling
+//   census_log_end_write()
+// So, blocks in dirty_block_list are ordered, from oldest to newest, by the
+// time when block is detached from the core.
+//
+// census_log_read_next() first iterates over dirty_block_list and then
+// core_local_blocks[]. It moves completely read blocks from dirty_block_list
+// to free_block_list. Blocks in core_local_blocks[] are not freed, even when
+// completely read.
+//
+// If the log is configured to discard old records and free_block_list is empty,
+// census_log_start_write() iterates over dirty_block_list to allocate a
+// new block. It moves the oldest available block (no pending read/write) to
+// core_local_blocks[].
+//
+// core_local_block_struct is used to implement a map from core id to the block
+// associated with that core. This mapping is advisory. It is possible that the
+// block returned by this mapping is no longer associated with that core. This
+// mapping is updated, lazily, by census_log_start_write().
+//
+// Locking in block struct:
+//
+// Exclusive g_log.lock must be held before calling any functions operating on
+// block structs except census_log_start_write() and census_log_end_write().
+//
+// Writes to a block are serialized via writer_lock. census_log_start_write()
+// acquires this lock and census_log_end_write() releases it. On failure to
+// acquire the lock, writer allocates a new block for the current core and
+// updates core_local_block accordingly.
+//
+// Simultaneous read and write access is allowed. Readers can safely read up to
+// committed bytes (bytes_committed).
+//
+// reader_lock protects the block, currently being read, from getting recycled.
+// start_read() acquires reader_lock and end_read() releases the lock.
+//
+// Read/write access to a block is disabled via try_disable_access(). It returns
+// with both writer_lock and reader_lock held. These locks are subsequently
+// released by enable_access() to enable access to the block.
+//
+// A note on naming: Most function/struct names are prepended by cl_
+// (shorthand for census_log). Further, functions that manipulate structures
+// include the name of the structure, which will be passed as the first
+// argument. E.g. cl_block_initialize() will initialize a cl_block.
+
+#include "src/core/census/mlog.h"
+#include <grpc/support/alloc.h>
+#include <grpc/support/atm.h>
+#include <grpc/support/cpu.h>
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+#include <grpc/support/useful.h>
+#include <stdbool.h>
+#include <string.h>
+
+// End of platform specific code
+
+typedef struct census_log_block_list_struct {
+  struct census_log_block_list_struct* next;
+  struct census_log_block_list_struct* prev;
+  struct census_log_block* block;
+} cl_block_list_struct;
+
+typedef struct census_log_block {
+  // Pointer to underlying buffer.
+  char* buffer;
+  gpr_atm writer_lock;
+  gpr_atm reader_lock;
+  // Keeps completely written bytes. Declared atomic because accessed
+  // simultaneously by reader and writer.
+  gpr_atm bytes_committed;
+  // Bytes already read.
+  size_t bytes_read;
+  // Links for list.
+  cl_block_list_struct link;
+// We want this structure to be cacheline aligned. We assume the following
+// sizes for the various parts on 32/64bit systems:
+// type                 32b size    64b size
+// char*                   4           8
+// 3x gpr_atm             12          24
+// size_t                  4           8
+// cl_block_list_struct   12          24
+// TOTAL                  32          64
+//
+// Depending on the size of our cacheline and the architecture, we
+// selectively add char buffering to this structure. The size is checked
+// via assert in census_log_initialize().
+#if defined(GPR_ARCH_64)
+#define CL_BLOCK_PAD_SIZE (GPR_CACHELINE_SIZE - 64)
+#else
+#if defined(GPR_ARCH_32)
+#define CL_BLOCK_PAD_SIZE (GPR_CACHELINE_SIZE - 32)
+#else
+#error "Unknown architecture"
+#endif
+#endif
+#if CL_BLOCK_PAD_SIZE > 0
+  char padding[CL_BLOCK_PAD_SIZE];
+#endif
+} cl_block;
+
+// A list of cl_blocks, doubly-linked through cl_block::link.
+typedef struct census_log_block_list {
+  int32_t count;            // Number of items in list.
+  cl_block_list_struct ht;  // head/tail of linked list.
+} cl_block_list;
+
+// Cacheline aligned block pointers to avoid false sharing. Block pointer must
+// be initialized via set_block(), before calling other functions
+typedef struct census_log_core_local_block {
+  gpr_atm block;
+// Ensure cachline alignment: we assume sizeof(gpr_atm) == 4 or 8
+#if defined(GPR_ARCH_64)
+#define CL_CORE_LOCAL_BLOCK_PAD_SIZE (GPR_CACHELINE_SIZE - 8)
+#else
+#if defined(GPR_ARCH_32)
+#define CL_CORE_LOCAL_BLOCK_PAD_SIZE (GPR_CACHELINE_SIZE - 4)
+#else
+#error "Unknown architecture"
+#endif
+#endif
+#if CL_CORE_LOCAL_BLOCK_PAD_SIZE > 0
+  char padding[CL_CORE_LOCAL_BLOCK_PAD_SIZE];
+#endif
+} cl_core_local_block;
+
+struct census_log {
+  int discard_old_records;
+  // Number of cores (aka hardware-contexts)
+  unsigned num_cores;
+  // number of CENSUS_LOG_2_MAX_RECORD_SIZE blocks in log
+  uint32_t num_blocks;
+  cl_block* blocks;                        // Block metadata.
+  cl_core_local_block* core_local_blocks;  // Keeps core to block mappings.
+  gpr_mu lock;
+  int initialized;  // has log been initialized?
+  // Keeps the state of the reader iterator. A value of 0 indicates that
+  // iterator has reached the end. census_log_init_reader() resets the value
+  // to num_core to restart iteration.
+  uint32_t read_iterator_state;
+  // Points to the block being read. If non-NULL, the block is locked for
+  // reading(block_being_read_->reader_lock is held).
+  cl_block* block_being_read;
+  char* buffer;
+  cl_block_list free_block_list;
+  cl_block_list dirty_block_list;
+  gpr_atm out_of_space_count;
+};
+
+// Single internal log.
+static struct census_log g_log;
+
+// Functions that operate on an atomic memory location used as a lock.
+
+// Returns non-zero if lock is acquired.
+static int cl_try_lock(gpr_atm* lock) { return gpr_atm_acq_cas(lock, 0, 1); }
+
+static void cl_unlock(gpr_atm* lock) { gpr_atm_rel_store(lock, 0); }
+
+// Functions that operate on cl_core_local_block's.
+
+static void cl_core_local_block_set_block(cl_core_local_block* clb,
+                                          cl_block* block) {
+  gpr_atm_rel_store(&clb->block, (gpr_atm)block);
+}
+
+static cl_block* cl_core_local_block_get_block(cl_core_local_block* clb) {
+  return (cl_block*)gpr_atm_acq_load(&clb->block);
+}
+
+// Functions that operate on cl_block_list_struct's.
+
+static void cl_block_list_struct_initialize(cl_block_list_struct* bls,
+                                            cl_block* block) {
+  bls->next = bls->prev = bls;
+  bls->block = block;
+}
+
+// Functions that operate on cl_block_list's.
+
+static void cl_block_list_initialize(cl_block_list* list) {
+  list->count = 0;
+  cl_block_list_struct_initialize(&list->ht, NULL);
+}
+
+// Returns head of *this, or NULL if empty.
+static cl_block* cl_block_list_head(cl_block_list* list) {
+  return list->ht.next->block;
+}
+
+// Insert element *e after *pos.
+static void cl_block_list_insert(cl_block_list* list, cl_block_list_struct* pos,
+                                 cl_block_list_struct* e) {
+  list->count++;
+  e->next = pos->next;
+  e->prev = pos;
+  e->next->prev = e;
+  e->prev->next = e;
+}
+
+// Insert block at the head of the list
+static void cl_block_list_insert_at_head(cl_block_list* list, cl_block* block) {
+  cl_block_list_insert(list, &list->ht, &block->link);
+}
+
+// Insert block at the tail of the list.
+static void cl_block_list_insert_at_tail(cl_block_list* list, cl_block* block) {
+  cl_block_list_insert(list, list->ht.prev, &block->link);
+}
+
+// Removes block *b. Requires *b be in the list.
+static void cl_block_list_remove(cl_block_list* list, cl_block* b) {
+  list->count--;
+  b->link.next->prev = b->link.prev;
+  b->link.prev->next = b->link.next;
+}
+
+// Functions that operate on cl_block's
+
+static void cl_block_initialize(cl_block* block, char* buffer) {
+  block->buffer = buffer;
+  gpr_atm_rel_store(&block->writer_lock, 0);
+  gpr_atm_rel_store(&block->reader_lock, 0);
+  gpr_atm_rel_store(&block->bytes_committed, 0);
+  block->bytes_read = 0;
+  cl_block_list_struct_initialize(&block->link, block);
+}
+
+// Guards against exposing partially written buffer to the reader.
+static void cl_block_set_bytes_committed(cl_block* block,
+                                         size_t bytes_committed) {
+  gpr_atm_rel_store(&block->bytes_committed, (gpr_atm)bytes_committed);
+}
+
+static size_t cl_block_get_bytes_committed(cl_block* block) {
+  return (size_t)gpr_atm_acq_load(&block->bytes_committed);
+}
+
+// Tries to disable future read/write access to this block. Succeeds if:
+// - no in-progress write AND
+// - no in-progress read AND
+// - 'discard_data' set to true OR no unread data
+// On success, clears the block state and returns with writer_lock_ and
+// reader_lock_ held. These locks are released by a subsequent
+// cl_block_access_enable() call.
+static bool cl_block_try_disable_access(cl_block* block, int discard_data) {
+  if (!cl_try_lock(&block->writer_lock)) {
+    return false;
+  }
+  if (!cl_try_lock(&block->reader_lock)) {
+    cl_unlock(&block->writer_lock);
+    return false;
+  }
+  if (!discard_data &&
+      (block->bytes_read != cl_block_get_bytes_committed(block))) {
+    cl_unlock(&block->reader_lock);
+    cl_unlock(&block->writer_lock);
+    return false;
+  }
+  cl_block_set_bytes_committed(block, 0);
+  block->bytes_read = 0;
+  return true;
+}
+
+static void cl_block_enable_access(cl_block* block) {
+  cl_unlock(&block->reader_lock);
+  cl_unlock(&block->writer_lock);
+}
+
+// Returns with writer_lock held.
+static void* cl_block_start_write(cl_block* block, size_t size) {
+  if (!cl_try_lock(&block->writer_lock)) {
+    return NULL;
+  }
+  size_t bytes_committed = cl_block_get_bytes_committed(block);
+  if (bytes_committed + size > CENSUS_LOG_MAX_RECORD_SIZE) {
+    cl_unlock(&block->writer_lock);
+    return NULL;
+  }
+  return block->buffer + bytes_committed;
+}
+
+// Releases writer_lock and increments committed bytes by 'bytes_written'.
+// 'bytes_written' must be <= 'size' specified in the corresponding
+// StartWrite() call. This function is thread-safe.
+static void cl_block_end_write(cl_block* block, size_t bytes_written) {
+  cl_block_set_bytes_committed(
+      block, cl_block_get_bytes_committed(block) + bytes_written);
+  cl_unlock(&block->writer_lock);
+}
+
+// Returns a pointer to the first unread byte in buffer. The number of bytes
+// available are returned in 'bytes_available'. Acquires reader lock that is
+// released by a subsequent cl_block_end_read() call. Returns NULL if:
+// - read in progress
+// - no data available
+static void* cl_block_start_read(cl_block* block, size_t* bytes_available) {
+  if (!cl_try_lock(&block->reader_lock)) {
+    return NULL;
+  }
+  // bytes_committed may change from under us. Use bytes_available to update
+  // bytes_read below.
+  size_t bytes_committed = cl_block_get_bytes_committed(block);
+  GPR_ASSERT(bytes_committed >= block->bytes_read);
+  *bytes_available = bytes_committed - block->bytes_read;
+  if (*bytes_available == 0) {
+    cl_unlock(&block->reader_lock);
+    return NULL;
+  }
+  void* record = block->buffer + block->bytes_read;
+  block->bytes_read += *bytes_available;
+  return record;
+}
+
+static void cl_block_end_read(cl_block* block) {
+  cl_unlock(&block->reader_lock);
+}
+
+// Internal functions operating on g_log
+
+// Allocates a new free block (or recycles an available dirty block if log is
+// configured to discard old records). Returns NULL if out-of-space.
+static cl_block* cl_allocate_block(void) {
+  cl_block* block = cl_block_list_head(&g_log.free_block_list);
+  if (block != NULL) {
+    cl_block_list_remove(&g_log.free_block_list, block);
+    return block;
+  }
+  if (!g_log.discard_old_records) {
+    // No free block and log is configured to keep old records.
+    return NULL;
+  }
+  // Recycle dirty block. Start from the oldest.
+  for (block = cl_block_list_head(&g_log.dirty_block_list); block != NULL;
+       block = block->link.next->block) {
+    if (cl_block_try_disable_access(block, 1 /* discard data */)) {
+      cl_block_list_remove(&g_log.dirty_block_list, block);
+      return block;
+    }
+  }
+  return NULL;
+}
+
+// Allocates a new block and updates core id => block mapping. 'old_block'
+// points to the block that the caller thinks is attached to
+// 'core_id'. 'old_block' may be NULL. Returns true if:
+// - allocated a new block OR
+// - 'core_id' => 'old_block' mapping changed (another thread allocated a
+//   block before lock was acquired).
+static bool cl_allocate_core_local_block(uint32_t core_id,
+                                         cl_block* old_block) {
+  // Now that we have the lock, check if core-local mapping has changed.
+  cl_core_local_block* core_local_block = &g_log.core_local_blocks[core_id];
+  cl_block* block = cl_core_local_block_get_block(core_local_block);
+  if ((block != NULL) && (block != old_block)) {
+    return true;
+  }
+  if (block != NULL) {
+    cl_core_local_block_set_block(core_local_block, NULL);
+    cl_block_list_insert_at_tail(&g_log.dirty_block_list, block);
+  }
+  block = cl_allocate_block();
+  if (block == NULL) {
+    return false;
+  }
+  cl_core_local_block_set_block(core_local_block, block);
+  cl_block_enable_access(block);
+  return true;
+}
+
+static cl_block* cl_get_block(void* record) {
+  uintptr_t p = (uintptr_t)((char*)record - g_log.buffer);
+  uintptr_t index = p >> CENSUS_LOG_2_MAX_RECORD_SIZE;
+  return &g_log.blocks[index];
+}
+
+// Gets the next block to read and tries to free 'prev' block (if not NULL).
+// Returns NULL if reached the end.
+static cl_block* cl_next_block_to_read(cl_block* prev) {
+  cl_block* block = NULL;
+  if (g_log.read_iterator_state == g_log.num_cores) {
+    // We are traversing dirty list; find the next dirty block.
+    if (prev != NULL) {
+      // Try to free the previous block if there is no unread data. This
+      // block
+      // may have unread data if previously incomplete record completed
+      // between
+      // read_next() calls.
+      block = prev->link.next->block;
+      if (cl_block_try_disable_access(prev, 0 /* do not discard data */)) {
+        cl_block_list_remove(&g_log.dirty_block_list, prev);
+        cl_block_list_insert_at_head(&g_log.free_block_list, prev);
+      }
+    } else {
+      block = cl_block_list_head(&g_log.dirty_block_list);
+    }
+    if (block != NULL) {
+      return block;
+    }
+    // We are done with the dirty list; moving on to core-local blocks.
+  }
+  while (g_log.read_iterator_state > 0) {
+    g_log.read_iterator_state--;
+    block = cl_core_local_block_get_block(
+        &g_log.core_local_blocks[g_log.read_iterator_state]);
+    if (block != NULL) {
+      return block;
+    }
+  }
+  return NULL;
+}
+
+#define CL_LOG_2_MB 20  // 2^20 = 1MB
+
+// External functions: primary stats_log interface
+void census_log_initialize(size_t size_in_mb, int discard_old_records) {
+  // Check cacheline alignment.
+  GPR_ASSERT(sizeof(cl_block) % GPR_CACHELINE_SIZE == 0);
+  GPR_ASSERT(sizeof(cl_core_local_block) % GPR_CACHELINE_SIZE == 0);
+  GPR_ASSERT(!g_log.initialized);
+  g_log.discard_old_records = discard_old_records;
+  g_log.num_cores = gpr_cpu_num_cores();
+  // Ensure that we will not get any overflow in calaculating num_blocks
+  GPR_ASSERT(CL_LOG_2_MB >= CENSUS_LOG_2_MAX_RECORD_SIZE);
+  GPR_ASSERT(size_in_mb < 1000);
+  // Ensure at least 2x as many blocks as there are cores.
+  g_log.num_blocks =
+      (uint32_t)GPR_MAX(2 * g_log.num_cores, (size_in_mb << CL_LOG_2_MB) >>
+                                                 CENSUS_LOG_2_MAX_RECORD_SIZE);
+  gpr_mu_init(&g_log.lock);
+  g_log.read_iterator_state = 0;
+  g_log.block_being_read = NULL;
+  g_log.core_local_blocks = (cl_core_local_block*)gpr_malloc_aligned(
+      g_log.num_cores * sizeof(cl_core_local_block), GPR_CACHELINE_SIZE_LOG);
+  memset(g_log.core_local_blocks, 0,
+         g_log.num_cores * sizeof(cl_core_local_block));
+  g_log.blocks = (cl_block*)gpr_malloc_aligned(
+      g_log.num_blocks * sizeof(cl_block), GPR_CACHELINE_SIZE_LOG);
+  memset(g_log.blocks, 0, g_log.num_blocks * sizeof(cl_block));
+  g_log.buffer = gpr_malloc(g_log.num_blocks * CENSUS_LOG_MAX_RECORD_SIZE);
+  memset(g_log.buffer, 0, g_log.num_blocks * CENSUS_LOG_MAX_RECORD_SIZE);
+  cl_block_list_initialize(&g_log.free_block_list);
+  cl_block_list_initialize(&g_log.dirty_block_list);
+  for (uint32_t i = 0; i < g_log.num_blocks; ++i) {
+    cl_block* block = g_log.blocks + i;
+    cl_block_initialize(block, g_log.buffer + (CENSUS_LOG_MAX_RECORD_SIZE * i));
+    cl_block_try_disable_access(block, 1 /* discard data */);
+    cl_block_list_insert_at_tail(&g_log.free_block_list, block);
+  }
+  gpr_atm_rel_store(&g_log.out_of_space_count, 0);
+  g_log.initialized = 1;
+}
+
+void census_log_shutdown(void) {
+  GPR_ASSERT(g_log.initialized);
+  gpr_mu_destroy(&g_log.lock);
+  gpr_free_aligned(g_log.core_local_blocks);
+  g_log.core_local_blocks = NULL;
+  gpr_free_aligned(g_log.blocks);
+  g_log.blocks = NULL;
+  gpr_free(g_log.buffer);
+  g_log.buffer = NULL;
+  g_log.initialized = 0;
+}
+
+void* census_log_start_write(size_t size) {
+  // Used to bound number of times block allocation is attempted.
+  GPR_ASSERT(size > 0);
+  GPR_ASSERT(g_log.initialized);
+  if (size > CENSUS_LOG_MAX_RECORD_SIZE) {
+    return NULL;
+  }
+  uint32_t attempts_remaining = g_log.num_blocks;
+  uint32_t core_id = gpr_cpu_current_cpu();
+  do {
+    void* record = NULL;
+    cl_block* block =
+        cl_core_local_block_get_block(&g_log.core_local_blocks[core_id]);
+    if (block && (record = cl_block_start_write(block, size))) {
+      return record;
+    }
+    // Need to allocate a new block. We are here if:
+    // - No block associated with the core OR
+    // - Write in-progress on the block OR
+    // - block is out of space
+    gpr_mu_lock(&g_log.lock);
+    bool allocated = cl_allocate_core_local_block(core_id, block);
+    gpr_mu_unlock(&g_log.lock);
+    if (!allocated) {
+      gpr_atm_no_barrier_fetch_add(&g_log.out_of_space_count, 1);
+      return NULL;
+    }
+  } while (attempts_remaining--);
+  // Give up.
+  gpr_atm_no_barrier_fetch_add(&g_log.out_of_space_count, 1);
+  return NULL;
+}
+
+void census_log_end_write(void* record, size_t bytes_written) {
+  GPR_ASSERT(g_log.initialized);
+  cl_block_end_write(cl_get_block(record), bytes_written);
+}
+
+void census_log_init_reader(void) {
+  GPR_ASSERT(g_log.initialized);
+  gpr_mu_lock(&g_log.lock);
+  // If a block is locked for reading unlock it.
+  if (g_log.block_being_read != NULL) {
+    cl_block_end_read(g_log.block_being_read);
+    g_log.block_being_read = NULL;
+  }
+  g_log.read_iterator_state = g_log.num_cores;
+  gpr_mu_unlock(&g_log.lock);
+}
+
+const void* census_log_read_next(size_t* bytes_available) {
+  GPR_ASSERT(g_log.initialized);
+  gpr_mu_lock(&g_log.lock);
+  if (g_log.block_being_read != NULL) {
+    cl_block_end_read(g_log.block_being_read);
+  }
+  do {
+    g_log.block_being_read = cl_next_block_to_read(g_log.block_being_read);
+    if (g_log.block_being_read != NULL) {
+      void* record =
+          cl_block_start_read(g_log.block_being_read, bytes_available);
+      if (record != NULL) {
+        gpr_mu_unlock(&g_log.lock);
+        return record;
+      }
+    }
+  } while (g_log.block_being_read != NULL);
+  gpr_mu_unlock(&g_log.lock);
+  return NULL;
+}
+
+size_t census_log_remaining_space(void) {
+  GPR_ASSERT(g_log.initialized);
+  size_t space = 0;
+  gpr_mu_lock(&g_log.lock);
+  if (g_log.discard_old_records) {
+    // Remaining space is not meaningful; just return the entire log space.
+    space = g_log.num_blocks << CENSUS_LOG_2_MAX_RECORD_SIZE;
+  } else {
+    GPR_ASSERT(g_log.free_block_list.count >= 0);
+    space = (size_t)g_log.free_block_list.count * CENSUS_LOG_MAX_RECORD_SIZE;
+  }
+  gpr_mu_unlock(&g_log.lock);
+  return space;
+}
+
+int64_t census_log_out_of_space_count(void) {
+  GPR_ASSERT(g_log.initialized);
+  return gpr_atm_acq_load(&g_log.out_of_space_count);
+}
diff --git a/src/core/census/mlog.h b/src/core/census/mlog.h
new file mode 100644
index 0000000000..aaba9e1535
--- /dev/null
+++ b/src/core/census/mlog.h
@@ -0,0 +1,95 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/* A very fast in-memory log, optimized for multiple writers. */
+
+#ifndef GRPC_INTERNAL_CORE_CENSUS_MLOG_H
+#define GRPC_INTERNAL_CORE_CENSUS_MLOG_H
+
+#include <grpc/support/port_platform.h>
+#include <stddef.h>
+
+/* Maximum record size, in bytes. */
+#define CENSUS_LOG_2_MAX_RECORD_SIZE 14 /* 2^14 = 16KB */
+#define CENSUS_LOG_MAX_RECORD_SIZE (1 << CENSUS_LOG_2_MAX_RECORD_SIZE)
+
+/* Initialize the statistics logging subsystem with the given log size. A log
+   size of 0 will result in the smallest possible log for the platform
+   (approximately CENSUS_LOG_MAX_RECORD_SIZE * gpr_cpu_num_cores()). If
+   discard_old_records is non-zero, then new records will displace older ones
+   when the log is full. This function must be called before any other
+   census_log functions.
+*/
+void census_log_initialize(size_t size_in_mb, int discard_old_records);
+
+/* Shutdown the logging subsystem. Caller must ensure that:
+   - no in progress or future call to any census_log functions
+   - no incomplete records
+*/
+void census_log_shutdown(void);
+
+/* Allocates and returns a 'size' bytes record and marks it in use. A
+   subsequent census_log_end_write() marks the record complete. The
+   'bytes_written' census_log_end_write() argument must be <=
+   'size'. Returns NULL if out-of-space AND:
+       - log is configured to keep old records OR
+       - all blocks are pinned by incomplete records.
+*/
+void* census_log_start_write(size_t size);
+
+void census_log_end_write(void* record, size_t bytes_written);
+
+void census_log_init_reader(void);
+
+/* census_log_read_next() iterates over blocks with data and for each block
+   returns a pointer to the first unread byte. The number of bytes that can be
+   read are returned in 'bytes_available'. Reader is expected to read all
+   available data. Reading the data consumes it i.e. it cannot be read again.
+   census_log_read_next() returns NULL if the end is reached i.e last block
+   is read. census_log_init_reader() starts the iteration or aborts the
+   current iteration.
+*/
+const void* census_log_read_next(size_t* bytes_available);
+
+/* Returns estimated remaining space across all blocks, in bytes. If log is
+   configured to discard old records, returns total log space. Otherwise,
+   returns space available in empty blocks (partially filled blocks are
+   treated as full).
+*/
+size_t census_log_remaining_space(void);
+
+/* Returns the number of times gprc_stats_log_start_write() failed due to
+   out-of-space. */
+int64_t census_log_out_of_space_count(void);
+
+#endif /* GRPC_INTERNAL_CORE_CENSUS_LOG_H */
diff --git a/src/core/channel/channel_args.c b/src/core/channel/channel_args.c
index 0427ce0b8d..bae7a90a01 100644
--- a/src/core/channel/channel_args.c
+++ b/src/core/channel/channel_args.c
@@ -37,6 +37,7 @@
 
 #include <grpc/census.h>
 #include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/useful.h>
 
@@ -55,9 +56,8 @@ static grpc_arg copy_arg(const grpc_arg *src) {
       break;
     case GRPC_ARG_POINTER:
       dst.value.pointer = src->value.pointer;
-      dst.value.pointer.p = src->value.pointer.copy
-                                ? src->value.pointer.copy(src->value.pointer.p)
-                                : src->value.pointer.p;
+      dst.value.pointer.p =
+          src->value.pointer.vtable->copy(src->value.pointer.p);
       break;
   }
   return dst;
@@ -94,6 +94,58 @@ grpc_channel_args *grpc_channel_args_merge(const grpc_channel_args *a,
   return grpc_channel_args_copy_and_add(a, b->args, b->num_args);
 }
 
+static int cmp_arg(const grpc_arg *a, const grpc_arg *b) {
+  int c = GPR_ICMP(a->type, b->type);
+  if (c != 0) return c;
+  c = strcmp(a->key, b->key);
+  if (c != 0) return c;
+  switch (a->type) {
+    case GRPC_ARG_STRING:
+      return strcmp(a->value.string, b->value.string);
+    case GRPC_ARG_INTEGER:
+      return GPR_ICMP(a->value.integer, b->value.integer);
+    case GRPC_ARG_POINTER:
+      c = GPR_ICMP(a->value.pointer.p, b->value.pointer.p);
+      if (c != 0) {
+        c = GPR_ICMP(a->value.pointer.vtable, b->value.pointer.vtable);
+        if (c == 0) {
+          c = a->value.pointer.vtable->cmp(a->value.pointer.p,
+                                           b->value.pointer.p);
+        }
+      }
+      return c;
+  }
+  GPR_UNREACHABLE_CODE(return 0);
+}
+
+/* stabilizing comparison function: since channel_args ordering matters for
+ * keys with the same name, we need to preserve that ordering */
+static int cmp_key_stable(const void *ap, const void *bp) {
+  const grpc_arg *const *a = ap;
+  const grpc_arg *const *b = bp;
+  int c = strcmp((*a)->key, (*b)->key);
+  if (c == 0) c = GPR_ICMP(*a, *b);
+  return c;
+}
+
+grpc_channel_args *grpc_channel_args_normalize(const grpc_channel_args *a) {
+  grpc_arg **args = gpr_malloc(sizeof(grpc_arg *) * a->num_args);
+  for (size_t i = 0; i < a->num_args; i++) {
+    args[i] = &a->args[i];
+  }
+  qsort(args, a->num_args, sizeof(grpc_arg *), cmp_key_stable);
+
+  grpc_channel_args *b = gpr_malloc(sizeof(grpc_channel_args));
+  b->num_args = a->num_args;
+  b->args = gpr_malloc(sizeof(grpc_arg) * b->num_args);
+  for (size_t i = 0; i < a->num_args; i++) {
+    b->args[i] = copy_arg(args[i]);
+  }
+
+  gpr_free(args);
+  return b;
+}
+
 void grpc_channel_args_destroy(grpc_channel_args *a) {
   size_t i;
   for (i = 0; i < a->num_args; i++) {
@@ -104,9 +156,7 @@ void grpc_channel_args_destroy(grpc_channel_args *a) {
       case GRPC_ARG_INTEGER:
         break;
       case GRPC_ARG_POINTER:
-        if (a->args[i].value.pointer.destroy) {
-          a->args[i].value.pointer.destroy(a->args[i].value.pointer.p);
-        }
+        a->args[i].value.pointer.vtable->destroy(a->args[i].value.pointer.p);
         break;
     }
     gpr_free(a->args[i].key);
@@ -208,3 +258,14 @@ int grpc_channel_args_compression_algorithm_get_states(
     return (1u << GRPC_COMPRESS_ALGORITHMS_COUNT) - 1; /* All algs. enabled */
   }
 }
+
+int grpc_channel_args_compare(const grpc_channel_args *a,
+                              const grpc_channel_args *b) {
+  int c = GPR_ICMP(a->num_args, b->num_args);
+  if (c != 0) return c;
+  for (size_t i = 0; i < a->num_args; i++) {
+    c = cmp_arg(&a->args[i], &b->args[i]);
+    if (c != 0) return c;
+  }
+  return 0;
+}
diff --git a/src/core/channel/channel_args.h b/src/core/channel/channel_args.h
index 480cc9aec2..b3a7c9f434 100644
--- a/src/core/channel/channel_args.h
+++ b/src/core/channel/channel_args.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -40,6 +40,9 @@
 /* Copy some arguments */
 grpc_channel_args *grpc_channel_args_copy(const grpc_channel_args *src);
 
+/* Copy some arguments, stably sorting keys */
+grpc_channel_args *grpc_channel_args_normalize(const grpc_channel_args *a);
+
 /** Copy some arguments and add the to_add parameter in the end.
    If to_add is NULL, it is equivalent to call grpc_channel_args_copy. */
 grpc_channel_args *grpc_channel_args_copy_and_add(const grpc_channel_args *src,
@@ -85,4 +88,7 @@ grpc_channel_args *grpc_channel_args_compression_algorithm_set_state(
 int grpc_channel_args_compression_algorithm_get_states(
     const grpc_channel_args *a);
 
+int grpc_channel_args_compare(const grpc_channel_args *a,
+                              const grpc_channel_args *b);
+
 #endif /* GRPC_INTERNAL_CORE_CHANNEL_CHANNEL_ARGS_H */
diff --git a/src/core/channel/http_client_filter.c b/src/core/channel/http_client_filter.c
index 43eee046b8..1aa27208c2 100644
--- a/src/core/channel/http_client_filter.c
+++ b/src/core/channel/http_client_filter.c
@@ -127,8 +127,8 @@ static void hc_mutate_op(grpc_call_element *elem,
   if (op->recv_initial_metadata != NULL) {
     /* substitute our callback for the higher callback */
     calld->recv_initial_metadata = op->recv_initial_metadata;
-    calld->on_done_recv = op->on_complete;
-    op->on_complete = &calld->hc_on_recv;
+    calld->on_done_recv = op->recv_initial_metadata_ready;
+    op->recv_initial_metadata_ready = &calld->hc_on_recv;
   }
 }
 
diff --git a/src/core/channel/http_server_filter.c b/src/core/channel/http_server_filter.c
index bb75323933..370f8dbe42 100644
--- a/src/core/channel/http_server_filter.c
+++ b/src/core/channel/http_server_filter.c
@@ -186,8 +186,8 @@ static void hs_mutate_op(grpc_call_element *elem,
   if (op->recv_initial_metadata) {
     /* substitute our callback for the higher callback */
     calld->recv_initial_metadata = op->recv_initial_metadata;
-    calld->on_done_recv = op->on_complete;
-    op->on_complete = &calld->hs_on_recv;
+    calld->on_done_recv = op->recv_initial_metadata_ready;
+    op->recv_initial_metadata_ready = &calld->hs_on_recv;
   }
 }
 
diff --git a/src/core/channel/subchannel_call_holder.c b/src/core/channel/subchannel_call_holder.c
index 3ad9fd9efb..81297c8d44 100644
--- a/src/core/channel/subchannel_call_holder.c
+++ b/src/core/channel/subchannel_call_holder.c
@@ -241,10 +241,8 @@ static void fail_locked(grpc_exec_ctx *exec_ctx,
                         grpc_subchannel_call_holder *holder) {
   size_t i;
   for (i = 0; i < holder->waiting_ops_count; i++) {
-    grpc_exec_ctx_enqueue(exec_ctx, holder->waiting_ops[i].on_complete, false,
-                          NULL);
-    grpc_exec_ctx_enqueue(exec_ctx, holder->waiting_ops[i].recv_message_ready,
-                          false, NULL);
+    grpc_transport_stream_op_finish_with_failure(exec_ctx,
+                                                 &holder->waiting_ops[i]);
   }
   holder->waiting_ops_count = 0;
 }
diff --git a/src/core/client_config/connector.c b/src/core/client_config/connector.c
index 1603ffb8be..aa34aa7fab 100644
--- a/src/core/client_config/connector.c
+++ b/src/core/client_config/connector.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -33,8 +33,9 @@
 
 #include "src/core/client_config/connector.h"
 
-void grpc_connector_ref(grpc_connector* connector) {
+grpc_connector* grpc_connector_ref(grpc_connector* connector) {
   connector->vtable->ref(connector);
+  return connector;
 }
 
 void grpc_connector_unref(grpc_exec_ctx* exec_ctx, grpc_connector* connector) {
diff --git a/src/core/client_config/connector.h b/src/core/client_config/connector.h
index b4482fa2ee..b91eb512c3 100644
--- a/src/core/client_config/connector.h
+++ b/src/core/client_config/connector.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -81,7 +81,7 @@ struct grpc_connector_vtable {
                   grpc_connect_out_args *out_args, grpc_closure *notify);
 };
 
-void grpc_connector_ref(grpc_connector *connector);
+grpc_connector *grpc_connector_ref(grpc_connector *connector);
 void grpc_connector_unref(grpc_exec_ctx *exec_ctx, grpc_connector *connector);
 /** Connect using the connector: max one outstanding call at a time */
 void grpc_connector_connect(grpc_exec_ctx *exec_ctx, grpc_connector *connector,
diff --git a/src/core/client_config/subchannel.c b/src/core/client_config/subchannel.c
index 0a996a1e8b..6599c75dba 100644
--- a/src/core/client_config/subchannel.c
+++ b/src/core/client_config/subchannel.c
@@ -36,16 +36,17 @@
 #include <string.h>
 
 #include <grpc/support/alloc.h>
+#include <grpc/support/avl.h>
 
 #include "src/core/channel/channel_args.h"
 #include "src/core/channel/client_channel.h"
 #include "src/core/channel/connected_channel.h"
 #include "src/core/client_config/initial_connect_string.h"
+#include "src/core/client_config/subchannel_index.h"
 #include "src/core/iomgr/timer.h"
 #include "src/core/profiling/timers.h"
 #include "src/core/surface/channel.h"
 #include "src/core/transport/connectivity_state.h"
-#include "src/core/transport/connectivity_state.h"
 
 #define INTERNAL_REF_BITS 16
 #define STRONG_REF_MASK (~(gpr_atm)((1 << INTERNAL_REF_BITS) - 1))
@@ -94,6 +95,8 @@ struct grpc_subchannel {
   struct sockaddr *addr;
   size_t addr_len;
 
+  grpc_subchannel_key *key;
+
   /** initial string to send to peer */
   gpr_slice initial_connect_string;
 
@@ -207,6 +210,7 @@ static void subchannel_destroy(grpc_exec_ctx *exec_ctx, void *arg,
   grpc_connectivity_state_destroy(exec_ctx, &c->state_tracker);
   grpc_connector_unref(exec_ctx, c->connector);
   grpc_pollset_set_destroy(&c->pollset_set);
+  grpc_subchannel_key_destroy(exec_ctx, c->key);
   gpr_free(c);
 }
 
@@ -222,22 +226,42 @@ static gpr_atm ref_mutate(grpc_subchannel *c, gpr_atm delta,
   return old_val;
 }
 
-void grpc_subchannel_ref(grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+grpc_subchannel *grpc_subchannel_ref(grpc_subchannel *c
+                                         GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
   gpr_atm old_refs;
   old_refs = ref_mutate(c, (1 << INTERNAL_REF_BITS),
                         0 REF_MUTATE_PURPOSE("STRONG_REF"));
   GPR_ASSERT((old_refs & STRONG_REF_MASK) != 0);
+  return c;
 }
 
-void grpc_subchannel_weak_ref(grpc_subchannel *c
-                                  GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+grpc_subchannel *grpc_subchannel_weak_ref(grpc_subchannel *c
+                                              GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
   gpr_atm old_refs;
   old_refs = ref_mutate(c, 1, 0 REF_MUTATE_PURPOSE("WEAK_REF"));
   GPR_ASSERT(old_refs != 0);
+  return c;
+}
+
+grpc_subchannel *grpc_subchannel_ref_from_weak_ref(
+    grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  if (!c) return NULL;
+  for (;;) {
+    gpr_atm old_refs = gpr_atm_acq_load(&c->ref_pair);
+    if (old_refs >= (1 << INTERNAL_REF_BITS)) {
+      gpr_atm new_refs = old_refs + (1 << INTERNAL_REF_BITS);
+      if (gpr_atm_rel_cas(&c->ref_pair, old_refs, new_refs)) {
+        return c;
+      }
+    } else {
+      return NULL;
+    }
+  }
 }
 
 static void disconnect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   grpc_connected_subchannel *con;
+  grpc_subchannel_index_unregister(exec_ctx, c->key, c);
   gpr_mu_lock(&c->mu);
   GPR_ASSERT(!c->disconnected);
   c->disconnected = 1;
@@ -276,10 +300,19 @@ static uint32_t random_seed() {
   return (uint32_t)(gpr_time_to_millis(gpr_now(GPR_CLOCK_MONOTONIC)));
 }
 
-grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
+grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
+                                        grpc_connector *connector,
                                         grpc_subchannel_args *args) {
-  grpc_subchannel *c = gpr_malloc(sizeof(*c));
+  grpc_subchannel_key *key = grpc_subchannel_key_create(connector, args);
+  grpc_subchannel *c = grpc_subchannel_index_find(exec_ctx, key);
+  if (c) {
+    grpc_subchannel_key_destroy(exec_ctx, key);
+    return c;
+  }
+
+  c = gpr_malloc(sizeof(*c));
   memset(c, 0, sizeof(*c));
+  c->key = key;
   gpr_atm_no_barrier_store(&c->ref_pair, 1 << INTERNAL_REF_BITS);
   c->connector = connector;
   grpc_connector_ref(c->connector);
@@ -305,7 +338,8 @@ grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
   grpc_connectivity_state_init(&c->state_tracker, GRPC_CHANNEL_IDLE,
                                "subchannel");
   gpr_mu_init(&c->mu);
-  return c;
+
+  return grpc_subchannel_index_register(exec_ctx, key, c);
 }
 
 static void continue_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
diff --git a/src/core/client_config/subchannel.h b/src/core/client_config/subchannel.h
index 57c7c9dc67..313e63c75c 100644
--- a/src/core/client_config/subchannel.h
+++ b/src/core/client_config/subchannel.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -48,6 +48,8 @@ typedef struct grpc_subchannel_args grpc_subchannel_args;
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
 #define GRPC_SUBCHANNEL_REF(p, r) \
   grpc_subchannel_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(p, r) \
+  grpc_subchannel_ref_from_weak_ref((p), __FILE__, __LINE__, (r))
 #define GRPC_SUBCHANNEL_UNREF(cl, p, r) \
   grpc_subchannel_unref((cl), (p), __FILE__, __LINE__, (r))
 #define GRPC_SUBCHANNEL_WEAK_REF(p, r) \
@@ -66,6 +68,8 @@ typedef struct grpc_subchannel_args grpc_subchannel_args;
   , const char *file, int line, const char *reason
 #else
 #define GRPC_SUBCHANNEL_REF(p, r) grpc_subchannel_ref((p))
+#define GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(p, r) \
+  grpc_subchannel_ref_from_weak_ref((p))
 #define GRPC_SUBCHANNEL_UNREF(cl, p, r) grpc_subchannel_unref((cl), (p))
 #define GRPC_SUBCHANNEL_WEAK_REF(p, r) grpc_subchannel_weak_ref((p))
 #define GRPC_SUBCHANNEL_WEAK_UNREF(cl, p, r) \
@@ -79,13 +83,15 @@ typedef struct grpc_subchannel_args grpc_subchannel_args;
 #define GRPC_SUBCHANNEL_REF_EXTRA_ARGS
 #endif
 
-void grpc_subchannel_ref(grpc_subchannel *channel
-                             GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+grpc_subchannel *grpc_subchannel_ref(grpc_subchannel *channel
+                                         GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+grpc_subchannel *grpc_subchannel_ref_from_weak_ref(
+    grpc_subchannel *channel GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
 void grpc_subchannel_unref(grpc_exec_ctx *exec_ctx,
                            grpc_subchannel *channel
                                GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
-void grpc_subchannel_weak_ref(grpc_subchannel *channel
-                                  GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+grpc_subchannel *grpc_subchannel_weak_ref(grpc_subchannel *channel
+                                              GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
 void grpc_subchannel_weak_unref(grpc_exec_ctx *exec_ctx,
                                 grpc_subchannel *channel
                                     GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
@@ -146,6 +152,8 @@ grpc_call_stack *grpc_subchannel_call_get_call_stack(
     grpc_subchannel_call *subchannel_call);
 
 struct grpc_subchannel_args {
+  /* When updating this struct, also update subchannel_index.c */
+
   /** Channel filters for this channel - wrapped factories will likely
       want to mutate this */
   const grpc_channel_filter **filters;
@@ -159,7 +167,8 @@ struct grpc_subchannel_args {
 };
 
 /** create a subchannel given a connector */
-grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
+grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
+                                        grpc_connector *connector,
                                         grpc_subchannel_args *args);
 
 #endif /* GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_H */
diff --git a/src/core/client_config/subchannel_index.c b/src/core/client_config/subchannel_index.c
new file mode 100644
index 0000000000..f78a7fd588
--- /dev/null
+++ b/src/core/client_config/subchannel_index.c
@@ -0,0 +1,259 @@
+//
+//
+// Copyright 2016, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//
+
+#include "src/core/client_config/subchannel_index.h"
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/avl.h>
+#include <grpc/support/tls.h>
+
+#include "src/core/channel/channel_args.h"
+
+// a map of subchannel_key --> subchannel, used for detecting connections
+// to the same destination in order to share them
+static gpr_avl g_subchannel_index;
+
+static gpr_mu g_mu;
+
+struct grpc_subchannel_key {
+  grpc_connector *connector;
+  grpc_subchannel_args args;
+};
+
+GPR_TLS_DECL(subchannel_index_exec_ctx);
+
+static void enter_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_ASSERT(gpr_tls_get(&subchannel_index_exec_ctx) == 0);
+  gpr_tls_set(&subchannel_index_exec_ctx, (intptr_t)exec_ctx);
+}
+
+static void leave_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_ASSERT(gpr_tls_get(&subchannel_index_exec_ctx) == (intptr_t)exec_ctx);
+  gpr_tls_set(&subchannel_index_exec_ctx, 0);
+}
+
+static grpc_exec_ctx *current_ctx() {
+  grpc_exec_ctx *c = (grpc_exec_ctx *)gpr_tls_get(&subchannel_index_exec_ctx);
+  GPR_ASSERT(c != NULL);
+  return c;
+}
+
+static grpc_subchannel_key *create_key(
+    grpc_connector *connector, grpc_subchannel_args *args,
+    grpc_channel_args *(*copy_channel_args)(const grpc_channel_args *args)) {
+  grpc_subchannel_key *k = gpr_malloc(sizeof(*k));
+  k->connector = grpc_connector_ref(connector);
+  k->args.filter_count = args->filter_count;
+  k->args.filters = gpr_malloc(sizeof(*k->args.filters) * k->args.filter_count);
+  memcpy((grpc_channel_filter *)k->args.filters, args->filters,
+         sizeof(*k->args.filters) * k->args.filter_count);
+  k->args.addr_len = args->addr_len;
+  k->args.addr = gpr_malloc(args->addr_len);
+  memcpy(k->args.addr, args->addr, k->args.addr_len);
+  k->args.args = copy_channel_args(args->args);
+  return k;
+}
+
+grpc_subchannel_key *grpc_subchannel_key_create(grpc_connector *connector,
+                                                grpc_subchannel_args *args) {
+  return create_key(connector, args, grpc_channel_args_normalize);
+}
+
+static grpc_subchannel_key *subchannel_key_copy(grpc_subchannel_key *k) {
+  return create_key(k->connector, &k->args, grpc_channel_args_copy);
+}
+
+static int subchannel_key_compare(grpc_subchannel_key *a,
+                                  grpc_subchannel_key *b) {
+  int c = GPR_ICMP(a->connector, b->connector);
+  if (c != 0) return c;
+  c = GPR_ICMP(a->args.addr_len, b->args.addr_len);
+  if (c != 0) return c;
+  c = GPR_ICMP(a->args.filter_count, b->args.filter_count);
+  if (c != 0) return c;
+  c = memcmp(a->args.addr, b->args.addr, a->args.addr_len);
+  if (c != 0) return c;
+  c = memcmp(a->args.filters, b->args.filters,
+             a->args.filter_count * sizeof(*a->args.filters));
+  return grpc_channel_args_compare(a->args.args, b->args.args);
+}
+
+void grpc_subchannel_key_destroy(grpc_exec_ctx *exec_ctx,
+                                 grpc_subchannel_key *k) {
+  grpc_connector_unref(exec_ctx, k->connector);
+  gpr_free(k->args.addr);
+  gpr_free((grpc_channel_args *)k->args.filters);
+  grpc_channel_args_destroy((grpc_channel_args *)k->args.args);
+  gpr_free(k);
+}
+
+static void sck_avl_destroy(void *p) {
+  grpc_subchannel_key_destroy(current_ctx(), p);
+}
+
+static void *sck_avl_copy(void *p) { return subchannel_key_copy(p); }
+
+static long sck_avl_compare(void *a, void *b) {
+  return subchannel_key_compare(a, b);
+}
+
+static void scv_avl_destroy(void *p) {
+  GRPC_SUBCHANNEL_WEAK_UNREF(current_ctx(), p, "subchannel_index");
+}
+
+static void *scv_avl_copy(void *p) {
+  GRPC_SUBCHANNEL_WEAK_REF(p, "subchannel_index");
+  return p;
+}
+
+static const gpr_avl_vtable subchannel_avl_vtable = {
+    .destroy_key = sck_avl_destroy,
+    .copy_key = sck_avl_copy,
+    .compare_keys = sck_avl_compare,
+    .destroy_value = scv_avl_destroy,
+    .copy_value = scv_avl_copy};
+
+void grpc_subchannel_index_init(void) {
+  g_subchannel_index = gpr_avl_create(&subchannel_avl_vtable);
+  gpr_mu_init(&g_mu);
+}
+
+void grpc_subchannel_index_shutdown(void) {
+  gpr_mu_destroy(&g_mu);
+  gpr_avl_unref(g_subchannel_index);
+}
+
+grpc_subchannel *grpc_subchannel_index_find(grpc_exec_ctx *exec_ctx,
+                                            grpc_subchannel_key *key) {
+  enter_ctx(exec_ctx);
+
+  // Lock, and take a reference to the subchannel index.
+  // We don't need to do the search under a lock as avl's are immutable.
+  gpr_mu_lock(&g_mu);
+  gpr_avl index = gpr_avl_ref(g_subchannel_index);
+  gpr_mu_unlock(&g_mu);
+
+  grpc_subchannel *c =
+      GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(gpr_avl_get(index, key), "index_find");
+  gpr_avl_unref(index);
+
+  leave_ctx(exec_ctx);
+  return c;
+}
+
+grpc_subchannel *grpc_subchannel_index_register(grpc_exec_ctx *exec_ctx,
+                                                grpc_subchannel_key *key,
+                                                grpc_subchannel *constructed) {
+  enter_ctx(exec_ctx);
+
+  grpc_subchannel *c = NULL;
+
+  while (c == NULL) {
+    // Compare and swap loop:
+    // - take a reference to the current index
+    gpr_mu_lock(&g_mu);
+    gpr_avl index = gpr_avl_ref(g_subchannel_index);
+    gpr_mu_unlock(&g_mu);
+
+    // - Check to see if a subchannel already exists
+    c = gpr_avl_get(index, key);
+    if (c != NULL) {
+      // yes -> we're done
+      GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, constructed, "index_register");
+    } else {
+      // no -> update the avl and compare/swap
+      gpr_avl updated =
+          gpr_avl_add(gpr_avl_ref(index), subchannel_key_copy(key),
+                      GRPC_SUBCHANNEL_WEAK_REF(constructed, "index_register"));
+
+      // it may happen (but it's expected to be unlikely)
+      // that some other thread has changed the index:
+      // compare/swap here to check that, and retry as necessary
+      gpr_mu_lock(&g_mu);
+      if (index.root == g_subchannel_index.root) {
+        GPR_SWAP(gpr_avl, updated, g_subchannel_index);
+        c = constructed;
+      }
+      gpr_mu_unlock(&g_mu);
+
+      gpr_avl_unref(updated);
+    }
+    gpr_avl_unref(index);
+  }
+
+  leave_ctx(exec_ctx);
+
+  return c;
+}
+
+void grpc_subchannel_index_unregister(grpc_exec_ctx *exec_ctx,
+                                      grpc_subchannel_key *key,
+                                      grpc_subchannel *constructed) {
+  enter_ctx(exec_ctx);
+
+  bool done = false;
+  while (!done) {
+    // Compare and swap loop:
+    // - take a reference to the current index
+    gpr_mu_lock(&g_mu);
+    gpr_avl index = gpr_avl_ref(g_subchannel_index);
+    gpr_mu_unlock(&g_mu);
+
+    // Check to see if this key still refers to the previously
+    // registered subchannel
+    grpc_subchannel *c = gpr_avl_get(index, key);
+    if (c != constructed) {
+      gpr_avl_unref(index);
+      break;
+    }
+
+    // compare and swap the update (some other thread may have
+    // mutated the index behind us)
+    gpr_avl updated = gpr_avl_remove(gpr_avl_ref(index), key);
+
+    gpr_mu_lock(&g_mu);
+    if (index.root == g_subchannel_index.root) {
+      GPR_SWAP(gpr_avl, updated, g_subchannel_index);
+      done = true;
+    }
+    gpr_mu_unlock(&g_mu);
+
+    gpr_avl_unref(updated);
+    gpr_avl_unref(index);
+  }
+
+  leave_ctx(exec_ctx);
+}
diff --git a/src/core/client_config/subchannel_index.h b/src/core/client_config/subchannel_index.h
new file mode 100644
index 0000000000..095ef17819
--- /dev/null
+++ b/src/core/client_config/subchannel_index.h
@@ -0,0 +1,77 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
+#define GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
+
+#include "src/core/client_config/connector.h"
+#include "src/core/client_config/subchannel.h"
+
+/** \file Provides an index of active subchannels so that they can be
+    shared amongst channels */
+
+typedef struct grpc_subchannel_key grpc_subchannel_key;
+
+/** Create a key that can be used to uniquely identify a subchannel */
+grpc_subchannel_key *grpc_subchannel_key_create(grpc_connector *con,
+                                                grpc_subchannel_args *args);
+
+/** Destroy a subchannel key */
+void grpc_subchannel_key_destroy(grpc_exec_ctx *exec_ctx,
+                                 grpc_subchannel_key *key);
+
+/** Given a subchannel key, find the subchannel registered for it.
+    Returns NULL if no such channel exists.
+    Thread-safe. */
+grpc_subchannel *grpc_subchannel_index_find(grpc_exec_ctx *exec_ctx,
+                                            grpc_subchannel_key *key);
+
+/** Register a subchannel against a key.
+    Takes ownership of \a constructed.
+    Returns the registered subchannel. This may be different from
+    \a constructed in the case of a registration race. */
+grpc_subchannel *grpc_subchannel_index_register(grpc_exec_ctx *exec_ctx,
+                                                grpc_subchannel_key *key,
+                                                grpc_subchannel *constructed);
+
+/** Remove \a constructed as the registered subchannel for \a key. */
+void grpc_subchannel_index_unregister(grpc_exec_ctx *exec_ctx,
+                                      grpc_subchannel_key *key,
+                                      grpc_subchannel *constructed);
+
+/** Initialize the subchannel index (global) */
+void grpc_subchannel_index_init(void);
+/** Shutdown the subchannel index (global) */
+void grpc_subchannel_index_shutdown(void);
+
+#endif /* GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_INDEX_H */
diff --git a/src/core/iomgr/pollset_posix.h b/src/core/iomgr/pollset_posix.h
index b34bb09426..5868b3fa21 100644
--- a/src/core/iomgr/pollset_posix.h
+++ b/src/core/iomgr/pollset_posix.h
@@ -142,6 +142,10 @@ int grpc_pollset_has_workers(grpc_pollset *pollset);
 void grpc_remove_fd_from_all_epoll_sets(int fd);
 
 /* override to allow tests to hook poll() usage */
+/* NOTE: Any changes to grpc_poll_function must take place when the gRPC
+   is certainly not doing any polling anywhere.
+   Otherwise, there might be a race between changing the variable and actually
+   doing a polling operation */
 typedef int (*grpc_poll_function_type)(struct pollfd *, nfds_t, int);
 extern grpc_poll_function_type grpc_poll_function;
 extern grpc_wakeup_fd grpc_global_wakeup_fd;
diff --git a/src/core/iomgr/udp_server.c b/src/core/iomgr/udp_server.c
index fe006c603c..ef548cfe4d 100644
--- a/src/core/iomgr/udp_server.c
+++ b/src/core/iomgr/udp_server.c
@@ -137,7 +137,7 @@ grpc_udp_server *grpc_udp_server_create(void) {
 }
 
 static void finish_shutdown(grpc_exec_ctx *exec_ctx, grpc_udp_server *s) {
-  grpc_exec_ctx_enqueue(exec_ctx, s->shutdown_complete, 1);
+  grpc_exec_ctx_enqueue(exec_ctx, s->shutdown_complete, 1, NULL);
 
   gpr_mu_destroy(&s->mu);
   gpr_cv_destroy(&s->cv);
@@ -146,7 +146,8 @@ static void finish_shutdown(grpc_exec_ctx *exec_ctx, grpc_udp_server *s) {
   gpr_free(s);
 }
 
-static void destroyed_port(grpc_exec_ctx *exec_ctx, void *server, int success) {
+static void destroyed_port(grpc_exec_ctx *exec_ctx, void *server,
+                           bool success) {
   grpc_udp_server *s = server;
   gpr_mu_lock(&s->mu);
   s->destroyed_ports++;
@@ -263,10 +264,10 @@ error:
 }
 
 /* event manager callback when reads are ready */
-static void on_read(grpc_exec_ctx *exec_ctx, void *arg, int success) {
+static void on_read(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
   server_port *sp = arg;
 
-  if (success == 0) {
+  if (!success) {
     gpr_mu_lock(&sp->server->mu);
     if (0 == --sp->server->active_ports) {
       gpr_mu_unlock(&sp->server->mu);
diff --git a/src/core/security/credentials.c b/src/core/security/credentials.c
index afba0079f5..c58574bd6d 100644
--- a/src/core/security/credentials.c
+++ b/src/core/security/credentials.c
@@ -196,14 +196,21 @@ static void *server_credentials_pointer_arg_copy(void *p) {
   return grpc_server_credentials_ref(p);
 }
 
+static int server_credentials_pointer_cmp(void *a, void *b) {
+  return GPR_ICMP(a, b);
+}
+
+static const grpc_arg_pointer_vtable cred_ptr_vtable = {
+    server_credentials_pointer_arg_copy, server_credentials_pointer_arg_destroy,
+    server_credentials_pointer_cmp};
+
 grpc_arg grpc_server_credentials_to_arg(grpc_server_credentials *p) {
   grpc_arg arg;
   memset(&arg, 0, sizeof(grpc_arg));
   arg.type = GRPC_ARG_POINTER;
   arg.key = GRPC_SERVER_CREDENTIALS_ARG;
   arg.value.pointer.p = p;
-  arg.value.pointer.copy = server_credentials_pointer_arg_copy;
-  arg.value.pointer.destroy = server_credentials_pointer_arg_destroy;
+  arg.value.pointer.vtable = &cred_ptr_vtable;
   return arg;
 }
 
diff --git a/src/core/security/security_connector.c b/src/core/security/security_connector.c
index bdccbabfea..b46205323b 100644
--- a/src/core/security/security_connector.c
+++ b/src/core/security/security_connector.c
@@ -202,12 +202,17 @@ static void *connector_pointer_arg_copy(void *p) {
   return GRPC_SECURITY_CONNECTOR_REF(p, "connector_pointer_arg");
 }
 
+static int connector_pointer_cmp(void *a, void *b) { return GPR_ICMP(a, b); }
+
+static const grpc_arg_pointer_vtable connector_pointer_vtable = {
+    connector_pointer_arg_copy, connector_pointer_arg_destroy,
+    connector_pointer_cmp};
+
 grpc_arg grpc_security_connector_to_arg(grpc_security_connector *sc) {
   grpc_arg result;
   result.type = GRPC_ARG_POINTER;
   result.key = GRPC_SECURITY_CONNECTOR_ARG;
-  result.value.pointer.destroy = connector_pointer_arg_destroy;
-  result.value.pointer.copy = connector_pointer_arg_copy;
+  result.value.pointer.vtable = &connector_pointer_vtable;
   result.value.pointer.p = sc;
   return result;
 }
diff --git a/src/core/security/security_context.c b/src/core/security/security_context.c
index 2068c97d78..a71b3bc915 100644
--- a/src/core/security/security_context.c
+++ b/src/core/security/security_context.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -309,14 +309,19 @@ static void *auth_context_pointer_arg_copy(void *p) {
   return GRPC_AUTH_CONTEXT_REF(p, "auth_context_pointer_arg");
 }
 
+static int auth_context_pointer_cmp(void *a, void *b) { return GPR_ICMP(a, b); }
+
+static const grpc_arg_pointer_vtable auth_context_pointer_vtable = {
+    auth_context_pointer_arg_copy, auth_context_pointer_arg_destroy,
+    auth_context_pointer_cmp};
+
 grpc_arg grpc_auth_context_to_arg(grpc_auth_context *p) {
   grpc_arg arg;
   memset(&arg, 0, sizeof(grpc_arg));
   arg.type = GRPC_ARG_POINTER;
   arg.key = GRPC_AUTH_CONTEXT_ARG;
   arg.value.pointer.p = p;
-  arg.value.pointer.copy = auth_context_pointer_arg_copy;
-  arg.value.pointer.destroy = auth_context_pointer_arg_destroy;
+  arg.value.pointer.vtable = &auth_context_pointer_vtable;
   return arg;
 }
 
diff --git a/src/core/security/server_auth_filter.c b/src/core/security/server_auth_filter.c
index 4c78711387..3d8e5e8d35 100644
--- a/src/core/security/server_auth_filter.c
+++ b/src/core/security/server_auth_filter.c
@@ -176,8 +176,8 @@ static void set_recv_ops_md_callbacks(grpc_call_element *elem,
   if (op->recv_initial_metadata != NULL) {
     /* substitute our callback for the higher callback */
     calld->recv_initial_metadata = op->recv_initial_metadata;
-    calld->on_done_recv = op->on_complete;
-    op->on_complete = &calld->auth_on_recv;
+    calld->on_done_recv = op->recv_initial_metadata_ready;
+    op->recv_initial_metadata_ready = &calld->auth_on_recv;
     calld->transport_op = *op;
   }
 }
diff --git a/src/core/support/avl.c b/src/core/support/avl.c
index 9734c9987f..f378b3ee17 100644
--- a/src/core/support/avl.c
+++ b/src/core/support/avl.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -167,7 +167,7 @@ static gpr_avl_node *rotate_right_left(const gpr_avl_vtable *vtable, void *key,
       vtable->copy_key(right->left->key),
       vtable->copy_value(right->left->value),
       new_node(key, value, left, ref_node(right->left->left)),
-      new_node(vtable->copy_key(right->key), vtable->copy_key(right->value),
+      new_node(vtable->copy_key(right->key), vtable->copy_value(right->value),
                ref_node(right->left->right), ref_node(right->right)));
   unref_node(vtable, right);
   return n;
diff --git a/src/core/support/env_linux.c b/src/core/support/env_linux.c
index 442cd8298e..1ca6fa1aff 100644
--- a/src/core/support/env_linux.c
+++ b/src/core/support/env_linux.c
@@ -52,6 +52,7 @@
 #include "src/core/support/string.h"
 
 char *gpr_getenv(const char *name) {
+#if defined(GPR_BACKWARDS_COMPATIBILITY_MODE)
   typedef char *(*getenv_type)(const char *);
   static getenv_type getenv_func = NULL;
   /* Check to see which getenv variant is supported (go from most
@@ -62,6 +63,10 @@ char *gpr_getenv(const char *name) {
   }
   char *result = getenv_func(name);
   return result == NULL ? result : gpr_strdup(result);
+#else
+  char *result = secure_getenv(name);
+  return result == NULL ? result : gpr_strdup(result);
+#endif
 }
 
 void gpr_setenv(const char *name, const char *value) {
diff --git a/src/core/support/time_posix.c b/src/core/support/time_posix.c
index 1f92d7f090..36d75e7da2 100644
--- a/src/core/support/time_posix.c
+++ b/src/core/support/time_posix.c
@@ -86,7 +86,7 @@ gpr_timespec gpr_now(gpr_clock_type clock_type) {
     gpr_precise_clock_now(&ret);
     return ret;
   } else {
-#if defined(__linux__) && !defined(GPR_NO_DIRECT_SYSCALLS)
+#if defined(GPR_BACKWARDS_COMPATIBILITY_MODE) && defined(__linux__)
     /* avoid ABI problems by invoking syscalls directly */
     syscall(SYS_clock_gettime, clockid_for_gpr_clock[clock_type], &now);
 #else
diff --git a/src/core/surface/alarm.c b/src/core/surface/alarm.c
index d753023ca9..fb496f6c47 100644
--- a/src/core/surface/alarm.c
+++ b/src/core/surface/alarm.c
@@ -63,9 +63,9 @@ grpc_alarm *grpc_alarm_create(grpc_completion_queue *cq, gpr_timespec deadline,
   alarm->cq = cq;
   alarm->tag = tag;
 
+  grpc_cq_begin_op(cq, tag);
   grpc_timer_init(&exec_ctx, &alarm->alarm, deadline, alarm_cb, alarm,
                   gpr_now(GPR_CLOCK_MONOTONIC));
-  grpc_cq_begin_op(cq, tag);
   grpc_exec_ctx_finish(&exec_ctx);
   return alarm;
 }
diff --git a/src/core/surface/call.c b/src/core/surface/call.c
index 9495e748b5..1b117aa6b8 100644
--- a/src/core/surface/call.c
+++ b/src/core/surface/call.c
@@ -159,6 +159,9 @@ struct grpc_call {
   uint8_t receiving_message;
   uint8_t received_final_op;
 
+  /* have we received initial metadata */
+  bool has_initial_md_been_received;
+
   batch_control active_batches[MAX_CONCURRENT_BATCHES];
 
   /* first idx: is_receiving, second idx: is_trailing */
@@ -200,6 +203,7 @@ struct grpc_call {
   gpr_slice receiving_slice;
   grpc_closure receiving_slice_ready;
   grpc_closure receiving_stream_ready;
+  grpc_closure receiving_initial_metadata_ready;
   uint32_t test_only_last_message_flags;
 
   union {
@@ -212,6 +216,11 @@ struct grpc_call {
       int *cancelled;
     } server;
   } final_op;
+
+  struct {
+    void *bctlp;
+    bool success;
+  } saved_receiving_stream_ready_ctx;
 };
 
 #define CALL_STACK_FROM_CALL(call) ((grpc_call_stack *)((call) + 1))
@@ -993,6 +1002,94 @@ static void receiving_slice_ready(grpc_exec_ctx *exec_ctx, void *bctlp,
   }
 }
 
+static void process_data_after_md(grpc_exec_ctx *exec_ctx, batch_control *bctl,
+                                  bool success) {
+  grpc_call *call = bctl->call;
+  if (call->receiving_stream == NULL) {
+    *call->receiving_buffer = NULL;
+    call->receiving_message = 0;
+    if (gpr_unref(&bctl->steps_to_complete)) {
+      post_batch_completion(exec_ctx, bctl);
+    }
+  } else if (call->receiving_stream->length >
+             grpc_channel_get_max_message_length(call->channel)) {
+    cancel_with_status(exec_ctx, call, GRPC_STATUS_INTERNAL,
+                       "Max message size exceeded");
+    grpc_byte_stream_destroy(exec_ctx, call->receiving_stream);
+    call->receiving_stream = NULL;
+    *call->receiving_buffer = NULL;
+    call->receiving_message = 0;
+    if (gpr_unref(&bctl->steps_to_complete)) {
+      post_batch_completion(exec_ctx, bctl);
+    }
+  } else {
+    call->test_only_last_message_flags = call->receiving_stream->flags;
+    if ((call->receiving_stream->flags & GRPC_WRITE_INTERNAL_COMPRESS) &&
+        (call->compression_algorithm > GRPC_COMPRESS_NONE)) {
+      *call->receiving_buffer = grpc_raw_compressed_byte_buffer_create(
+          NULL, 0, call->compression_algorithm);
+    } else {
+      *call->receiving_buffer = grpc_raw_byte_buffer_create(NULL, 0);
+    }
+    grpc_closure_init(&call->receiving_slice_ready, receiving_slice_ready,
+                      bctl);
+    continue_receiving_slices(exec_ctx, bctl);
+    /* early out */
+    return;
+  }
+}
+
+static void receiving_stream_ready(grpc_exec_ctx *exec_ctx, void *bctlp,
+                                   bool success) {
+  batch_control *bctl = bctlp;
+  grpc_call *call = bctl->call;
+
+  gpr_mu_lock(&bctl->call->mu);
+  if (bctl->call->has_initial_md_been_received) {
+    gpr_mu_unlock(&bctl->call->mu);
+    process_data_after_md(exec_ctx, bctlp, success);
+  } else {
+    call->saved_receiving_stream_ready_ctx.bctlp = bctlp;
+    call->saved_receiving_stream_ready_ctx.success = success;
+    gpr_mu_unlock(&bctl->call->mu);
+  }
+}
+
+static void receiving_initial_metadata_ready(grpc_exec_ctx *exec_ctx,
+                                             void *bctlp, bool success) {
+  batch_control *bctl = bctlp;
+  grpc_call *call = bctl->call;
+
+  gpr_mu_lock(&call->mu);
+
+  grpc_metadata_batch *md =
+      &call->metadata_batch[1 /* is_receiving */][0 /* is_trailing */];
+  grpc_metadata_batch_filter(md, recv_initial_filter, call);
+  call->has_initial_md_been_received = true;
+
+  if (gpr_time_cmp(md->deadline, gpr_inf_future(md->deadline.clock_type)) !=
+          0 &&
+      !call->is_client) {
+    GPR_TIMER_BEGIN("set_deadline_alarm", 0);
+    set_deadline_alarm(exec_ctx, call, md->deadline);
+    GPR_TIMER_END("set_deadline_alarm", 0);
+  }
+
+  if (call->saved_receiving_stream_ready_ctx.bctlp != NULL) {
+    grpc_closure *saved_rsr_closure = grpc_closure_create(
+        receiving_stream_ready, call->saved_receiving_stream_ready_ctx.bctlp);
+    grpc_exec_ctx_enqueue(exec_ctx, saved_rsr_closure,
+                          call->saved_receiving_stream_ready_ctx.success, NULL);
+    call->saved_receiving_stream_ready_ctx.bctlp = NULL;
+  }
+
+  gpr_mu_unlock(&call->mu);
+
+  if (gpr_unref(&bctl->steps_to_complete)) {
+    post_batch_completion(exec_ctx, bctl);
+  }
+}
+
 static void finish_batch(grpc_exec_ctx *exec_ctx, void *bctlp, bool success) {
   batch_control *bctl = bctlp;
   grpc_call *call = bctl->call;
@@ -1011,19 +1108,6 @@ static void finish_batch(grpc_exec_ctx *exec_ctx, void *bctlp, bool success) {
     grpc_metadata_batch_destroy(
         &call->metadata_batch[0 /* is_receiving */][1 /* is_trailing */]);
   }
-  if (bctl->recv_initial_metadata) {
-    grpc_metadata_batch *md =
-        &call->metadata_batch[1 /* is_receiving */][0 /* is_trailing */];
-    grpc_metadata_batch_filter(md, recv_initial_filter, call);
-
-    if (gpr_time_cmp(md->deadline, gpr_inf_future(md->deadline.clock_type)) !=
-            0 &&
-        !call->is_client) {
-      GPR_TIMER_BEGIN("set_deadline_alarm", 0);
-      set_deadline_alarm(exec_ctx, call, md->deadline);
-      GPR_TIMER_END("set_deadline_alarm", 0);
-    }
-  }
   if (bctl->recv_final_op) {
     grpc_metadata_batch *md =
         &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
@@ -1065,45 +1149,6 @@ static void finish_batch(grpc_exec_ctx *exec_ctx, void *bctlp, bool success) {
   }
 }
 
-static void receiving_stream_ready(grpc_exec_ctx *exec_ctx, void *bctlp,
-                                   bool success) {
-  batch_control *bctl = bctlp;
-  grpc_call *call = bctl->call;
-
-  if (call->receiving_stream == NULL) {
-    *call->receiving_buffer = NULL;
-    call->receiving_message = 0;
-    if (gpr_unref(&bctl->steps_to_complete)) {
-      post_batch_completion(exec_ctx, bctl);
-    }
-  } else if (call->receiving_stream->length >
-             grpc_channel_get_max_message_length(call->channel)) {
-    cancel_with_status(exec_ctx, call, GRPC_STATUS_INTERNAL,
-                       "Max message size exceeded");
-    grpc_byte_stream_destroy(exec_ctx, call->receiving_stream);
-    call->receiving_stream = NULL;
-    *call->receiving_buffer = NULL;
-    call->receiving_message = 0;
-    if (gpr_unref(&bctl->steps_to_complete)) {
-      post_batch_completion(exec_ctx, bctl);
-    }
-  } else {
-    call->test_only_last_message_flags = call->receiving_stream->flags;
-    if ((call->receiving_stream->flags & GRPC_WRITE_INTERNAL_COMPRESS) &&
-        (call->compression_algorithm > GRPC_COMPRESS_NONE)) {
-      *call->receiving_buffer = grpc_raw_compressed_byte_buffer_create(
-          NULL, 0, call->compression_algorithm);
-    } else {
-      *call->receiving_buffer = grpc_raw_byte_buffer_create(NULL, 0);
-    }
-    grpc_closure_init(&call->receiving_slice_ready, receiving_slice_ready,
-                      bctl);
-    continue_receiving_slices(exec_ctx, bctl);
-    /* early out */
-    return;
-  }
-}
-
 static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
                                         grpc_call *call, const grpc_op *ops,
                                         size_t nops, void *notify_tag,
@@ -1273,9 +1318,14 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         }
         call->received_initial_metadata = 1;
         call->buffered_metadata[0] = op->data.recv_initial_metadata;
+        grpc_closure_init(&call->receiving_initial_metadata_ready,
+                          receiving_initial_metadata_ready, bctl);
         bctl->recv_initial_metadata = 1;
         stream_op.recv_initial_metadata =
             &call->metadata_batch[1 /* is_receiving */][0 /* is_trailing */];
+        stream_op.recv_initial_metadata_ready =
+            &call->receiving_initial_metadata_ready;
+        num_completion_callbacks_needed++;
         break;
       case GRPC_OP_RECV_MESSAGE:
         /* Flag validation: currently allow no flags */
diff --git a/src/core/surface/channel_create.c b/src/core/surface/channel_create.c
index 4d4337d288..fd7e20e9cc 100644
--- a/src/core/surface/channel_create.c
+++ b/src/core/surface/channel_create.c
@@ -172,7 +172,7 @@ static grpc_subchannel *subchannel_factory_create_subchannel(
   c->base.vtable = &connector_vtable;
   gpr_ref_init(&c->refs, 1);
   args->args = final_args;
-  s = grpc_subchannel_create(&c->base, args);
+  s = grpc_subchannel_create(exec_ctx, &c->base, args);
   grpc_connector_unref(exec_ctx, &c->base);
   grpc_channel_args_destroy(final_args);
   return s;
diff --git a/src/core/surface/init.c b/src/core/surface/init.c
index e3ab70dba7..a4a53d3ec1 100644
--- a/src/core/surface/init.c
+++ b/src/core/surface/init.c
@@ -46,6 +46,8 @@
 #include "src/core/client_config/resolver_registry.h"
 #include "src/core/client_config/resolvers/dns_resolver.h"
 #include "src/core/client_config/resolvers/sockaddr_resolver.h"
+#include "src/core/client_config/subchannel.h"
+#include "src/core/client_config/subchannel_index.h"
 #include "src/core/debug/trace.h"
 #include "src/core/iomgr/executor.h"
 #include "src/core/iomgr/iomgr.h"
@@ -127,6 +129,7 @@ void grpc_init(void) {
     }
     gpr_timers_global_init();
     grpc_cq_global_init();
+    grpc_subchannel_index_init();
     for (i = 0; i < g_number_of_plugins; i++) {
       if (g_all_of_the_plugins[i].init != NULL) {
         g_all_of_the_plugins[i].init();
@@ -145,6 +148,7 @@ void grpc_shutdown(void) {
     grpc_executor_shutdown();
     grpc_cq_global_shutdown();
     grpc_iomgr_shutdown();
+    grpc_subchannel_index_shutdown();
     census_shutdown();
     gpr_timers_global_destroy();
     grpc_tracer_shutdown();
diff --git a/src/core/surface/lame_client.c b/src/core/surface/lame_client.c
index 705996cad3..537069e984 100644
--- a/src/core/surface/lame_client.c
+++ b/src/core/surface/lame_client.c
@@ -78,8 +78,7 @@ static void lame_start_transport_stream_op(grpc_exec_ctx *exec_ctx,
   } else if (op->recv_trailing_metadata != NULL) {
     fill_metadata(elem, op->recv_trailing_metadata);
   }
-  grpc_exec_ctx_enqueue(exec_ctx, op->on_complete, false, NULL);
-  grpc_exec_ctx_enqueue(exec_ctx, op->recv_message_ready, false, NULL);
+  grpc_transport_stream_op_finish_with_failure(exec_ctx, op);
 }
 
 static char *lame_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
diff --git a/src/core/surface/secure_channel_create.c b/src/core/surface/secure_channel_create.c
index dd1441ad67..9c04426d87 100644
--- a/src/core/surface/secure_channel_create.c
+++ b/src/core/surface/secure_channel_create.c
@@ -238,7 +238,7 @@ static grpc_subchannel *subchannel_factory_create_subchannel(
   gpr_mu_init(&c->mu);
   gpr_ref_init(&c->refs, 1);
   args->args = final_args;
-  s = grpc_subchannel_create(&c->base, args);
+  s = grpc_subchannel_create(exec_ctx, &c->base, args);
   grpc_connector_unref(exec_ctx, &c->base);
   grpc_channel_args_destroy(final_args);
   return s;
diff --git a/src/core/surface/server.c b/src/core/surface/server.c
index 42cffccb4c..fb5e0d4b9e 100644
--- a/src/core/surface/server.c
+++ b/src/core/surface/server.c
@@ -596,8 +596,8 @@ static void server_mutate_op(grpc_call_element *elem,
 
   if (op->recv_initial_metadata != NULL) {
     calld->recv_initial_metadata = op->recv_initial_metadata;
-    calld->on_done_recv_initial_metadata = op->on_complete;
-    op->on_complete = &calld->server_on_recv_initial_metadata;
+    calld->on_done_recv_initial_metadata = op->recv_initial_metadata_ready;
+    op->recv_initial_metadata_ready = &calld->server_on_recv_initial_metadata;
   }
 }
 
diff --git a/src/core/surface/validate_metadata.c b/src/core/surface/validate_metadata.c
index df2e80b4b7..bf4126867f 100644
--- a/src/core/surface/validate_metadata.c
+++ b/src/core/surface/validate_metadata.c
@@ -50,7 +50,7 @@ static int conforms_to(const char *s, size_t len, const uint8_t *legal_bits) {
 
 int grpc_header_key_is_legal(const char *key, size_t length) {
   static const uint8_t legal_header_bits[256 / 8] = {
-      0x00, 0x00, 0x00, 0x00, 0x00, 0x20, 0xff, 0x03, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x60, 0xff, 0x03, 0x00, 0x00, 0x00,
       0x80, 0xfe, 0xff, 0xff, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
       0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
   if (length == 0) {
diff --git a/src/core/surface/version.c b/src/core/surface/version.c
index 19f0983c0f..7723f39401 100644
--- a/src/core/surface/version.c
+++ b/src/core/surface/version.c
@@ -36,4 +36,4 @@
 
 #include <grpc/grpc.h>
 
-const char *grpc_version_string(void) { return "0.13.1-pre1"; }
+const char *grpc_version_string(void) { return "0.14.0-dev"; }
diff --git a/src/core/transport/chttp2/internal.h b/src/core/transport/chttp2/internal.h
index c611496e7e..0e1e2c4265 100644
--- a/src/core/transport/chttp2/internal.h
+++ b/src/core/transport/chttp2/internal.h
@@ -385,7 +385,7 @@ typedef struct {
   grpc_closure *send_trailing_metadata_finished;
 
   grpc_metadata_batch *recv_initial_metadata;
-  grpc_closure *recv_initial_metadata_finished;
+  grpc_closure *recv_initial_metadata_ready;
   grpc_byte_stream **recv_message;
   grpc_closure *recv_message_ready;
   grpc_metadata_batch *recv_trailing_metadata;
diff --git a/src/core/transport/chttp2_transport.c b/src/core/transport/chttp2_transport.c
index 9298573c7f..617d98875c 100644
--- a/src/core/transport/chttp2_transport.c
+++ b/src/core/transport/chttp2_transport.c
@@ -544,7 +544,7 @@ static void destroy_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
   GPR_ASSERT(s->global.send_initial_metadata_finished == NULL);
   GPR_ASSERT(s->global.send_message_finished == NULL);
   GPR_ASSERT(s->global.send_trailing_metadata_finished == NULL);
-  GPR_ASSERT(s->global.recv_initial_metadata_finished == NULL);
+  GPR_ASSERT(s->global.recv_initial_metadata_ready == NULL);
   GPR_ASSERT(s->global.recv_message_ready == NULL);
   GPR_ASSERT(s->global.recv_trailing_metadata_finished == NULL);
   grpc_chttp2_data_parser_destroy(exec_ctx, &s->parsing.data_parser);
@@ -863,9 +863,9 @@ static void perform_stream_op_locked(
   }
 
   if (op->recv_initial_metadata != NULL) {
-    GPR_ASSERT(stream_global->recv_initial_metadata_finished == NULL);
-    stream_global->recv_initial_metadata_finished =
-        add_closure_barrier(on_complete);
+    GPR_ASSERT(stream_global->recv_initial_metadata_ready == NULL);
+    stream_global->recv_initial_metadata_ready =
+        op->recv_initial_metadata_ready;
     stream_global->recv_initial_metadata = op->recv_initial_metadata;
     grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
   }
@@ -1009,13 +1009,14 @@ static void check_read_ops(grpc_exec_ctx *exec_ctx,
   grpc_byte_stream *bs;
   while (
       grpc_chttp2_list_pop_check_read_ops(transport_global, &stream_global)) {
-    if (stream_global->recv_initial_metadata_finished != NULL &&
+    if (stream_global->recv_initial_metadata_ready != NULL &&
         stream_global->published_initial_metadata) {
       grpc_chttp2_incoming_metadata_buffer_publish(
           &stream_global->received_initial_metadata,
           stream_global->recv_initial_metadata);
-      grpc_chttp2_complete_closure_step(
-          exec_ctx, &stream_global->recv_initial_metadata_finished, 1);
+      grpc_exec_ctx_enqueue(
+          exec_ctx, stream_global->recv_initial_metadata_ready, true, NULL);
+      stream_global->recv_initial_metadata_ready = NULL;
     }
     if (stream_global->recv_message_ready != NULL) {
       if (stream_global->incoming_frames.head != NULL) {
diff --git a/src/core/transport/static_metadata.c b/src/core/transport/static_metadata.c
index 233e5c0d92..eeedae0619 100644
--- a/src/core/transport/static_metadata.c
+++ b/src/core/transport/static_metadata.c
@@ -35,11 +35,11 @@
  * WARNING: Auto-generated code.
  *
  * To make changes to this file, change
- *tools/codegen/core/gen_static_metadata.py,
+ * tools/codegen/core/gen_static_metadata.py,
  * and then re-run it.
  *
  * See metadata.h for an explanation of the interface here, and metadata.c for
- *an
+ * an
  * explanation of what's going on.
  */
 
@@ -69,21 +69,21 @@ const char *const grpc_static_metadata_strings[GRPC_STATIC_MDSTR_COUNT] = {
     "0", "1", "2", "200", "204", "206", "304", "400", "404", "500", "accept",
     "accept-charset", "accept-encoding", "accept-language", "accept-ranges",
     "access-control-allow-origin", "age", "allow", "application/grpc",
-    ":authority", "authorization", "cache-control", "census", "census-bin",
-    "content-disposition", "content-encoding", "content-language",
-    "content-length", "content-location", "content-range", "content-type",
-    "cookie", "date", "deflate", "deflate,gzip", "", "etag", "expect",
-    "expires", "from", "GET", "grpc", "grpc-accept-encoding", "grpc-encoding",
-    "grpc-internal-encoding-request", "grpc-message", "grpc-status",
-    "grpc-timeout", "gzip", "gzip, deflate", "host", "http", "https",
-    "identity", "identity,deflate", "identity,deflate,gzip", "identity,gzip",
-    "if-match", "if-modified-since", "if-none-match", "if-range",
-    "if-unmodified-since", "last-modified", "link", "location", "max-forwards",
-    ":method", ":path", "POST", "proxy-authenticate", "proxy-authorization",
-    "range", "referer", "refresh", "retry-after", ":scheme", "server",
-    "set-cookie", "/", "/index.html", ":status", "strict-transport-security",
-    "te", "trailers", "transfer-encoding", "user-agent", "vary", "via",
-    "www-authenticate"};
+    ":authority", "authorization", "cache-control", "census-bin",
+    "census-binary-bin", "content-disposition", "content-encoding",
+    "content-language", "content-length", "content-location", "content-range",
+    "content-type", "cookie", "date", "deflate", "deflate,gzip", "", "etag",
+    "expect", "expires", "from", "GET", "grpc", "grpc-accept-encoding",
+    "grpc-encoding", "grpc-internal-encoding-request", "grpc-message",
+    "grpc-status", "grpc-timeout", "gzip", "gzip, deflate", "host", "http",
+    "https", "identity", "identity,deflate", "identity,deflate,gzip",
+    "identity,gzip", "if-match", "if-modified-since", "if-none-match",
+    "if-range", "if-unmodified-since", "last-modified", "link", "location",
+    "max-forwards", ":method", ":path", "POST", "proxy-authenticate",
+    "proxy-authorization", "range", "referer", "refresh", "retry-after",
+    ":scheme", "server", "set-cookie", "/", "/index.html", ":status",
+    "strict-transport-security", "te", "trailers", "transfer-encoding",
+    "user-agent", "vary", "via", "www-authenticate"};
 
 const uint8_t grpc_static_accept_encoding_metadata[8] = {0,  29, 26, 30,
                                                          28, 32, 27, 31};
diff --git a/src/core/transport/static_metadata.h b/src/core/transport/static_metadata.h
index 3803a0488b..ef72b802b5 100644
--- a/src/core/transport/static_metadata.h
+++ b/src/core/transport/static_metadata.h
@@ -94,10 +94,10 @@ extern grpc_mdstr grpc_static_mdstr_table[GRPC_STATIC_MDSTR_COUNT];
 #define GRPC_MDSTR_AUTHORIZATION (&grpc_static_mdstr_table[20])
 /* "cache-control" */
 #define GRPC_MDSTR_CACHE_CONTROL (&grpc_static_mdstr_table[21])
-/* "census" */
-#define GRPC_MDSTR_CENSUS (&grpc_static_mdstr_table[22])
 /* "census-bin" */
-#define GRPC_MDSTR_CENSUS_BIN (&grpc_static_mdstr_table[23])
+#define GRPC_MDSTR_CENSUS_BIN (&grpc_static_mdstr_table[22])
+/* "census-binary-bin" */
+#define GRPC_MDSTR_CENSUS_BINARY_BIN (&grpc_static_mdstr_table[23])
 /* "content-disposition" */
 #define GRPC_MDSTR_CONTENT_DISPOSITION (&grpc_static_mdstr_table[24])
 /* "content-encoding" */
diff --git a/src/core/transport/transport.c b/src/core/transport/transport.c
index 08d685668c..6e154b629a 100644
--- a/src/core/transport/transport.c
+++ b/src/core/transport/transport.c
@@ -126,6 +126,7 @@ char *grpc_transport_get_peer(grpc_exec_ctx *exec_ctx,
 void grpc_transport_stream_op_finish_with_failure(
     grpc_exec_ctx *exec_ctx, grpc_transport_stream_op *op) {
   grpc_exec_ctx_enqueue(exec_ctx, op->recv_message_ready, false, NULL);
+  grpc_exec_ctx_enqueue(exec_ctx, op->recv_initial_metadata_ready, false, NULL);
   grpc_exec_ctx_enqueue(exec_ctx, op->on_complete, false, NULL);
 }
 
diff --git a/src/core/transport/transport.h b/src/core/transport/transport.h
index f5cac77adc..8902c5d2f6 100644
--- a/src/core/transport/transport.h
+++ b/src/core/transport/transport.h
@@ -92,6 +92,8 @@ typedef struct grpc_transport_stream_op {
 
   /** Receive initial metadata from the stream, into provided metadata batch. */
   grpc_metadata_batch *recv_initial_metadata;
+  /** Should be enqueued when initial metadata is ready to be processed. */
+  grpc_closure *recv_initial_metadata_ready;
 
   /** Receive message data from the stream, into provided byte stream. */
   grpc_byte_stream **recv_message;
@@ -103,7 +105,8 @@ typedef struct grpc_transport_stream_op {
   grpc_metadata_batch *recv_trailing_metadata;
 
   /** Should be enqueued when all requested operations (excluding recv_message
-     which has its own closure) in a given batch have been completed. */
+      and recv_initial_metadata which have their own closures) in a given batch
+      have been completed. */
   grpc_closure *on_complete;
 
   /** If != GRPC_STATUS_OK, cancel this stream */
diff --git a/src/cpp/client/create_channel.cc b/src/cpp/client/create_channel.cc
index fdaa28ffef..76a1b31e2f 100644
--- a/src/cpp/client/create_channel.cc
+++ b/src/cpp/client/create_channel.cc
@@ -32,7 +32,6 @@
  */
 
 #include <memory>
-#include <sstream>
 
 #include <grpc++/channel.h>
 #include <grpc++/create_channel.h>
@@ -56,13 +55,8 @@ std::shared_ptr<Channel> CreateCustomChannel(
     const ChannelArguments& args) {
   internal::GrpcLibrary
       init_lib;  // We need to call init in case of a bad creds.
-  ChannelArguments cp_args = args;
-  std::ostringstream user_agent_prefix;
-  user_agent_prefix << "grpc-c++/" << grpc_version_string();
-  cp_args.SetString(GRPC_ARG_PRIMARY_USER_AGENT_STRING,
-                    user_agent_prefix.str());
   return creds
-             ? creds->CreateChannel(target, cp_args)
+             ? creds->CreateChannel(target, args)
              : CreateChannelInternal("", grpc_lame_client_channel_create(
                                              NULL, GRPC_STATUS_INVALID_ARGUMENT,
                                              "Invalid credentials."));
diff --git a/src/cpp/common/alarm.cc b/src/cpp/common/alarm.cc
index 807a67df24..a289688768 100644
--- a/src/cpp/common/alarm.cc
+++ b/src/cpp/common/alarm.cc
@@ -39,7 +39,8 @@ namespace grpc {
 
 static internal::GrpcLibraryInitializer g_gli_initializer;
 Alarm::Alarm(CompletionQueue* cq, gpr_timespec deadline, void* tag)
-    : alarm_(grpc_alarm_create(cq->cq(), deadline, tag)) {
+    : tag_(tag),
+      alarm_(grpc_alarm_create(cq->cq(), deadline, static_cast<void*>(&tag_))) {
   g_gli_initializer.summon();
 }
 
diff --git a/src/cpp/common/channel_arguments.cc b/src/cpp/common/channel_arguments.cc
index 90cd5136af..d7faa5e173 100644
--- a/src/cpp/common/channel_arguments.cc
+++ b/src/cpp/common/channel_arguments.cc
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -30,14 +30,23 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
-
 #include <grpc++/support/channel_arguments.h>
 
+#include <sstream>
+
+#include <grpc/impl/codegen/grpc_types.h>
 #include <grpc/support/log.h>
 #include "src/core/channel/channel_args.h"
 
 namespace grpc {
 
+ChannelArguments::ChannelArguments() {
+  std::ostringstream user_agent_prefix;
+  user_agent_prefix << "grpc-c++/" << grpc_version_string();
+  // This will be ignored if used on the server side.
+  SetString(GRPC_ARG_PRIMARY_USER_AGENT_STRING, user_agent_prefix.str());
+}
+
 ChannelArguments::ChannelArguments(const ChannelArguments& other)
     : strings_(other.strings_) {
   args_.reserve(other.args_.size());
@@ -62,9 +71,7 @@ ChannelArguments::ChannelArguments(const ChannelArguments& other)
         break;
       case GRPC_ARG_POINTER:
         ap.value.pointer = a->value.pointer;
-        ap.value.pointer.p = a->value.pointer.copy
-                                 ? a->value.pointer.copy(ap.value.pointer.p)
-                                 : ap.value.pointer.p;
+        ap.value.pointer.p = a->value.pointer.vtable->copy(ap.value.pointer.p);
         break;
     }
     args_.push_back(ap);
@@ -81,6 +88,31 @@ void ChannelArguments::SetCompressionAlgorithm(
   SetInt(GRPC_COMPRESSION_ALGORITHM_ARG, algorithm);
 }
 
+// Note: a second call to this will add in front the result of the first call.
+// An example is calling this on a copy of ChannelArguments which already has a
+// prefix. The user can build up a prefix string by calling this multiple times,
+// each with more significant identifier.
+void ChannelArguments::SetUserAgentPrefix(
+    const grpc::string& user_agent_prefix) {
+  if (user_agent_prefix.empty()) {
+    return;
+  }
+  bool replaced = false;
+  for (auto it = args_.begin(); it != args_.end(); ++it) {
+    const grpc_arg& arg = *it;
+    if (arg.type == GRPC_ARG_STRING &&
+        grpc::string(arg.key) == GRPC_ARG_PRIMARY_USER_AGENT_STRING) {
+      strings_.push_back(user_agent_prefix + " " + arg.value.string);
+      it->value.string = const_cast<char*>(strings_.back().c_str());
+      replaced = true;
+      break;
+    }
+  }
+  if (!replaced) {
+    SetString(GRPC_ARG_PRIMARY_USER_AGENT_STRING, user_agent_prefix);
+  }
+}
+
 void ChannelArguments::SetInt(const grpc::string& key, int value) {
   grpc_arg arg;
   arg.type = GRPC_ARG_INTEGER;
@@ -92,13 +124,15 @@ void ChannelArguments::SetInt(const grpc::string& key, int value) {
 }
 
 void ChannelArguments::SetPointer(const grpc::string& key, void* value) {
+  static const grpc_arg_pointer_vtable vtable = {
+      &PointerVtableMembers::Copy, &PointerVtableMembers::Destroy,
+      &PointerVtableMembers::Compare};
   grpc_arg arg;
   arg.type = GRPC_ARG_POINTER;
   strings_.push_back(key);
   arg.key = const_cast<char*>(strings_.back().c_str());
   arg.value.pointer.p = value;
-  arg.value.pointer.copy = nullptr;
-  arg.value.pointer.destroy = nullptr;
+  arg.value.pointer.vtable = &vtable;
   args_.push_back(arg);
 }
 
diff --git a/src/cpp/server/server_builder.cc b/src/cpp/server/server_builder.cc
index a8c188e5a5..c54cf6474f 100644
--- a/src/cpp/server/server_builder.cc
+++ b/src/cpp/server/server_builder.cc
@@ -38,7 +38,6 @@
 #include <grpc++/impl/service_type.h>
 #include <grpc++/server.h>
 #include "src/cpp/server/thread_pool_interface.h"
-#include "src/cpp/server/fixed_size_thread_pool.h"
 
 namespace grpc {
 
diff --git a/src/csharp/Grpc.Auth/GoogleAuthInterceptors.cs b/src/csharp/Grpc.Auth/GoogleAuthInterceptors.cs
index f77e9c6573..1837f5c74b 100644
--- a/src/csharp/Grpc.Auth/GoogleAuthInterceptors.cs
+++ b/src/csharp/Grpc.Auth/GoogleAuthInterceptors.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -71,7 +71,7 @@ namespace Grpc.Auth
         /// <returns>The interceptor.</returns>
         public static AsyncAuthInterceptor FromAccessToken(string accessToken)
         {
-            Preconditions.CheckNotNull(accessToken);
+            GrpcPreconditions.CheckNotNull(accessToken);
             return new AsyncAuthInterceptor(async (context, metadata) =>
             {
                 metadata.Add(CreateBearerTokenHeader(accessToken));
diff --git a/src/csharp/Grpc.Core/AsyncAuthInterceptor.cs b/src/csharp/Grpc.Core/AsyncAuthInterceptor.cs
index 5c9ab04812..5ba06d6509 100644
--- a/src/csharp/Grpc.Core/AsyncAuthInterceptor.cs
+++ b/src/csharp/Grpc.Core/AsyncAuthInterceptor.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -61,8 +61,8 @@ namespace Grpc.Core
         /// </summary>
         public AuthInterceptorContext(string serviceUrl, string methodName)
         {
-            this.serviceUrl = Preconditions.CheckNotNull(serviceUrl);
-            this.methodName = Preconditions.CheckNotNull(methodName);
+            this.serviceUrl = GrpcPreconditions.CheckNotNull(serviceUrl);
+            this.methodName = GrpcPreconditions.CheckNotNull(methodName);
         }
 
         /// <summary>
diff --git a/src/csharp/Grpc.Core/CallCredentials.cs b/src/csharp/Grpc.Core/CallCredentials.cs
index a71c8904fe..7cd41d0480 100644
--- a/src/csharp/Grpc.Core/CallCredentials.cs
+++ b/src/csharp/Grpc.Core/CallCredentials.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -87,7 +87,7 @@ namespace Grpc.Core
         /// <param name="interceptor">authentication interceptor</param>
         public MetadataCredentials(AsyncAuthInterceptor interceptor)
         {
-            this.interceptor = Preconditions.CheckNotNull(interceptor);
+            this.interceptor = GrpcPreconditions.CheckNotNull(interceptor);
         }
 
         internal override CallCredentialsSafeHandle ToNativeCredentials()
@@ -111,7 +111,7 @@ namespace Grpc.Core
         /// <param name="credentials">credentials to compose</param>
         public CompositeCallCredentials(params CallCredentials[] credentials)
         {
-            Preconditions.CheckArgument(credentials.Length >= 2, "Composite credentials object can only be created from 2 or more credentials.");
+            GrpcPreconditions.CheckArgument(credentials.Length >= 2, "Composite credentials object can only be created from 2 or more credentials.");
             this.credentials = new List<CallCredentials>(credentials);
         }
 
diff --git a/src/csharp/Grpc.Core/CallInvocationDetails.cs b/src/csharp/Grpc.Core/CallInvocationDetails.cs
index 8228b8f317..52bfbe6edb 100644
--- a/src/csharp/Grpc.Core/CallInvocationDetails.cs
+++ b/src/csharp/Grpc.Core/CallInvocationDetails.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -85,11 +85,11 @@ namespace Grpc.Core
         /// <param name="options">Call options.</param>
         public CallInvocationDetails(Channel channel, string method, string host, Marshaller<TRequest> requestMarshaller, Marshaller<TResponse> responseMarshaller, CallOptions options)
         {
-            this.channel = Preconditions.CheckNotNull(channel, "channel");
-            this.method = Preconditions.CheckNotNull(method, "method");
+            this.channel = GrpcPreconditions.CheckNotNull(channel, "channel");
+            this.method = GrpcPreconditions.CheckNotNull(method, "method");
             this.host = host;
-            this.requestMarshaller = Preconditions.CheckNotNull(requestMarshaller, "requestMarshaller");
-            this.responseMarshaller = Preconditions.CheckNotNull(responseMarshaller, "responseMarshaller");
+            this.requestMarshaller = GrpcPreconditions.CheckNotNull(requestMarshaller, "requestMarshaller");
+            this.responseMarshaller = GrpcPreconditions.CheckNotNull(responseMarshaller, "responseMarshaller");
             this.options = options;
         }
 
diff --git a/src/csharp/Grpc.Core/CallOptions.cs b/src/csharp/Grpc.Core/CallOptions.cs
index 1fda80cb90..7bd95d4ba8 100644
--- a/src/csharp/Grpc.Core/CallOptions.cs
+++ b/src/csharp/Grpc.Core/CallOptions.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -176,13 +176,13 @@ namespace Grpc.Core
             {
                 if (propagationToken.Options.IsPropagateDeadline)
                 {
-                    Preconditions.CheckArgument(!newOptions.deadline.HasValue,
+                    GrpcPreconditions.CheckArgument(!newOptions.deadline.HasValue,
                         "Cannot propagate deadline from parent call. The deadline has already been set explicitly.");
                     newOptions.deadline = propagationToken.ParentDeadline;
                 }
                 if (propagationToken.Options.IsPropagateCancellation)
                 {
-                    Preconditions.CheckArgument(!newOptions.cancellationToken.CanBeCanceled,
+                    GrpcPreconditions.CheckArgument(!newOptions.cancellationToken.CanBeCanceled,
                         "Cannot propagate cancellation token from parent call. The cancellation token has already been set to a non-default value.");
                     newOptions.cancellationToken = propagationToken.ParentCancellationToken;
                 }
diff --git a/src/csharp/Grpc.Core/Channel.cs b/src/csharp/Grpc.Core/Channel.cs
index d8d43c7998..d7a482d86f 100644
--- a/src/csharp/Grpc.Core/Channel.cs
+++ b/src/csharp/Grpc.Core/Channel.cs
@@ -1,5 +1,5 @@
 #region Copyright notice and license
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -68,7 +68,7 @@ namespace Grpc.Core
         /// <param name="options">Channel options.</param>
         public Channel(string target, ChannelCredentials credentials, IEnumerable<ChannelOption> options = null)
         {
-            this.target = Preconditions.CheckNotNull(target, "target");
+            this.target = GrpcPreconditions.CheckNotNull(target, "target");
             this.options = CreateOptionsDictionary(options);
             EnsureUserAgentChannelOption(this.options);
             this.environment = GrpcEnvironment.AddRef();
@@ -117,7 +117,7 @@ namespace Grpc.Core
         /// </summary>
         public Task WaitForStateChangedAsync(ChannelState lastObservedState, DateTime? deadline = null)
         {
-            Preconditions.CheckArgument(lastObservedState != ChannelState.FatalFailure,
+            GrpcPreconditions.CheckArgument(lastObservedState != ChannelState.FatalFailure,
                 "FatalFailure is a terminal state. No further state changes can occur.");
             var tcs = new TaskCompletionSource<object>();
             var deadlineTimespec = deadline.HasValue ? Timespec.FromDateTime(deadline.Value) : Timespec.InfFuture;
@@ -184,7 +184,7 @@ namespace Grpc.Core
         {
             lock (myLock)
             {
-                Preconditions.CheckState(!shutdownRequested);
+                GrpcPreconditions.CheckState(!shutdownRequested);
                 shutdownRequested = true;
             }
 
@@ -221,7 +221,7 @@ namespace Grpc.Core
 
             bool success = false;
             handle.DangerousAddRef(ref success);
-            Preconditions.CheckState(success);
+            GrpcPreconditions.CheckState(success);
         }
 
         internal void RemoveCallReference(object call)
diff --git a/src/csharp/Grpc.Core/ChannelCredentials.cs b/src/csharp/Grpc.Core/ChannelCredentials.cs
index 5d96958e7c..03cda28400 100644
--- a/src/csharp/Grpc.Core/ChannelCredentials.cs
+++ b/src/csharp/Grpc.Core/ChannelCredentials.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -183,9 +183,9 @@ namespace Grpc.Core
         /// <param name="callCredentials">channelCredentials to compose</param>
         public CompositeChannelCredentials(ChannelCredentials channelCredentials, CallCredentials callCredentials)
         {
-            this.channelCredentials = Preconditions.CheckNotNull(channelCredentials);
-            this.callCredentials = Preconditions.CheckNotNull(callCredentials);
-            Preconditions.CheckArgument(channelCredentials.IsComposable, "Supplied channel credentials do not allow composition.");
+            this.channelCredentials = GrpcPreconditions.CheckNotNull(channelCredentials);
+            this.callCredentials = GrpcPreconditions.CheckNotNull(callCredentials);
+            GrpcPreconditions.CheckArgument(channelCredentials.IsComposable, "Supplied channel credentials do not allow composition.");
         }
 
         internal override ChannelCredentialsSafeHandle ToNativeCredentials()
diff --git a/src/csharp/Grpc.Core/ChannelOptions.cs b/src/csharp/Grpc.Core/ChannelOptions.cs
index d70673cf78..65e15e21e9 100644
--- a/src/csharp/Grpc.Core/ChannelOptions.cs
+++ b/src/csharp/Grpc.Core/ChannelOptions.cs
@@ -1,5 +1,5 @@
 #region Copyright notice and license
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -73,8 +73,8 @@ namespace Grpc.Core
         public ChannelOption(string name, string stringValue)
         {
             this.type = OptionType.String;
-            this.name = Preconditions.CheckNotNull(name, "name");
-            this.stringValue = Preconditions.CheckNotNull(stringValue, "stringValue");
+            this.name = GrpcPreconditions.CheckNotNull(name, "name");
+            this.stringValue = GrpcPreconditions.CheckNotNull(stringValue, "stringValue");
         }
 
         /// <summary>
@@ -85,7 +85,7 @@ namespace Grpc.Core
         public ChannelOption(string name, int intValue)
         {
             this.type = OptionType.Integer;
-            this.name = Preconditions.CheckNotNull(name, "name");
+            this.name = GrpcPreconditions.CheckNotNull(name, "name");
             this.intValue = intValue;
         }
 
@@ -118,7 +118,7 @@ namespace Grpc.Core
         {
             get
             {
-                Preconditions.CheckState(type == OptionType.Integer);
+                GrpcPreconditions.CheckState(type == OptionType.Integer);
                 return intValue;
             }
         }
@@ -130,7 +130,7 @@ namespace Grpc.Core
         {
             get
             {
-                Preconditions.CheckState(type == OptionType.String);
+                GrpcPreconditions.CheckState(type == OptionType.String);
                 return stringValue;
             }
         }
diff --git a/src/csharp/Grpc.Core/ContextPropagationToken.cs b/src/csharp/Grpc.Core/ContextPropagationToken.cs
index 1d899b97fd..c0f638f837 100644
--- a/src/csharp/Grpc.Core/ContextPropagationToken.cs
+++ b/src/csharp/Grpc.Core/ContextPropagationToken.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -68,7 +68,7 @@ namespace Grpc.Core
 
         internal ContextPropagationToken(CallSafeHandle parentCall, DateTime deadline, CancellationToken cancellationToken, ContextPropagationOptions options)
         {
-            this.parentCall = Preconditions.CheckNotNull(parentCall);
+            this.parentCall = GrpcPreconditions.CheckNotNull(parentCall);
             this.deadline = deadline;
             this.cancellationToken = cancellationToken;
             this.options = options ?? ContextPropagationOptions.Default;
diff --git a/src/csharp/Grpc.Core/Grpc.Core.csproj b/src/csharp/Grpc.Core/Grpc.Core.csproj
index 9587503e4b..3189835ccd 100644
--- a/src/csharp/Grpc.Core/Grpc.Core.csproj
+++ b/src/csharp/Grpc.Core/Grpc.Core.csproj
@@ -39,8 +39,7 @@
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
-    <Reference Include="System.Interactive.Async, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL">
-      <SpecificVersion>False</SpecificVersion>
+    <Reference Include="System.Interactive.Async">
       <HintPath>..\packages\Ix-Async.1.2.5\lib\net45\System.Interactive.Async.dll</HintPath>
     </Reference>
   </ItemGroup>
@@ -59,6 +58,7 @@
     <Compile Include="IServerStreamWriter.cs" />
     <Compile Include="IAsyncStreamWriter.cs" />
     <Compile Include="IAsyncStreamReader.cs" />
+    <Compile Include="Logging\NullLogger.cs" />
     <Compile Include="ServerPort.cs" />
     <Compile Include="Version.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
@@ -90,7 +90,6 @@
     <Compile Include="Internal\AsyncCallBase.cs" />
     <Compile Include="Internal\AsyncCallServer.cs" />
     <Compile Include="Internal\AsyncCall.cs" />
-    <Compile Include="Utils\Preconditions.cs" />
     <Compile Include="Internal\ServerCredentialsSafeHandle.cs" />
     <Compile Include="ServerCredentials.cs" />
     <Compile Include="Metadata.cs" />
@@ -129,6 +128,7 @@
     <Compile Include="Profiling\IProfiler.cs" />
     <Compile Include="Profiling\Profilers.cs" />
     <Compile Include="Internal\DefaultSslRootsOverride.cs" />
+    <Compile Include="Utils\GrpcPreconditions.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Grpc.Core.nuspec" />
diff --git a/src/csharp/Grpc.Core/GrpcEnvironment.cs b/src/csharp/Grpc.Core/GrpcEnvironment.cs
index f3aa3d79de..86b37b8660 100644
--- a/src/csharp/Grpc.Core/GrpcEnvironment.cs
+++ b/src/csharp/Grpc.Core/GrpcEnvironment.cs
@@ -83,7 +83,7 @@ namespace Grpc.Core
         {
             lock (staticLock)
             {
-                Preconditions.CheckState(refCount > 0);
+                GrpcPreconditions.CheckState(refCount > 0);
                 refCount--;
                 if (refCount == 0)
                 {
@@ -118,7 +118,7 @@ namespace Grpc.Core
         /// </summary>
         public static void SetLogger(ILogger customLogger)
         {
-            Preconditions.CheckNotNull(customLogger, "customLogger");
+            GrpcPreconditions.CheckNotNull(customLogger, "customLogger");
             logger = customLogger;
         }
 
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index 7dc4490281..2caba260b3 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -99,7 +99,7 @@ namespace Grpc.Core.Internal
 
                 lock (myLock)
                 {
-                    Preconditions.CheckState(!started);
+                    GrpcPreconditions.CheckState(!started);
                     started = true;
                     Initialize(cq);
 
@@ -141,7 +141,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckState(!started);
+                GrpcPreconditions.CheckState(!started);
                 started = true;
 
                 Initialize(environment.CompletionQueue);
@@ -168,7 +168,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckState(!started);
+                GrpcPreconditions.CheckState(!started);
                 started = true;
 
                 Initialize(environment.CompletionQueue);
@@ -192,7 +192,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckState(!started);
+                GrpcPreconditions.CheckState(!started);
                 started = true;
 
                 Initialize(environment.CompletionQueue);
@@ -217,7 +217,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckState(!started);
+                GrpcPreconditions.CheckState(!started);
                 started = true;
 
                 Initialize(environment.CompletionQueue);
@@ -257,7 +257,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
+                GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
                 CheckSendingAllowed();
 
                 call.StartSendCloseFromClient(HandleHalfclosed);
@@ -297,7 +297,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckState(finishedStatus.HasValue, "Status can only be accessed once the call has finished.");
+                GrpcPreconditions.CheckState(finishedStatus.HasValue, "Status can only be accessed once the call has finished.");
                 return finishedStatus.Value.Status;
             }
         }
@@ -310,7 +310,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckState(finishedStatus.HasValue, "Trailers can only be accessed once the call has finished.");
+                GrpcPreconditions.CheckState(finishedStatus.HasValue, "Trailers can only be accessed once the call has finished.");
                 return finishedStatus.Value.Trailers;
             }
         }
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
index 81a9a40fcc..45d4c3e078 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
@@ -79,9 +79,9 @@ namespace Grpc.Core.Internal
 
         public AsyncCallBase(Func<TWrite, byte[]> serializer, Func<byte[], TRead> deserializer, GrpcEnvironment environment)
         {
-            this.serializer = Preconditions.CheckNotNull(serializer);
-            this.deserializer = Preconditions.CheckNotNull(deserializer);
-            this.environment = Preconditions.CheckNotNull(environment);
+            this.serializer = GrpcPreconditions.CheckNotNull(serializer);
+            this.deserializer = GrpcPreconditions.CheckNotNull(deserializer);
+            this.environment = GrpcPreconditions.CheckNotNull(environment);
         }
 
         /// <summary>
@@ -91,7 +91,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckState(started);
+                GrpcPreconditions.CheckState(started);
                 cancelRequested = true;
 
                 if (!disposed)
@@ -135,7 +135,7 @@ namespace Grpc.Core.Internal
 
             lock (myLock)
             {
-                Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
+                GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
                 CheckSendingAllowed();
 
                 call.StartSendMessage(HandleSendFinished, payload, writeFlags, !initialMetadataSent);
@@ -154,7 +154,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
+                GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
                 CheckReadingAllowed();
 
                 call.StartReceiveMessage(HandleReadFinished);
@@ -204,22 +204,22 @@ namespace Grpc.Core.Internal
 
         protected void CheckSendingAllowed()
         {
-            Preconditions.CheckState(started);
+            GrpcPreconditions.CheckState(started);
             CheckNotCancelled();
-            Preconditions.CheckState(!disposed);
+            GrpcPreconditions.CheckState(!disposed);
 
-            Preconditions.CheckState(!halfcloseRequested, "Already halfclosed.");
-            Preconditions.CheckState(!finished, "Already finished.");
-            Preconditions.CheckState(sendCompletionDelegate == null, "Only one write can be pending at a time");
+            GrpcPreconditions.CheckState(!halfcloseRequested, "Already halfclosed.");
+            GrpcPreconditions.CheckState(!finished, "Already finished.");
+            GrpcPreconditions.CheckState(sendCompletionDelegate == null, "Only one write can be pending at a time");
         }
 
         protected virtual void CheckReadingAllowed()
         {
-            Preconditions.CheckState(started);
-            Preconditions.CheckState(!disposed);
+            GrpcPreconditions.CheckState(started);
+            GrpcPreconditions.CheckState(!disposed);
 
-            Preconditions.CheckState(!readingDone, "Stream has already been closed.");
-            Preconditions.CheckState(readCompletionDelegate == null, "Only one read can be pending at a time");
+            GrpcPreconditions.CheckState(!readingDone, "Stream has already been closed.");
+            GrpcPreconditions.CheckState(readCompletionDelegate == null, "Only one read can be pending at a time");
         }
 
         protected void CheckNotCancelled()
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
index 6752d3fab3..b72cbd795f 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
@@ -53,7 +53,7 @@ namespace Grpc.Core.Internal
 
         public AsyncCallServer(Func<TResponse, byte[]> serializer, Func<byte[], TRequest> deserializer, GrpcEnvironment environment, Server server) : base(serializer, deserializer, environment)
         {
-            this.server = Preconditions.CheckNotNull(server);
+            this.server = GrpcPreconditions.CheckNotNull(server);
         }
 
         public void Initialize(CallSafeHandle call)
@@ -71,7 +71,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckNotNull(call);
+                GrpcPreconditions.CheckNotNull(call);
 
                 started = true;
 
@@ -108,14 +108,14 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckNotNull(headers, "metadata");
-                Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
+                GrpcPreconditions.CheckNotNull(headers, "metadata");
+                GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
 
-                Preconditions.CheckState(!initialMetadataSent, "Response headers can only be sent once per call.");
-                Preconditions.CheckState(streamingWritesCounter == 0, "Response headers can only be sent before the first write starts.");
+                GrpcPreconditions.CheckState(!initialMetadataSent, "Response headers can only be sent once per call.");
+                GrpcPreconditions.CheckState(streamingWritesCounter == 0, "Response headers can only be sent before the first write starts.");
                 CheckSendingAllowed();
 
-                Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
+                GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
 
                 using (var metadataArray = MetadataArraySafeHandle.Create(headers))
                 {
@@ -136,7 +136,7 @@ namespace Grpc.Core.Internal
         {
             lock (myLock)
             {
-                Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
+                GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
                 CheckSendingAllowed();
 
                 using (var metadataArray = MetadataArraySafeHandle.Create(trailers))
@@ -177,7 +177,7 @@ namespace Grpc.Core.Internal
         protected override void CheckReadingAllowed()
         {
             base.CheckReadingAllowed();
-            Preconditions.CheckArgument(!cancelRequested);
+            GrpcPreconditions.CheckArgument(!cancelRequested);
         }
 
         protected override void OnAfterReleaseResources()
diff --git a/src/csharp/Grpc.Core/Internal/CompletionQueueSafeHandle.cs b/src/csharp/Grpc.Core/Internal/CompletionQueueSafeHandle.cs
index 9d7a990c42..5c75b52e23 100644
--- a/src/csharp/Grpc.Core/Internal/CompletionQueueSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/CompletionQueueSafeHandle.cs
@@ -101,7 +101,7 @@ namespace Grpc.Core.Internal
         {
             bool success = false;
             shutdownRefcount.IncrementIfNonzero(ref success);
-            Preconditions.CheckState(success, "Shutdown has already been called");
+            GrpcPreconditions.CheckState(success, "Shutdown has already been called");
         }
 
         private void EndOp()
diff --git a/src/csharp/Grpc.Core/Internal/CompletionRegistry.cs b/src/csharp/Grpc.Core/Internal/CompletionRegistry.cs
index 2796c959a3..3a293e1626 100644
--- a/src/csharp/Grpc.Core/Internal/CompletionRegistry.cs
+++ b/src/csharp/Grpc.Core/Internal/CompletionRegistry.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -59,7 +59,7 @@ namespace Grpc.Core.Internal
         public void Register(IntPtr key, OpCompletionDelegate callback)
         {
             environment.DebugStats.PendingBatchCompletions.Increment();
-            Preconditions.CheckState(dict.TryAdd(key, callback));
+            GrpcPreconditions.CheckState(dict.TryAdd(key, callback));
         }
 
         public void RegisterBatchCompletion(BatchContextSafeHandle ctx, BatchCompletionDelegate callback)
@@ -71,7 +71,7 @@ namespace Grpc.Core.Internal
         public OpCompletionDelegate Extract(IntPtr key)
         {
             OpCompletionDelegate value;
-            Preconditions.CheckState(dict.TryRemove(key, out value));
+            GrpcPreconditions.CheckState(dict.TryRemove(key, out value));
             environment.DebugStats.PendingBatchCompletions.Decrement();
             return value;
         }
diff --git a/src/csharp/Grpc.Core/Internal/Enums.cs b/src/csharp/Grpc.Core/Internal/Enums.cs
index b0eab2001b..098e7c0e99 100644
--- a/src/csharp/Grpc.Core/Internal/Enums.cs
+++ b/src/csharp/Grpc.Core/Internal/Enums.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -72,7 +72,7 @@ namespace Grpc.Core.Internal
         /// </summary>
         public static void CheckOk(this GRPCCallError callError)
         {
-            Preconditions.CheckState(callError == GRPCCallError.OK, "Call error: " + callError);
+            GrpcPreconditions.CheckState(callError == GRPCCallError.OK, "Call error: " + callError);
         }
     }
 
diff --git a/src/csharp/Grpc.Core/Internal/NativeMetadataCredentialsPlugin.cs b/src/csharp/Grpc.Core/Internal/NativeMetadataCredentialsPlugin.cs
index 36b865c09c..e810ffcdd0 100644
--- a/src/csharp/Grpc.Core/Internal/NativeMetadataCredentialsPlugin.cs
+++ b/src/csharp/Grpc.Core/Internal/NativeMetadataCredentialsPlugin.cs
@@ -53,7 +53,7 @@ namespace Grpc.Core.Internal
 
         public NativeMetadataCredentialsPlugin(AsyncAuthInterceptor interceptor)
         {
-            this.interceptor = Preconditions.CheckNotNull(interceptor, "interceptor");
+            this.interceptor = GrpcPreconditions.CheckNotNull(interceptor, "interceptor");
             this.nativeInterceptor = NativeMetadataInterceptorHandler;
 
             // Make sure the callback doesn't get garbage collected until it is destroyed.
diff --git a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
index de66759b94..ccf144de2d 100644
--- a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -78,10 +78,10 @@ namespace Grpc.Core.Internal
             var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
-                Preconditions.CheckArgument(await requestStream.MoveNext().ConfigureAwait(false));
+                GrpcPreconditions.CheckArgument(await requestStream.MoveNext().ConfigureAwait(false));
                 var request = requestStream.Current;
                 // TODO(jtattermusch): we need to read the full stream so that native callhandle gets deallocated.
-                Preconditions.CheckArgument(!await requestStream.MoveNext().ConfigureAwait(false));
+                GrpcPreconditions.CheckArgument(!await requestStream.MoveNext().ConfigureAwait(false));
                 var result = await handler(request, context).ConfigureAwait(false);
                 status = context.Status;
                 await responseStream.WriteAsync(result).ConfigureAwait(false);
@@ -134,10 +134,10 @@ namespace Grpc.Core.Internal
             var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
-                Preconditions.CheckArgument(await requestStream.MoveNext().ConfigureAwait(false));
+                GrpcPreconditions.CheckArgument(await requestStream.MoveNext().ConfigureAwait(false));
                 var request = requestStream.Current;
                 // TODO(jtattermusch): we need to read the full stream so that native callhandle gets deallocated.
-                Preconditions.CheckArgument(!await requestStream.MoveNext().ConfigureAwait(false));
+                GrpcPreconditions.CheckArgument(!await requestStream.MoveNext().ConfigureAwait(false));
                 await handler(request, responseStream, context).ConfigureAwait(false);
                 status = context.Status;
             }
diff --git a/src/csharp/Grpc.Core/Internal/ServerCredentialsSafeHandle.cs b/src/csharp/Grpc.Core/Internal/ServerCredentialsSafeHandle.cs
index a1d080c7f1..a50f357990 100644
--- a/src/csharp/Grpc.Core/Internal/ServerCredentialsSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerCredentialsSafeHandle.cs
@@ -49,7 +49,7 @@ namespace Grpc.Core.Internal
 
         public static ServerCredentialsSafeHandle CreateSslCredentials(string pemRootCerts, string[] keyCertPairCertChainArray, string[] keyCertPairPrivateKeyArray, bool forceClientAuth)
         {
-            Preconditions.CheckArgument(keyCertPairCertChainArray.Length == keyCertPairPrivateKeyArray.Length);
+            GrpcPreconditions.CheckArgument(keyCertPairCertChainArray.Length == keyCertPairPrivateKeyArray.Length);
             return Native.grpcsharp_ssl_server_credentials_create(pemRootCerts,
                                                                   keyCertPairCertChainArray, keyCertPairPrivateKeyArray,
                                                                   new UIntPtr((ulong)keyCertPairCertChainArray.Length),
diff --git a/src/csharp/Grpc.Core/Internal/Timespec.cs b/src/csharp/Grpc.Core/Internal/Timespec.cs
index 148d877da5..754be4e035 100644
--- a/src/csharp/Grpc.Core/Internal/Timespec.cs
+++ b/src/csharp/Grpc.Core/Internal/Timespec.cs
@@ -141,8 +141,8 @@ namespace Grpc.Core.Internal
         /// </summary>
         public DateTime ToDateTime()
         {
-            Preconditions.CheckState(tv_nsec >= 0 && tv_nsec < NanosPerSecond);
-            Preconditions.CheckState(clock_type == GPRClockType.Realtime);
+            GrpcPreconditions.CheckState(tv_nsec >= 0 && tv_nsec < NanosPerSecond);
+            GrpcPreconditions.CheckState(clock_type == GPRClockType.Realtime);
 
             // fast path for InfFuture
             if (this.Equals(InfFuture))
@@ -195,7 +195,7 @@ namespace Grpc.Core.Internal
                 return Timespec.InfPast;
             }
 
-            Preconditions.CheckArgument(dateTime.Kind == DateTimeKind.Utc, "dateTime needs of kind DateTimeKind.Utc or be equal to DateTime.MaxValue or DateTime.MinValue.");
+            GrpcPreconditions.CheckArgument(dateTime.Kind == DateTimeKind.Utc, "dateTime needs of kind DateTimeKind.Utc or be equal to DateTime.MaxValue or DateTime.MinValue.");
 
             try
             {
diff --git a/src/csharp/Grpc.Core/Internal/UnmanagedLibrary.cs b/src/csharp/Grpc.Core/Internal/UnmanagedLibrary.cs
index 95a8797e3e..e763c15025 100644
--- a/src/csharp/Grpc.Core/Internal/UnmanagedLibrary.cs
+++ b/src/csharp/Grpc.Core/Internal/UnmanagedLibrary.cs
@@ -65,7 +65,7 @@ namespace Grpc.Core.Internal
 
         public UnmanagedLibrary(string libraryPath)
         {
-            this.libraryPath = Preconditions.CheckNotNull(libraryPath);
+            this.libraryPath = GrpcPreconditions.CheckNotNull(libraryPath);
 
             if (!File.Exists(this.libraryPath))
             {
diff --git a/src/csharp/Grpc.Core/KeyCertificatePair.cs b/src/csharp/Grpc.Core/KeyCertificatePair.cs
index 6f691975e9..0fb6817986 100644
--- a/src/csharp/Grpc.Core/KeyCertificatePair.cs
+++ b/src/csharp/Grpc.Core/KeyCertificatePair.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -54,8 +54,8 @@ namespace Grpc.Core
         /// <param name="privateKey">PEM encoded private key.</param>
         public KeyCertificatePair(string certificateChain, string privateKey)
         {
-            this.certificateChain = Preconditions.CheckNotNull(certificateChain, "certificateChain");
-            this.privateKey = Preconditions.CheckNotNull(privateKey, "privateKey");
+            this.certificateChain = GrpcPreconditions.CheckNotNull(certificateChain, "certificateChain");
+            this.privateKey = GrpcPreconditions.CheckNotNull(privateKey, "privateKey");
         }
 
         /// <summary>
diff --git a/src/csharp/Grpc.Core/Logging/NullLogger.cs b/src/csharp/Grpc.Core/Logging/NullLogger.cs
new file mode 100644
index 0000000000..58679a0ff9
--- /dev/null
+++ b/src/csharp/Grpc.Core/Logging/NullLogger.cs
@@ -0,0 +1,122 @@
+#region Copyright notice and license
+
+// Copyright 2016, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+
+namespace Grpc.Core.Logging
+{
+    /// <summary>
+    /// Logger which doesn't log any information anywhere.
+    /// </summary>
+    public sealed class NullLogger : ILogger
+    {
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Debug(string message)
+        {
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Debug(string format, params object[] formatArgs)
+        {
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Error(string message)
+        {
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Error(Exception exception, string message)
+        {
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Error(string format, params object[] formatArgs)
+        {
+        }
+
+        /// <summary>
+        /// Returns a reference to the instance on which the method is called, as
+        /// instances aren't associated with specific types.
+        /// </summary>
+        public ILogger ForType<T>()
+        {
+            return this;
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Info(string message)
+        {
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Info(string format, params object[] formatArgs)
+        {
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Warning(string message)
+        {
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Warning(Exception exception, string message)
+        {
+        }
+
+        /// <summary>
+        /// As with all logging calls on this logger, this method is a no-op.
+        /// </summary>
+        public void Warning(string format, params object[] formatArgs)
+        {
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core/Marshaller.cs b/src/csharp/Grpc.Core/Marshaller.cs
index 3493d2d38f..5847248c1a 100644
--- a/src/csharp/Grpc.Core/Marshaller.cs
+++ b/src/csharp/Grpc.Core/Marshaller.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -51,8 +51,8 @@ namespace Grpc.Core
         /// <param name="deserializer">Function that will be used to deserialize messages.</param>
         public Marshaller(Func<T, byte[]> serializer, Func<byte[], T> deserializer)
         {
-            this.serializer = Preconditions.CheckNotNull(serializer, "serializer");
-            this.deserializer = Preconditions.CheckNotNull(deserializer, "deserializer");
+            this.serializer = GrpcPreconditions.CheckNotNull(serializer, "serializer");
+            this.deserializer = GrpcPreconditions.CheckNotNull(deserializer, "deserializer");
         }
 
         /// <summary>
diff --git a/src/csharp/Grpc.Core/Metadata.cs b/src/csharp/Grpc.Core/Metadata.cs
index 21bdf4f114..aa22f840d6 100644
--- a/src/csharp/Grpc.Core/Metadata.cs
+++ b/src/csharp/Grpc.Core/Metadata.cs
@@ -1,5 +1,5 @@
 #region Copyright notice and license
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -179,7 +179,7 @@ namespace Grpc.Core
 
         private void CheckWriteable()
         {
-            Preconditions.CheckState(!readOnly, "Object is read only");
+            GrpcPreconditions.CheckState(!readOnly, "Object is read only");
         }
 
         #endregion
@@ -211,10 +211,10 @@ namespace Grpc.Core
             public Entry(string key, byte[] valueBytes)
             {
                 this.key = NormalizeKey(key);
-                Preconditions.CheckArgument(this.key.EndsWith(BinaryHeaderSuffix),
+                GrpcPreconditions.CheckArgument(this.key.EndsWith(BinaryHeaderSuffix),
                     "Key for binary valued metadata entry needs to have suffix indicating binary value.");
                 this.value = null;
-                Preconditions.CheckNotNull(valueBytes, "valueBytes");
+                GrpcPreconditions.CheckNotNull(valueBytes, "valueBytes");
                 this.valueBytes = new byte[valueBytes.Length];
                 Buffer.BlockCopy(valueBytes, 0, this.valueBytes, 0, valueBytes.Length);  // defensive copy to guarantee immutability
             }
@@ -227,9 +227,9 @@ namespace Grpc.Core
             public Entry(string key, string value)
             {
                 this.key = NormalizeKey(key);
-                Preconditions.CheckArgument(!this.key.EndsWith(BinaryHeaderSuffix),
+                GrpcPreconditions.CheckArgument(!this.key.EndsWith(BinaryHeaderSuffix),
                     "Key for ASCII valued metadata entry cannot have suffix indicating binary value.");
-                this.value = Preconditions.CheckNotNull(value, "value");
+                this.value = GrpcPreconditions.CheckNotNull(value, "value");
                 this.valueBytes = null;
             }
 
@@ -270,7 +270,7 @@ namespace Grpc.Core
             {
                 get
                 {
-                    Preconditions.CheckState(!IsBinary, "Cannot access string value of a binary metadata entry");
+                    GrpcPreconditions.CheckState(!IsBinary, "Cannot access string value of a binary metadata entry");
                     return value ?? Encoding.GetString(valueBytes);
                 }
             }
@@ -323,8 +323,8 @@ namespace Grpc.Core
 
             private static string NormalizeKey(string key)
             {
-                var normalized = Preconditions.CheckNotNull(key, "key").ToLower(CultureInfo.InvariantCulture);
-                Preconditions.CheckArgument(ValidKeyRegex.IsMatch(normalized), 
+                var normalized = GrpcPreconditions.CheckNotNull(key, "key").ToLower(CultureInfo.InvariantCulture);
+                GrpcPreconditions.CheckArgument(ValidKeyRegex.IsMatch(normalized), 
                     "Metadata entry key not valid. Keys can only contain lowercase alphanumeric characters, underscores and hyphens.");
                 return normalized;
             }
diff --git a/src/csharp/Grpc.Core/Method.cs b/src/csharp/Grpc.Core/Method.cs
index 99162a7d5d..3870076f7f 100644
--- a/src/csharp/Grpc.Core/Method.cs
+++ b/src/csharp/Grpc.Core/Method.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -106,10 +106,10 @@ namespace Grpc.Core
         public Method(MethodType type, string serviceName, string name, Marshaller<TRequest> requestMarshaller, Marshaller<TResponse> responseMarshaller)
         {
             this.type = type;
-            this.serviceName = Preconditions.CheckNotNull(serviceName, "serviceName");
-            this.name = Preconditions.CheckNotNull(name, "name");
-            this.requestMarshaller = Preconditions.CheckNotNull(requestMarshaller, "requestMarshaller");
-            this.responseMarshaller = Preconditions.CheckNotNull(responseMarshaller, "responseMarshaller");
+            this.serviceName = GrpcPreconditions.CheckNotNull(serviceName, "serviceName");
+            this.name = GrpcPreconditions.CheckNotNull(name, "name");
+            this.requestMarshaller = GrpcPreconditions.CheckNotNull(requestMarshaller, "requestMarshaller");
+            this.responseMarshaller = GrpcPreconditions.CheckNotNull(responseMarshaller, "responseMarshaller");
             this.fullName = GetFullName(serviceName, name);
         }
 
diff --git a/src/csharp/Grpc.Core/Profiling/Profilers.cs b/src/csharp/Grpc.Core/Profiling/Profilers.cs
index 471ee20875..8a181447d6 100644
--- a/src/csharp/Grpc.Core/Profiling/Profilers.cs
+++ b/src/csharp/Grpc.Core/Profiling/Profilers.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -111,7 +111,7 @@ namespace Grpc.Core.Profiling
 
         public void Dump(string filepath)
         {
-            using (var stream = new StreamWriter(filepath))
+            using (var stream = File.CreateText(filepath))
             {
                 Dump(stream);
             }
diff --git a/src/csharp/Grpc.Core/Server.cs b/src/csharp/Grpc.Core/Server.cs
index d120f95fdf..5d0fc6b1f0 100644
--- a/src/csharp/Grpc.Core/Server.cs
+++ b/src/csharp/Grpc.Core/Server.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -125,7 +125,7 @@ namespace Grpc.Core
         {
             lock (myLock)
             {
-                Preconditions.CheckState(!startRequested);
+                GrpcPreconditions.CheckState(!startRequested);
                 startRequested = true;
                 
                 handle.Start();
@@ -142,8 +142,8 @@ namespace Grpc.Core
         {
             lock (myLock)
             {
-                Preconditions.CheckState(startRequested);
-                Preconditions.CheckState(!shutdownRequested);
+                GrpcPreconditions.CheckState(startRequested);
+                GrpcPreconditions.CheckState(!shutdownRequested);
                 shutdownRequested = true;
             }
 
@@ -162,8 +162,8 @@ namespace Grpc.Core
         {
             lock (myLock)
             {
-                Preconditions.CheckState(startRequested);
-                Preconditions.CheckState(!shutdownRequested);
+                GrpcPreconditions.CheckState(startRequested);
+                GrpcPreconditions.CheckState(!shutdownRequested);
                 shutdownRequested = true;
             }
 
@@ -181,7 +181,7 @@ namespace Grpc.Core
 
             bool success = false;
             handle.DangerousAddRef(ref success);
-            Preconditions.CheckState(success);
+            GrpcPreconditions.CheckState(success);
         }
 
         internal void RemoveCallReference(object call)
@@ -197,7 +197,7 @@ namespace Grpc.Core
         {
             lock (myLock)
             {
-                Preconditions.CheckState(!startRequested);
+                GrpcPreconditions.CheckState(!startRequested);
                 foreach (var entry in serviceDefinition.CallHandlers)
                 {
                     callHandlers.Add(entry.Key, entry.Value);
@@ -213,8 +213,8 @@ namespace Grpc.Core
         {
             lock (myLock)
             {
-                Preconditions.CheckNotNull(serverPort.Credentials, "serverPort");
-                Preconditions.CheckState(!startRequested);
+                GrpcPreconditions.CheckNotNull(serverPort.Credentials, "serverPort");
+                GrpcPreconditions.CheckState(!startRequested);
                 var address = string.Format("{0}:{1}", serverPort.Host, serverPort.Port);
                 int boundPort;
                 using (var nativeCredentials = serverPort.Credentials.ToNativeCredentials())
diff --git a/src/csharp/Grpc.Core/ServerCredentials.cs b/src/csharp/Grpc.Core/ServerCredentials.cs
index 3c6703d30e..456d331c9c 100644
--- a/src/csharp/Grpc.Core/ServerCredentials.cs
+++ b/src/csharp/Grpc.Core/ServerCredentials.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -90,11 +90,11 @@ namespace Grpc.Core
         public SslServerCredentials(IEnumerable<KeyCertificatePair> keyCertificatePairs, string rootCertificates, bool forceClientAuth)
         {
             this.keyCertificatePairs = new List<KeyCertificatePair>(keyCertificatePairs).AsReadOnly();
-            Preconditions.CheckArgument(this.keyCertificatePairs.Count > 0,
+            GrpcPreconditions.CheckArgument(this.keyCertificatePairs.Count > 0,
                 "At least one KeyCertificatePair needs to be provided.");
             if (forceClientAuth)
             {
-                Preconditions.CheckNotNull(rootCertificates,
+                GrpcPreconditions.CheckNotNull(rootCertificates,
                     "Cannot force client authentication unless you provide rootCertificates.");
             }
             this.rootCertificates = rootCertificates;
diff --git a/src/csharp/Grpc.Core/ServerPort.cs b/src/csharp/Grpc.Core/ServerPort.cs
index 598404d045..10ddcb782f 100644
--- a/src/csharp/Grpc.Core/ServerPort.cs
+++ b/src/csharp/Grpc.Core/ServerPort.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -62,9 +62,9 @@ namespace Grpc.Core
         /// <param name="credentials">credentials to use to secure this port.</param>
         public ServerPort(string host, int port, ServerCredentials credentials)
         {
-            this.host = Preconditions.CheckNotNull(host, "host");
+            this.host = GrpcPreconditions.CheckNotNull(host, "host");
             this.port = port;
-            this.credentials = Preconditions.CheckNotNull(credentials, "credentials");
+            this.credentials = GrpcPreconditions.CheckNotNull(credentials, "credentials");
         }
 
         /// <summary>
diff --git a/src/csharp/Grpc.Core/Utils/Preconditions.cs b/src/csharp/Grpc.Core/Utils/GrpcPreconditions.cs
index a8ab603391..76bf04ce8b 100644
--- a/src/csharp/Grpc.Core/Utils/Preconditions.cs
+++ b/src/csharp/Grpc.Core/Utils/GrpcPreconditions.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -38,7 +38,7 @@ namespace Grpc.Core.Utils
     /// <summary>
     /// Utility methods to simplify checking preconditions in the code.
     /// </summary>
-    public static class Preconditions
+    public static class GrpcPreconditions
     {
         /// <summary>
         /// Throws <see cref="ArgumentException"/> if condition is false.
diff --git a/src/csharp/Grpc.Core/VersionInfo.cs b/src/csharp/Grpc.Core/VersionInfo.cs
index 04741ae835..4bd4f204dd 100644
--- a/src/csharp/Grpc.Core/VersionInfo.cs
+++ b/src/csharp/Grpc.Core/VersionInfo.cs
@@ -41,11 +41,11 @@ namespace Grpc.Core
         /// <summary>
         /// Current version of gRPC C# assemblies
         /// </summary>
-        public const string CurrentAssemblyVersion = "0.13.1.0";
+        public const string CurrentAssemblyVersion = "0.14.0.0";
 
         /// <summary>
         /// Current version of gRPC C#
         /// </summary>
-        public const string CurrentVersion = "0.13.1-pre1";
+        public const string CurrentVersion = "0.14.0-dev";
     }
 }
diff --git a/src/csharp/Grpc.HealthCheck/HealthServiceImpl.cs b/src/csharp/Grpc.HealthCheck/HealthServiceImpl.cs
index 26c6445c35..e2ad1a834b 100644
--- a/src/csharp/Grpc.HealthCheck/HealthServiceImpl.cs
+++ b/src/csharp/Grpc.HealthCheck/HealthServiceImpl.cs
@@ -1,5 +1,5 @@
 #region Copyright notice and license
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -127,8 +127,8 @@ namespace Grpc.HealthCheck
         {
             public Key(string host, string service)
             {
-                this.Host = Preconditions.CheckNotNull(host);
-                this.Service = Preconditions.CheckNotNull(service);
+                this.Host = GrpcPreconditions.CheckNotNull(host);
+                this.Service = GrpcPreconditions.CheckNotNull(service);
             }
 
             readonly string Host;
diff --git a/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs b/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
index e9e659cb1f..c4016012cb 100644
--- a/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
+++ b/src/csharp/Grpc.IntegrationTesting/ClientRunners.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -58,7 +58,7 @@ namespace Grpc.IntegrationTesting
         public static IClientRunner CreateStarted(ClientConfig config)
         {
             string target = config.ServerTargets.Single();
-            Grpc.Core.Utils.Preconditions.CheckArgument(config.LoadParams.LoadCase == LoadParams.LoadOneofCase.ClosedLoop);
+            GrpcPreconditions.CheckArgument(config.LoadParams.LoadCase == LoadParams.LoadOneofCase.ClosedLoop);
 
             var credentials = config.SecurityParams != null ? TestCredentials.CreateSslCredentials() : ChannelCredentials.Insecure;
             var channel = new Channel(target, credentials);
@@ -95,7 +95,7 @@ namespace Grpc.IntegrationTesting
         
         public SyncUnaryClientRunner(Channel channel, int payloadSize, HistogramParams histogramParams)
         {
-            this.channel = Grpc.Core.Utils.Preconditions.CheckNotNull(channel);
+            this.channel = GrpcPreconditions.CheckNotNull(channel);
             this.payloadSize = payloadSize;
             this.histogram = new Histogram(histogramParams.Resolution, histogramParams.MaxPossible);
 
diff --git a/src/csharp/Grpc.IntegrationTesting/Histogram.cs b/src/csharp/Grpc.IntegrationTesting/Histogram.cs
index 7e7cb2c4de..08a674d817 100644
--- a/src/csharp/Grpc.IntegrationTesting/Histogram.cs
+++ b/src/csharp/Grpc.IntegrationTesting/Histogram.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -66,8 +66,8 @@ namespace Grpc.IntegrationTesting
 
         public Histogram(double resolution, double maxPossible)
         {
-            Grpc.Core.Utils.Preconditions.CheckArgument(resolution > 0);
-            Grpc.Core.Utils.Preconditions.CheckArgument(maxPossible > 0);
+            GrpcPreconditions.CheckArgument(resolution > 0);
+            GrpcPreconditions.CheckArgument(maxPossible > 0);
             this.maxPossible = maxPossible;
             this.multiplier = 1.0 + resolution;
             this.oneOnLogMultiplier = 1.0 / Math.Log(1.0 + resolution);
diff --git a/src/csharp/Grpc.IntegrationTesting/ServerRunners.cs b/src/csharp/Grpc.IntegrationTesting/ServerRunners.cs
index e8be7758ce..9b09b9bdd3 100644
--- a/src/csharp/Grpc.IntegrationTesting/ServerRunners.cs
+++ b/src/csharp/Grpc.IntegrationTesting/ServerRunners.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -57,7 +57,7 @@ namespace Grpc.IntegrationTesting
         /// </summary>
         public static IServerRunner CreateStarted(ServerConfig config)
         {
-            Grpc.Core.Utils.Preconditions.CheckArgument(config.ServerType == ServerType.ASYNC_SERVER);
+            GrpcPreconditions.CheckArgument(config.ServerType == ServerType.ASYNC_SERVER);
             var credentials = config.SecurityParams != null ? TestCredentials.CreateSslServerCredentials() : ServerCredentials.Insecure;
 
             // TODO: qps_driver needs to setup payload properly...
@@ -83,7 +83,7 @@ namespace Grpc.IntegrationTesting
 
         public ServerRunnerImpl(Server server)
         {
-            this.server = Grpc.Core.Utils.Preconditions.CheckNotNull(server);
+            this.server = GrpcPreconditions.CheckNotNull(server);
         }
 
         public int BoundPort
diff --git a/src/csharp/Grpc.IntegrationTesting/WorkerServiceImpl.cs b/src/csharp/Grpc.IntegrationTesting/WorkerServiceImpl.cs
index bb2918bf46..59ecebf5a2 100644
--- a/src/csharp/Grpc.IntegrationTesting/WorkerServiceImpl.cs
+++ b/src/csharp/Grpc.IntegrationTesting/WorkerServiceImpl.cs
@@ -1,6 +1,6 @@
 #region Copyright notice and license
 
-// Copyright 2015, Google Inc.
+// Copyright 2015-2016, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
@@ -49,7 +49,7 @@ namespace Grpc.Testing
     {
         public async Task RunServer(IAsyncStreamReader<ServerArgs> requestStream, IServerStreamWriter<ServerStatus> responseStream, ServerCallContext context)
         {
-            Grpc.Core.Utils.Preconditions.CheckState(await requestStream.MoveNext());
+            GrpcPreconditions.CheckState(await requestStream.MoveNext());
             var serverConfig = requestStream.Current.Setup;
             var runner = ServerRunners.CreateStarted(serverConfig);
 
@@ -73,7 +73,7 @@ namespace Grpc.Testing
 
         public async Task RunClient(IAsyncStreamReader<ClientArgs> requestStream, IServerStreamWriter<ClientStatus> responseStream, ServerCallContext context)
         {
-            Grpc.Core.Utils.Preconditions.CheckState(await requestStream.MoveNext());
+            GrpcPreconditions.CheckState(await requestStream.MoveNext());
             var clientConfig = requestStream.Current.Setup;
             var runner = ClientRunners.CreateStarted(clientConfig);
 
diff --git a/src/csharp/build_packages.bat b/src/csharp/build_packages.bat
index 7cf962bdc2..b7768f7821 100644
--- a/src/csharp/build_packages.bat
+++ b/src/csharp/build_packages.bat
@@ -1,7 +1,7 @@
 @rem Builds gRPC NuGet packages
 
 @rem Current package versions
-set VERSION=0.13.1-pre1
+set VERSION=0.14.0-dev
 set PROTOBUF_VERSION=3.0.0-beta2
 
 @rem Packages that depend on prerelease packages (like Google.Protobuf) need to have prerelease suffix as well.
diff --git a/src/node/ext/byte_buffer.cc b/src/node/ext/byte_buffer.cc
index ee703fdc91..0f7edada14 100644
--- a/src/node/ext/byte_buffer.cc
+++ b/src/node/ext/byte_buffer.cc
@@ -63,6 +63,10 @@ grpc_byte_buffer *BufferToByteBuffer(Local<Value> buffer) {
   return byte_buffer;
 }
 
+namespace {
+void delete_buffer(char *data, void *hint) { delete[] data; }
+}
+
 Local<Value> ByteBufferToBuffer(grpc_byte_buffer *buffer) {
   Nan::EscapableHandleScope scope;
   if (buffer == NULL) {
@@ -80,7 +84,7 @@ Local<Value> ByteBufferToBuffer(grpc_byte_buffer *buffer) {
     gpr_slice_unref(next);
   }
   return scope.Escape(MakeFastBuffer(
-      Nan::NewBuffer(result, length).ToLocalChecked()));
+      Nan::NewBuffer(result, length, delete_buffer, NULL).ToLocalChecked()));
 }
 
 Local<Value> MakeFastBuffer(Local<Value> slowBuffer) {
diff --git a/src/node/ext/call_credentials.cc b/src/node/ext/call_credentials.cc
index 91acb86254..98696db232 100644
--- a/src/node/ext/call_credentials.cc
+++ b/src/node/ext/call_credentials.cc
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -187,7 +187,8 @@ NAN_METHOD(PluginCallback) {
   shared_ptr<Resources> resources(new Resources);
   grpc_status_code code = static_cast<grpc_status_code>(
       Nan::To<uint32_t>(info[0]).FromJust());
-  char *details = *Utf8String(info[1]);
+  Utf8String details_utf8_str(info[1]);
+  char *details = *details_utf8_str;
   grpc_metadata_array array;
   if (!CreateMetadataArray(Nan::To<Object>(info[2]).ToLocalChecked(),
                            &array, resources)){
diff --git a/src/node/ext/node_grpc.cc b/src/node/ext/node_grpc.cc
index 654c5aed09..0c71b2d610 100644
--- a/src/node/ext/node_grpc.cc
+++ b/src/node/ext/node_grpc.cc
@@ -237,7 +237,8 @@ NAN_METHOD(MetadataKeyIsLegal) {
         "headerKeyIsLegal's argument must be a string");
   }
   Local<String> key = Nan::To<String>(info[0]).ToLocalChecked();
-  char *key_str = *Nan::Utf8String(key);
+  Nan::Utf8String key_utf8_str(key);
+  char *key_str = *key_utf8_str;
   info.GetReturnValue().Set(static_cast<bool>(
       grpc_header_key_is_legal(key_str, static_cast<size_t>(key->Length()))));
 }
@@ -248,7 +249,8 @@ NAN_METHOD(MetadataNonbinValueIsLegal) {
         "metadataNonbinValueIsLegal's argument must be a string");
   }
   Local<String> value = Nan::To<String>(info[0]).ToLocalChecked();
-  char *value_str = *Nan::Utf8String(value);
+  Nan::Utf8String value_utf8_str(value);
+  char *value_str = *value_utf8_str;
   info.GetReturnValue().Set(static_cast<bool>(
       grpc_header_nonbin_value_is_legal(
           value_str, static_cast<size_t>(value->Length()))));
@@ -260,7 +262,8 @@ NAN_METHOD(MetadataKeyIsBinary) {
         "metadataKeyIsLegal's argument must be a string");
   }
   Local<String> key = Nan::To<String>(info[0]).ToLocalChecked();
-  char *key_str = *Nan::Utf8String(key);
+  Nan::Utf8String key_utf8_str(key);
+  char *key_str = *key_utf8_str;
   info.GetReturnValue().Set(static_cast<bool>(
       grpc_is_binary_header(key_str, static_cast<size_t>(key->Length()))));
 }
diff --git a/src/node/index.js b/src/node/index.js
index 7eacdc67b1..1c197729d7 100644
--- a/src/node/index.js
+++ b/src/node/index.js
@@ -56,17 +56,18 @@ var grpc = require('./src/grpc_extension');
 /**
  * Load a gRPC object from an existing ProtoBuf.Reflect object.
  * @param {ProtoBuf.Reflect.Namespace} value The ProtoBuf object to load.
+ * @param {Object=} options Options to apply to the loaded object
  * @return {Object<string, *>} The resulting gRPC object
  */
-exports.loadObject = function loadObject(value) {
+exports.loadObject = function loadObject(value, options) {
   var result = {};
   if (value.className === 'Namespace') {
     _.each(value.children, function(child) {
-      result[child.name] = loadObject(child);
+      result[child.name] = loadObject(child, options);
     });
     return result;
   } else if (value.className === 'Service') {
-    return client.makeProtobufClientConstructor(value);
+    return client.makeProtobufClientConstructor(value, options);
   } else if (value.className === 'Message' || value.className === 'Enum') {
     return value.build();
   } else {
@@ -77,28 +78,45 @@ exports.loadObject = function loadObject(value) {
 var loadObject = exports.loadObject;
 
 /**
- * Load a gRPC object from a .proto file.
- * @param {string} filename The file to load
+ * Load a gRPC object from a .proto file. The options object can provide the
+ * following options:
+ * - convertFieldsToCamelCase: Loads this file with that option on protobuf.js
+ *   set as specified. See
+ *   https://github.com/dcodeIO/protobuf.js/wiki/Advanced-options for details
+ * - binaryAsBase64: deserialize bytes values as base64 strings instead of
+ *   Buffers. Defaults to false
+ * - longsAsStrings: deserialize long values as strings instead of objects.
+ *   Defaults to true
+ * @param {string|{root: string, file: string}} filename The file to load
  * @param {string=} format The file format to expect. Must be either 'proto' or
  *     'json'. Defaults to 'proto'
+ * @param {Object=} options Options to apply to the loaded file
  * @return {Object<string, *>} The resulting gRPC object
  */
-exports.load = function load(filename, format) {
+exports.load = function load(filename, format, options) {
   if (!format) {
     format = 'proto';
   }
+  var convertFieldsToCamelCaseOriginal = ProtoBuf.convertFieldsToCamelCase;
+  if(options && options.hasOwnProperty('convertFieldsToCamelCase')) {
+    ProtoBuf.convertFieldsToCamelCase = options.convertFieldsToCamelCase;
+  }
   var builder;
-  switch(format) {
-    case 'proto':
-    builder = ProtoBuf.loadProtoFile(filename);
-    break;
-    case 'json':
-    builder = ProtoBuf.loadJsonFile(filename);
-    break;
-    default:
-    throw new Error('Unrecognized format "' + format + '"');
+  try {
+    switch(format) {
+      case 'proto':
+      builder = ProtoBuf.loadProtoFile(filename);
+      break;
+      case 'json':
+      builder = ProtoBuf.loadJsonFile(filename);
+      break;
+      default:
+      throw new Error('Unrecognized format "' + format + '"');
+    }
+  } finally {
+    ProtoBuf.convertFieldsToCamelCase = convertFieldsToCamelCaseOriginal;
   }
-  return loadObject(builder.ns);
+  return loadObject(builder.ns, options);
 };
 
 /**
diff --git a/src/node/performance/worker_server.js b/src/node/performance/worker.js
index 7c8ab00026..7c8ab00026 100644
--- a/src/node/performance/worker_server.js
+++ b/src/node/performance/worker.js
diff --git a/src/node/src/client.js b/src/node/src/client.js
index b5247a69ee..c65dd73650 100644
--- a/src/node/src/client.js
+++ b/src/node/src/client.js
@@ -648,8 +648,8 @@ exports.makeClientConstructor = function(methods, serviceName) {
     var deserialize = attrs.responseDeserialize;
     Client.prototype[name] = requester_makers[method_type](
         attrs.path, serialize, deserialize);
-    Client.prototype[name].serialize = serialize;
-    Client.prototype[name].deserialize = deserialize;
+    // Associate all provided attributes with the method
+    _.assign(Client.prototype[name], attrs);
   });
 
   return Client;
@@ -698,13 +698,16 @@ exports.waitForClientReady = function(client, deadline, callback) {
  * Creates a constructor for clients for the given service
  * @param {ProtoBuf.Reflect.Service} service The service to generate a client
  *     for
+ * @param {Object=} options Options to apply to the client
  * @return {function(string, Object)} New client constructor
  */
-exports.makeProtobufClientConstructor =  function(service) {
-  var method_attrs = common.getProtobufServiceAttrs(service, service.name);
+exports.makeProtobufClientConstructor =  function(service, options) {
+  var method_attrs = common.getProtobufServiceAttrs(service, service.name,
+                                                    options);
   var Client = exports.makeClientConstructor(
       method_attrs, common.fullyQualifiedName(service));
   Client.service = service;
+  Client.service.grpc_options = options;
   return Client;
 };
 
diff --git a/src/node/src/common.js b/src/node/src/common.js
index 2e6c01c4d7..7705a275fc 100644
--- a/src/node/src/common.js
+++ b/src/node/src/common.js
@@ -44,9 +44,20 @@ var _ = require('lodash');
 /**
  * Get a function that deserializes a specific type of protobuf.
  * @param {function()} cls The constructor of the message type to deserialize
+ * @param {bool=} binaryAsBase64 Deserialize bytes fields as base64 strings
+ *     instead of Buffers. Defaults to false
+ * @param {bool=} longsAsStrings Deserialize long values as strings instead of
+ *     objects. Defaults to true
  * @return {function(Buffer):cls} The deserialization function
  */
-exports.deserializeCls = function deserializeCls(cls) {
+exports.deserializeCls = function deserializeCls(cls, binaryAsBase64,
+                                                 longsAsStrings) {
+  if (binaryAsBase64 === undefined || binaryAsBase64 === null) {
+    binaryAsBase64 = false;
+  }
+  if (longsAsStrings === undefined || longsAsStrings === null) {
+    longsAsStrings = true;
+  }
   /**
    * Deserialize a buffer to a message object
    * @param {Buffer} arg_buf The buffer to deserialize
@@ -55,7 +66,7 @@ exports.deserializeCls = function deserializeCls(cls) {
   return function deserialize(arg_buf) {
     // Convert to a native object with binary fields as Buffers (first argument)
     // and longs as strings (second argument)
-    return cls.decode(arg_buf).toRaw(false, true);
+    return cls.decode(arg_buf).toRaw(binaryAsBase64, longsAsStrings);
   };
 };
 
@@ -119,19 +130,30 @@ exports.wrapIgnoreNull = function wrapIgnoreNull(func) {
 /**
  * Return a map from method names to method attributes for the service.
  * @param {ProtoBuf.Reflect.Service} service The service to get attributes for
+ * @param {Object=} options Options to apply to these attributes
  * @return {Object} The attributes map
  */
-exports.getProtobufServiceAttrs = function getProtobufServiceAttrs(service) {
+exports.getProtobufServiceAttrs = function getProtobufServiceAttrs(service,
+                                                                   options) {
   var prefix = '/' + fullyQualifiedName(service) + '/';
+  var binaryAsBase64, longsAsStrings;
+  if (options) {
+    binaryAsBase64 = options.binaryAsBase64;
+    longsAsStrings = options.longsAsStrings;
+  }
   return _.object(_.map(service.children, function(method) {
     return [_.camelCase(method.name), {
       path: prefix + method.name,
       requestStream: method.requestStream,
       responseStream: method.responseStream,
+      requestType: method.resolvedRequestType,
+      responseType: method.resolvedResponseType,
       requestSerialize: serializeCls(method.resolvedRequestType.build()),
-      requestDeserialize: deserializeCls(method.resolvedRequestType.build()),
+      requestDeserialize: deserializeCls(method.resolvedRequestType.build(),
+                                     binaryAsBase64, longsAsStrings),
       responseSerialize: serializeCls(method.resolvedResponseType.build()),
-      responseDeserialize: deserializeCls(method.resolvedResponseType.build())
+      responseDeserialize: deserializeCls(method.resolvedResponseType.build(),
+                                     binaryAsBase64, longsAsStrings)
     }];
   }));
 };
diff --git a/src/node/src/credentials.js b/src/node/src/credentials.js
index 710ab6d879..1d73723cc0 100644
--- a/src/node/src/credentials.js
+++ b/src/node/src/credentials.js
@@ -98,6 +98,8 @@ exports.createFromMetadataGenerator = function(metadata_generator) {
         message = error.message;
         if (error.hasOwnProperty('code')) {
           code = error.code;
+        } else {
+          code = grpc.status.UNAUTHENTICATED;
         }
         if (!metadata) {
           metadata = new Metadata();
@@ -116,13 +118,16 @@ exports.createFromMetadataGenerator = function(metadata_generator) {
 exports.createFromGoogleCredential = function(google_credential) {
   return exports.createFromMetadataGenerator(function(auth_context, callback) {
     var service_url = auth_context.service_url;
+    console.log('Service URL:', service_url);
     google_credential.getRequestMetadata(service_url, function(err, header) {
       if (err) {
+        console.log('Auth error:', err);
         callback(err);
         return;
       }
       var metadata = new Metadata();
       metadata.add('authorization', header.Authorization);
+      console.log(header.Authorization);
       callback(null, metadata);
     });
   });
diff --git a/src/node/src/metadata.js b/src/node/src/metadata.js
index 51a9f8a216..33d7ea1cf7 100644
--- a/src/node/src/metadata.js
+++ b/src/node/src/metadata.js
@@ -64,7 +64,7 @@ function normalizeKey(key) {
   if (grpc.metadataKeyIsLegal(key)) {
     return key;
   } else {
-    throw new Error('Metadata key contains illegal characters');
+    throw new Error('Metadata key"' + key + '" contains illegal characters');
   }
 }
 
@@ -79,7 +79,8 @@ function validate(key, value) {
           'keys that don\'t end with \'-bin\' must have String values');
     }
     if (!grpc.metadataNonbinValueIsLegal(value)) {
-      throw new Error('Metadata string value contains illegal characters');
+      throw new Error('Metadata string value "' + value +
+                      '" contains illegal characters');
     }
   }
 }
diff --git a/src/node/src/server.js b/src/node/src/server.js
index e5aadcd565..0cf7ba3424 100644
--- a/src/node/src/server.js
+++ b/src/node/src/server.js
@@ -737,7 +737,12 @@ Server.prototype.addService = function(service, implementation) {
  *     method implementation for the provided service.
  */
 Server.prototype.addProtoService = function(service, implementation) {
-  this.addService(common.getProtobufServiceAttrs(service), implementation);
+  var options;
+  if (service.grpc_options) {
+    options = service.grpc_options;
+  }
+  this.addService(common.getProtobufServiceAttrs(service, options),
+                  implementation);
 };
 
 /**
diff --git a/src/node/test/common_test.js b/src/node/test/common_test.js
index 08ba429ed7..66a4205f82 100644
--- a/src/node/test/common_test.js
+++ b/src/node/test/common_test.js
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -42,7 +42,7 @@ var ProtoBuf = require('protobufjs');
 var messages_proto = ProtoBuf.loadProtoFile(
     __dirname + '/test_messages.proto').build();
 
-describe('Proto message serialize and deserialize', function() {
+describe('Proto message long int serialize and deserialize', function() {
   var longSerialize = common.serializeCls(messages_proto.LongValues);
   var longDeserialize = common.deserializeCls(messages_proto.LongValues);
   var pos_value = '314159265358979';
@@ -87,4 +87,52 @@ describe('Proto message serialize and deserialize', function() {
     assert.strictEqual(longDeserialize(serialized).sfixed_64.toString(),
                        neg_value);
   });
+  it('should deserialize as a number with the right option set', function() {
+    var longNumDeserialize = common.deserializeCls(messages_proto.LongValues,
+                                                   false, false);
+    var serialized = longSerialize({int_64: pos_value});
+    assert.strictEqual(typeof longDeserialize(serialized).int_64, 'string');
+    /* With the longsAsStrings option disabled, long values are represented as
+     * objects with 3 keys: low, high, and unsigned */
+    assert.strictEqual(typeof longNumDeserialize(serialized).int_64, 'object');
+  });
+});
+describe('Proto message bytes serialize and deserialize', function() {
+  var sequenceSerialize = common.serializeCls(messages_proto.SequenceValues);
+  var sequenceDeserialize = common.deserializeCls(
+      messages_proto.SequenceValues);
+  var sequenceBase64Deserialize = common.deserializeCls(
+      messages_proto.SequenceValues, true);
+  var buffer_val = new Buffer([0x69, 0xb7]);
+  var base64_val = 'abc=';
+  it('should preserve a buffer', function() {
+    var serialized = sequenceSerialize({bytes_field: buffer_val});
+    var deserialized = sequenceDeserialize(serialized);
+    assert.strictEqual(deserialized.bytes_field.compare(buffer_val), 0);
+  });
+  it('should accept base64 encoded strings', function() {
+    var serialized = sequenceSerialize({bytes_field: base64_val});
+    var deserialized = sequenceDeserialize(serialized);
+    assert.strictEqual(deserialized.bytes_field.compare(buffer_val), 0);
+  });
+  it('should output base64 encoded strings with an option set', function() {
+    var serialized = sequenceSerialize({bytes_field: base64_val});
+    var deserialized = sequenceBase64Deserialize(serialized);
+    assert.strictEqual(deserialized.bytes_field, base64_val);
+  });
+  /* The next two tests are specific tests to verify that issue
+   * https://github.com/grpc/grpc/issues/5174 has been fixed. They are skipped
+   * because they will not pass until a protobuf.js release has been published
+   * with a fix for https://github.com/dcodeIO/protobuf.js/issues/390 */
+  it.skip('should serialize a repeated field as packed by default', function() {
+    var expected_serialize = new Buffer([0x12, 0x01, 0x01, 0x0a]);
+    var serialized = sequenceSerialize({repeated_field: [10]});
+    assert.strictEqual(expected_serialize.compare(serialized), 0);
+  });
+  it.skip('should deserialize packed or unpacked repeated', function() {
+    var serialized = new Buffer([0x12, 0x01, 0x01, 0x0a]);
+    assert.doesNotThrow(function() {
+      sequenceDeserialize(serialized);
+    });
+  });
 });
diff --git a/src/node/test/test_messages.proto b/src/node/test/test_messages.proto
index c77a937d3f..9b8cb875ee 100644
--- a/src/node/test/test_messages.proto
+++ b/src/node/test/test_messages.proto
@@ -36,3 +36,8 @@ message LongValues {
   fixed64 fixed_64 = 4;
   sfixed64 sfixed_64 = 5;
 }
+
+message SequenceValues {
+  bytes bytes_field = 1;
+  repeated int32 repeated_field = 2;
+}
diff --git a/src/php/ext/grpc/call.c b/src/php/ext/grpc/call.c
index 7ba14a38d8..4f48d6f2e2 100644
--- a/src/php/ext/grpc/call.c
+++ b/src/php/ext/grpc/call.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -129,9 +129,9 @@ zval *grpc_parse_metadata_array(grpc_metadata_array *metadata_array) {
         zend_throw_exception(zend_exception_get_default(),
                              "Metadata hash somehow contains wrong types.",
                              1 TSRMLS_CC);
-          efree(str_key);
-          efree(str_val);
-          return NULL;
+        efree(str_key);
+        efree(str_val);
+        return NULL;
       }
       add_next_index_stringl(*data, str_val, elem->value_length, false);
     } else {
diff --git a/src/php/ext/grpc/channel.c b/src/php/ext/grpc/channel.c
index 60c94412dc..f0bc7340ba 100644
--- a/src/php/ext/grpc/channel.c
+++ b/src/php/ext/grpc/channel.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -141,44 +141,40 @@ PHP_METHOD(Channel, __construct) {
   HashTable *array_hash;
   zval **creds_obj = NULL;
   wrapped_grpc_channel_credentials *creds = NULL;
-  /* "s|a" == 1 string, 1 optional array */
-  if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|a", &target,
+  /* "sa" == 1 string, 1 array */
+  if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "sa", &target,
                             &target_length, &args_array) == FAILURE) {
     zend_throw_exception(spl_ce_InvalidArgumentException,
                          "Channel expects a string and an array", 1 TSRMLS_CC);
     return;
   }
-  if (args_array == NULL) {
-    channel->wrapped = grpc_insecure_channel_create(target, NULL, NULL);
-  } else {
-    array_hash = Z_ARRVAL_P(args_array);
-    if (zend_hash_find(array_hash, "credentials", sizeof("credentials"),
-                       (void **)&creds_obj) == SUCCESS) {
-      if (Z_TYPE_P(*creds_obj) == IS_NULL) {
-        creds = NULL;
-        zend_hash_del(array_hash, "credentials", 12);
-      } else if (zend_get_class_entry(*creds_obj TSRMLS_CC) !=
-          grpc_ce_channel_credentials) {
-        zend_throw_exception(spl_ce_InvalidArgumentException,
-                             "credentials must be a ChannelCredentials object",
-                             1 TSRMLS_CC);
-        return;
-      } else {
-        creds = (wrapped_grpc_channel_credentials *)zend_object_store_get_object(
-            *creds_obj TSRMLS_CC);
-        zend_hash_del(array_hash, "credentials", 12);
-      }
-    }
-    php_grpc_read_args_array(args_array, &args);
-    if (creds == NULL) {
-      channel->wrapped = grpc_insecure_channel_create(target, &args, NULL);
+  array_hash = Z_ARRVAL_P(args_array);
+  if (zend_hash_find(array_hash, "credentials", sizeof("credentials"),
+                     (void **)&creds_obj) == SUCCESS) {
+    if (Z_TYPE_P(*creds_obj) == IS_NULL) {
+      creds = NULL;
+      zend_hash_del(array_hash, "credentials", 12);
+    } else if (zend_get_class_entry(*creds_obj TSRMLS_CC) !=
+        grpc_ce_channel_credentials) {
+      zend_throw_exception(spl_ce_InvalidArgumentException,
+                           "credentials must be a ChannelCredentials object",
+                           1 TSRMLS_CC);
+      return;
     } else {
-      gpr_log(GPR_DEBUG, "Initialized secure channel");
-      channel->wrapped =
-          grpc_secure_channel_create(creds->wrapped, target, &args, NULL);
+      creds = (wrapped_grpc_channel_credentials *)zend_object_store_get_object(
+          *creds_obj TSRMLS_CC);
+      zend_hash_del(array_hash, "credentials", 12);
     }
-    efree(args.args);
   }
+  php_grpc_read_args_array(args_array, &args);
+  if (creds == NULL) {
+    channel->wrapped = grpc_insecure_channel_create(target, &args, NULL);
+  } else {
+    gpr_log(GPR_DEBUG, "Initialized secure channel");
+    channel->wrapped =
+        grpc_secure_channel_create(creds->wrapped, target, &args, NULL);
+  }
+  efree(args.args);
 }
 
 /**
diff --git a/src/php/ext/grpc/config.m4 b/src/php/ext/grpc/config.m4
index b825a84215..0fb843d51f 100755
--- a/src/php/ext/grpc/config.m4
+++ b/src/php/ext/grpc/config.m4
@@ -50,6 +50,17 @@ if test "$PHP_GRPC" != "no"; then
 
   PHP_ADD_LIBPATH($GRPC_LIBDIR)
 
+  PHP_CHECK_LIBRARY(gpr,gpr_now,
+  [
+    PHP_ADD_LIBRARY(gpr,,GRPC_SHARED_LIBADD)
+    PHP_ADD_LIBRARY(gpr)
+    AC_DEFINE(HAVE_GPRLIB,1,[ ])
+  ],[
+    AC_MSG_ERROR([wrong gpr lib version or lib not found])
+  ],[
+    -L$GRPC_LIBDIR
+  ])
+
   PHP_CHECK_LIBRARY(grpc,grpc_channel_destroy,
   [
     PHP_ADD_LIBRARY(grpc,,GRPC_SHARED_LIBADD)
diff --git a/src/php/tests/generated_code/AbstractGeneratedCodeTest.php b/src/php/tests/generated_code/AbstractGeneratedCodeTest.php
index 1fe81b9d54..f70525ef15 100644
--- a/src/php/tests/generated_code/AbstractGeneratedCodeTest.php
+++ b/src/php/tests/generated_code/AbstractGeneratedCodeTest.php
@@ -1,7 +1,7 @@
 <?php
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -106,6 +106,34 @@ abstract class AbstractGeneratedCodeTest extends PHPUnit_Framework_TestCase
         $this->assertSame(\Grpc\STATUS_CANCELLED, $status->code);
     }
 
+    public function testCallCredentialsCallback()
+    {
+        $div_arg = new math\DivArgs();
+        $call = self::$client->Div($div_arg, array(), array(
+            'call_credentials_callback' => function ($context) {
+                return array();
+            },
+        ));
+        $call->cancel();
+        list($response, $status) = $call->wait();
+        $this->assertSame(\Grpc\STATUS_CANCELLED, $status->code);
+    }
+
+    public function testCallCredentialsCallback2()
+    {
+        $div_arg = new math\DivArgs();
+        $call = self::$client->Div($div_arg);
+        $call_credentials = Grpc\CallCredentials::createFromPlugin(
+            function ($context) {
+                return array();
+            }
+        );
+        $call->setCallCredentials($call_credentials);
+        $call->cancel();
+        list($response, $status) = $call->wait();
+        $this->assertSame(\Grpc\STATUS_CANCELLED, $status->code);
+    }
+
     /**
      * @expectedException InvalidArgumentException
      */
@@ -118,6 +146,23 @@ abstract class AbstractGeneratedCodeTest extends PHPUnit_Framework_TestCase
         $invalid_client->InvalidUnaryCall($div_arg);
     }
 
+    /**
+     * @expectedException Exception
+     */
+    public function testMissingCredentials()
+    {
+        $invalid_client = new DummyInvalidClient('host', [
+        ]);
+    }
+
+    public function testPrimaryUserAgentString()
+    {
+        $invalid_client = new DummyInvalidClient('host', [
+            'credentials' => Grpc\ChannelCredentials::createInsecure(),
+            'grpc.primary_user_agent' => 'testUserAgent',
+        ]);
+    }
+
     public function testWriteFlags()
     {
         $div_arg = new math\DivArgs();
diff --git a/src/php/tests/unit_tests/CallCredentials2Test.php b/src/php/tests/unit_tests/CallCredentials2Test.php
new file mode 100644
index 0000000000..1282db6eed
--- /dev/null
+++ b/src/php/tests/unit_tests/CallCredentials2Test.php
@@ -0,0 +1,135 @@
+<?php
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+class CallCredentials2Test extends PHPUnit_Framework_TestCase
+{
+    public function setUp()
+    {
+        $credentials = Grpc\ChannelCredentials::createSsl(
+            file_get_contents(dirname(__FILE__).'/../data/ca.pem'));
+        $server_credentials = Grpc\ServerCredentials::createSsl(
+            null,
+            file_get_contents(dirname(__FILE__).'/../data/server1.key'),
+            file_get_contents(dirname(__FILE__).'/../data/server1.pem'));
+        $this->server = new Grpc\Server();
+        $this->port = $this->server->addSecureHttp2Port('0.0.0.0:0',
+                                              $server_credentials);
+        $this->server->start();
+        $this->host_override = 'foo.test.google.fr';
+        $this->channel = new Grpc\Channel(
+            'localhost:'.$this->port,
+            [
+            'grpc.ssl_target_name_override' => $this->host_override,
+            'grpc.default_authority' => $this->host_override,
+            'credentials' => $credentials,
+            ]
+        );
+    }
+
+    public function tearDown()
+    {
+        unset($this->channel);
+        unset($this->server);
+    }
+
+    public function callbackFunc($context)
+    {
+        $this->assertTrue(is_string($context->service_url));
+        $this->assertTrue(is_string($context->method_name));
+
+        return ['k1' => ['v1'], 'k2' => ['v2']];
+    }
+
+    public function testCreateFromPlugin()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $status_text = 'xyz';
+        $call = new Grpc\Call($this->channel,
+                              '/abc/dummy_method',
+                              $deadline,
+                              $this->host_override);
+
+        $call_credentials = Grpc\CallCredentials::createFromPlugin(
+            array($this, 'callbackFunc'));
+        $call->setCredentials($call_credentials);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_close);
+
+        $event = $this->server->requestCall();
+
+        $this->assertTrue(is_array($event->metadata));
+        $metadata = $event->metadata;
+        $this->assertTrue(array_key_exists('k1', $metadata));
+        $this->assertTrue(array_key_exists('k2', $metadata));
+        $this->assertSame($metadata['k1'], ['v1']);
+        $this->assertSame($metadata['k2'], ['v2']);
+
+        $this->assertSame('/abc/dummy_method', $event->method);
+        $server_call = $event->call;
+
+        $event = $server_call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_STATUS_FROM_SERVER => [
+                'metadata' => [],
+                'code' => Grpc\STATUS_OK,
+                'details' => $status_text,
+            ],
+            Grpc\OP_RECV_CLOSE_ON_SERVER => true,
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_status);
+        $this->assertFalse($event->cancelled);
+
+        $event = $call->startBatch([
+            Grpc\OP_RECV_INITIAL_METADATA => true,
+            Grpc\OP_RECV_STATUS_ON_CLIENT => true,
+        ]);
+
+        $this->assertSame([], $event->metadata);
+        $status = $event->status;
+        $this->assertSame([], $status->metadata);
+        $this->assertSame(Grpc\STATUS_OK, $status->code);
+        $this->assertSame($status_text, $status->details);
+
+        unset($call);
+        unset($server_call);
+    }
+}
diff --git a/src/php/tests/unit_tests/CallCredentials3Test.php b/src/php/tests/unit_tests/CallCredentials3Test.php
new file mode 100644
index 0000000000..a458f1d322
--- /dev/null
+++ b/src/php/tests/unit_tests/CallCredentials3Test.php
@@ -0,0 +1,136 @@
+<?php
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+class CallCredentials3Test extends PHPUnit_Framework_TestCase
+{
+    public function setUp()
+    {
+        $this->credentials = Grpc\ChannelCredentials::createSsl(
+            file_get_contents(dirname(__FILE__).'/../data/ca.pem'));
+        $server_credentials = Grpc\ServerCredentials::createSsl(
+            null,
+            file_get_contents(dirname(__FILE__).'/../data/server1.key'),
+            file_get_contents(dirname(__FILE__).'/../data/server1.pem'));
+        $this->server = new Grpc\Server();
+        $this->port = $this->server->addSecureHttp2Port('0.0.0.0:0',
+                                              $server_credentials);
+        $this->server->start();
+        $this->host_override = 'foo.test.google.fr';
+        $this->channel = new Grpc\Channel(
+            'localhost:'.$this->port,
+            [
+            'grpc.ssl_target_name_override' => $this->host_override,
+            'grpc.default_authority' => $this->host_override,
+            'credentials' => $this->credentials,
+            ]
+        );
+    }
+
+    public function tearDown()
+    {
+        unset($this->channel);
+        unset($this->server);
+    }
+
+    public function callbackFunc($context)
+    {
+        $this->assertTrue(is_string($context->service_url));
+        $this->assertTrue(is_string($context->method_name));
+
+        return ['k1' => ['v1'], 'k2' => ['v2']];
+    }
+
+    public function testCreateFromPlugin()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $status_text = 'xyz';
+        $call = new Grpc\Call($this->channel,
+                              '/abc/dummy_method',
+                              $deadline,
+                              $this->host_override);
+
+        $call_credentials = Grpc\CallCredentials::createFromPlugin(
+            [$this, 'callbackFunc']);
+        $call->setCredentials($call_credentials);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_close);
+
+        $event = $this->server->requestCall();
+
+        $this->assertTrue(is_array($event->metadata));
+        $metadata = $event->metadata;
+        $this->assertTrue(array_key_exists('k1', $metadata));
+        $this->assertTrue(array_key_exists('k2', $metadata));
+        $this->assertSame($metadata['k1'], ['v1']);
+        $this->assertSame($metadata['k2'], ['v2']);
+
+        $this->assertSame('/abc/dummy_method', $event->method);
+        $server_call = $event->call;
+
+        $event = $server_call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_STATUS_FROM_SERVER => [
+                'metadata' => [],
+                'code' => Grpc\STATUS_OK,
+                'details' => $status_text,
+            ],
+            Grpc\OP_RECV_CLOSE_ON_SERVER => true,
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_status);
+        $this->assertFalse($event->cancelled);
+
+        $event = $call->startBatch([
+            Grpc\OP_RECV_INITIAL_METADATA => true,
+            Grpc\OP_RECV_STATUS_ON_CLIENT => true,
+        ]);
+
+        $this->assertSame([], $event->metadata);
+        $status = $event->status;
+        $this->assertSame([], $status->metadata);
+        $this->assertSame(Grpc\STATUS_OK, $status->code);
+        $this->assertSame($status_text, $status->details);
+
+        unset($call);
+        unset($server_call);
+    }
+
+}
diff --git a/src/php/tests/unit_tests/CallCredentialsTest.php b/src/php/tests/unit_tests/CallCredentialsTest.php
index 0918412781..287024839d 100644
--- a/src/php/tests/unit_tests/CallCredentialsTest.php
+++ b/src/php/tests/unit_tests/CallCredentialsTest.php
@@ -1,7 +1,7 @@
 <?php
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -36,13 +36,13 @@ class CallCredentialsTest extends PHPUnit_Framework_TestCase
 {
     public function setUp()
     {
-        $credentials = Grpc\ChannelCredentials::createSsl(
+        $this->credentials = Grpc\ChannelCredentials::createSsl(
             file_get_contents(dirname(__FILE__).'/../data/ca.pem'));
-        $call_credentials = Grpc\CallCredentials::createFromPlugin(
-            array($this, 'callbackFunc'));
-        $credentials = Grpc\ChannelCredentials::createComposite(
-            $credentials,
-            $call_credentials
+        $this->call_credentials = Grpc\CallCredentials::createFromPlugin(
+            [$this, 'callbackFunc']);
+        $this->credentials = Grpc\ChannelCredentials::createComposite(
+            $this->credentials,
+            $this->call_credentials
         );
         $server_credentials = Grpc\ServerCredentials::createSsl(
             null,
@@ -58,7 +58,7 @@ class CallCredentialsTest extends PHPUnit_Framework_TestCase
             [
             'grpc.ssl_target_name_override' => $this->host_override,
             'grpc.default_authority' => $this->host_override,
-            'credentials' => $credentials,
+            'credentials' => $this->credentials,
             ]
         );
     }
@@ -134,4 +134,41 @@ class CallCredentialsTest extends PHPUnit_Framework_TestCase
         unset($call);
         unset($server_call);
     }
+
+    public function callbackFunc2($context)
+    {
+        return [];
+    }
+
+    public function testCreateComposite()
+    {
+        $call_credentials2 = Grpc\CallCredentials::createFromPlugin(
+            [$this, 'callbackFunc2']);
+        $call_credentials3 = Grpc\CallCredentials::createComposite(
+            $this->call_credentials,
+            $call_credentials2
+        );
+        $this->assertSame('Grpc\CallCredentials', get_class($call_credentials3));
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testCreateFromPluginInvalidParam()
+    {
+        $call_credentials = Grpc\CallCredentials::createFromPlugin(
+            'callbackFunc'
+        );
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testCreateCompositeInvalidParam()
+    {
+        $call_credentials3 = Grpc\CallCredentials::createComposite(
+            $this->call_credentials,
+            $this->credentials
+        );
+    }
 }
diff --git a/src/php/tests/unit_tests/CallTest.php b/src/php/tests/unit_tests/CallTest.php
index 3b697b50c3..a2522fb120 100755
--- a/src/php/tests/unit_tests/CallTest.php
+++ b/src/php/tests/unit_tests/CallTest.php
@@ -1,7 +1,7 @@
 <?php
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -91,4 +91,32 @@ class CallTest extends PHPUnit_Framework_TestCase
     {
         $this->assertTrue(is_string($this->call->getPeer()));
     }
+
+    public function testCancel()
+    {
+      $this->assertNull($this->call->cancel());
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidMetadataKey()
+    {
+        $batch = [
+            'invalid' => ['key1' => 'value1'],
+        ];
+        $result = $this->call->startBatch($batch);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidMetadataInnerValue()
+    {
+        $batch = [
+            Grpc\OP_SEND_INITIAL_METADATA => ['key1' => 'value1'],
+        ];
+        $result = $this->call->startBatch($batch);
+    }
+
 }
diff --git a/src/cpp/server/fixed_size_thread_pool.cc b/src/php/tests/unit_tests/ChannelCredentialsTest.php
index 2bdc44be2e..6d472dc876 100644
--- a/src/cpp/server/fixed_size_thread_pool.cc
+++ b/src/php/tests/unit_tests/ChannelCredentialsTest.php
@@ -1,6 +1,7 @@
+<?php
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,55 +32,42 @@
  *
  */
 
-#include <grpc++/impl/sync.h>
-#include <grpc++/impl/thd.h>
-#include "src/cpp/server/fixed_size_thread_pool.h"
-
-namespace grpc {
-
-void FixedSizeThreadPool::ThreadFunc() {
-  for (;;) {
-    // Wait until work is available or we are shutting down.
-    grpc::unique_lock<grpc::mutex> lock(mu_);
-    if (!shutdown_ && callbacks_.empty()) {
-      cv_.wait(lock);
+class ChanellCredentialsTest extends PHPUnit_Framework_TestCase
+{
+    public function setUp()
+    {
     }
-    // Drain callbacks before considering shutdown to ensure all work
-    // gets completed.
-    if (!callbacks_.empty()) {
-      auto cb = callbacks_.front();
-      callbacks_.pop();
-      lock.unlock();
-      cb();
-    } else if (shutdown_) {
-      return;
+
+    public function tearDown()
+    {
     }
-  }
-}
 
-FixedSizeThreadPool::FixedSizeThreadPool(int num_threads) : shutdown_(false) {
-  for (int i = 0; i < num_threads; i++) {
-    threads_.push_back(
-        new grpc::thread(&FixedSizeThreadPool::ThreadFunc, this));
-  }
-}
+    public function testCreateDefault()
+    {
+        $channel_credentials = Grpc\ChannelCredentials::createDefault();
+        $this->assertSame('Grpc\ChannelCredentials', get_class($channel_credentials));
+    }
 
-FixedSizeThreadPool::~FixedSizeThreadPool() {
-  {
-    grpc::lock_guard<grpc::mutex> lock(mu_);
-    shutdown_ = true;
-    cv_.notify_all();
-  }
-  for (auto t = threads_.begin(); t != threads_.end(); t++) {
-    (*t)->join();
-    delete *t;
-  }
-}
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidCreateSsl()
+    {
+        $channel_credentials = Grpc\ChannelCredentials::createSsl([]);
+    }
 
-void FixedSizeThreadPool::Add(const std::function<void()>& callback) {
-  grpc::lock_guard<grpc::mutex> lock(mu_);
-  callbacks_.push(callback);
-  cv_.notify_one();
-}
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidCreateComposite()
+    {
+        $channel_credentials = Grpc\ChannelCredentials::createComposite(
+            'something', 'something');
+    }
 
-}  // namespace grpc
+    public function testCreateInsecure()
+    {
+        $channel_credentials = Grpc\ChannelCredentials::createInsecure();
+        $this->assertNull($channel_credentials);
+    }
+}
\ No newline at end of file
diff --git a/src/php/tests/unit_tests/ChannelTest.php b/src/php/tests/unit_tests/ChannelTest.php
new file mode 100644
index 0000000000..acb8a0a70d
--- /dev/null
+++ b/src/php/tests/unit_tests/ChannelTest.php
@@ -0,0 +1,82 @@
+<?php
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+class ChannelTest extends PHPUnit_Framework_TestCase
+{
+    public function setUp()
+    {
+    }
+
+    public function tearDown()
+    {
+    }
+
+    public function testInsecureCredentials()
+    {
+        $this->channel = new Grpc\Channel(
+            'localhost:0',
+            [
+                'credentials' => Grpc\ChannelCredentials::createInsecure(),
+            ]
+        );
+        $this->assertSame('Grpc\Channel', get_class($this->channel));
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidCredentials()
+    {
+        $this->channel = new Grpc\Channel(
+            'localhost:0',
+            [
+                'credentials' => new Grpc\Timeval(100),
+            ]
+        );
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidOptionsArray()
+    {
+        $this->channel = new Grpc\Channel(
+            'localhost:0',
+            [
+                'abc' => [],
+            ]
+        );
+    }
+
+}
\ No newline at end of file
diff --git a/src/php/tests/unit_tests/EndToEndTest.php b/src/php/tests/unit_tests/EndToEndTest.php
index 5a38262451..45f6708b1f 100755
--- a/src/php/tests/unit_tests/EndToEndTest.php
+++ b/src/php/tests/unit_tests/EndToEndTest.php
@@ -1,7 +1,7 @@
 <?php
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -201,6 +201,318 @@ class EndToEndTest extends PHPUnit_Framework_TestCase
         unset($server_call);
     }
 
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidClientMessageArray()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => 'invalid',
+        ]);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidClientMessageString()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => ['message' => 0],
+        ]);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidClientMessageFlags()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => ['message' => 'abc',
+                                     'flags' => 'invalid'],
+        ]);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidServerStatusMetadata()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => ['message' => $req_text],
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_close);
+        $this->assertTrue($event->send_message);
+
+        $event = $this->server->requestCall();
+        $this->assertSame('dummy_method', $event->method);
+        $server_call = $event->call;
+
+        $event = $server_call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_MESSAGE => ['message' => $reply_text],
+            Grpc\OP_SEND_STATUS_FROM_SERVER => [
+                'metadata' => 'invalid',
+                'code' => Grpc\STATUS_OK,
+                'details' => $status_text,
+            ],
+            Grpc\OP_RECV_MESSAGE => true,
+            Grpc\OP_RECV_CLOSE_ON_SERVER => true,
+        ]);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidServerStatusCode()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => ['message' => $req_text],
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_close);
+        $this->assertTrue($event->send_message);
+
+        $event = $this->server->requestCall();
+        $this->assertSame('dummy_method', $event->method);
+        $server_call = $event->call;
+
+        $event = $server_call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_MESSAGE => ['message' => $reply_text],
+            Grpc\OP_SEND_STATUS_FROM_SERVER => [
+                'metadata' => [],
+                'code' => 'invalid',
+                'details' => $status_text,
+            ],
+            Grpc\OP_RECV_MESSAGE => true,
+            Grpc\OP_RECV_CLOSE_ON_SERVER => true,
+        ]);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testMissingServerStatusCode()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => ['message' => $req_text],
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_close);
+        $this->assertTrue($event->send_message);
+
+        $event = $this->server->requestCall();
+        $this->assertSame('dummy_method', $event->method);
+        $server_call = $event->call;
+
+        $event = $server_call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_MESSAGE => ['message' => $reply_text],
+            Grpc\OP_SEND_STATUS_FROM_SERVER => [
+                'metadata' => [],
+                'details' => $status_text,
+            ],
+            Grpc\OP_RECV_MESSAGE => true,
+            Grpc\OP_RECV_CLOSE_ON_SERVER => true,
+        ]);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidServerStatusDetails()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => ['message' => $req_text],
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_close);
+        $this->assertTrue($event->send_message);
+
+        $event = $this->server->requestCall();
+        $this->assertSame('dummy_method', $event->method);
+        $server_call = $event->call;
+
+        $event = $server_call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_MESSAGE => ['message' => $reply_text],
+            Grpc\OP_SEND_STATUS_FROM_SERVER => [
+                'metadata' => [],
+                'code' => Grpc\STATUS_OK,
+                'details' => 0,
+            ],
+            Grpc\OP_RECV_MESSAGE => true,
+            Grpc\OP_RECV_CLOSE_ON_SERVER => true,
+        ]);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testMissingServerStatusDetails()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => ['message' => $req_text],
+        ]);
+
+        $this->assertTrue($event->send_metadata);
+        $this->assertTrue($event->send_close);
+        $this->assertTrue($event->send_message);
+
+        $event = $this->server->requestCall();
+        $this->assertSame('dummy_method', $event->method);
+        $server_call = $event->call;
+
+        $event = $server_call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_MESSAGE => ['message' => $reply_text],
+            Grpc\OP_SEND_STATUS_FROM_SERVER => [
+                'metadata' => [],
+                'code' => Grpc\STATUS_OK,
+            ],
+            Grpc\OP_RECV_MESSAGE => true,
+            Grpc\OP_RECV_CLOSE_ON_SERVER => true,
+        ]);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidStartBatchKey()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            9999999 => [],
+        ]);
+    }
+
+    /**
+     * @expectedException LogicException
+     */
+    public function testInvalidStartBatch()
+    {
+        $deadline = Grpc\Timeval::infFuture();
+        $req_text = 'client_server_full_request_response';
+        $reply_text = 'reply:client_server_full_request_response';
+        $status_text = 'status:client_server_full_response_text';
+
+        $call = new Grpc\Call($this->channel,
+                              'dummy_method',
+                              $deadline);
+
+        $event = $call->startBatch([
+            Grpc\OP_SEND_INITIAL_METADATA => [],
+            Grpc\OP_SEND_CLOSE_FROM_CLIENT => true,
+            Grpc\OP_SEND_MESSAGE => ['message' => $req_text],
+            Grpc\OP_SEND_STATUS_FROM_SERVER => [
+                'metadata' => [],
+                'code' => Grpc\STATUS_OK,
+                'details' => 'abc',
+            ],
+        ]);
+    }
+
     public function testGetTarget()
     {
         $this->assertTrue(is_string($this->channel->getTarget()));
@@ -255,4 +567,36 @@ class EndToEndTest extends PHPUnit_Framework_TestCase
         $new_state = $this->channel->getConnectivityState();
         $this->assertTrue($new_state == Grpc\CHANNEL_IDLE);
     }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testGetConnectivityStateInvalidParam()
+    {
+        $this->assertTrue($this->channel->getConnectivityState(
+            new Grpc\Timeval));
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testWatchConnectivityStateInvalidParam()
+    {
+        $this->assertTrue($this->channel->watchConnectivityState(
+            0, 1000));
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testChannelConstructorInvalidParam()
+    {
+        $this->channel = new Grpc\Channel('localhost:'.$this->port, NULL);
+    }
+
+    public function testClose()
+    {
+        $this->assertNull($this->channel->close());
+    }
+
 }
diff --git a/src/cpp/server/fixed_size_thread_pool.h b/src/php/tests/unit_tests/ServerTest.php
index 394ae5821e..cde6a9a8f7 100644
--- a/src/cpp/server/fixed_size_thread_pool.h
+++ b/src/php/tests/unit_tests/ServerTest.php
@@ -1,6 +1,7 @@
+<?php
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,37 +32,40 @@
  *
  */
 
-#ifndef GRPC_INTERNAL_CPP_FIXED_SIZE_THREAD_POOL_H
-#define GRPC_INTERNAL_CPP_FIXED_SIZE_THREAD_POOL_H
+class ServerTest extends PHPUnit_Framework_TestCase
+{
+    public function setUp()
+    {
+    }
 
-#include <queue>
-#include <vector>
+    public function tearDown()
+    {
+    }
 
-#include <grpc++/impl/sync.h>
-#include <grpc++/impl/thd.h>
-#include <grpc++/support/config.h>
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidConstructor()
+    {
+        $server = new Grpc\Server('invalid_host');
+    }
 
-#include "src/cpp/server/thread_pool_interface.h"
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidAddHttp2Port()
+    {
+        $this->server = new Grpc\Server([]);
+        $this->port = $this->server->addHttp2Port(['0.0.0.0:0']);
+    }
 
-namespace grpc {
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testInvalidAddSecureHttp2Port()
+    {
+        $this->server = new Grpc\Server([]);
+        $this->port = $this->server->addSecureHttp2Port(['0.0.0.0:0']);
+    }
 
-class FixedSizeThreadPool GRPC_FINAL : public ThreadPoolInterface {
- public:
-  explicit FixedSizeThreadPool(int num_threads);
-  ~FixedSizeThreadPool();
-
-  void Add(const std::function<void()>& callback) GRPC_OVERRIDE;
-
- private:
-  grpc::mutex mu_;
-  grpc::condition_variable cv_;
-  bool shutdown_;
-  std::queue<std::function<void()>> callbacks_;
-  std::vector<grpc::thread*> threads_;
-
-  void ThreadFunc();
-};
-
-}  // namespace grpc
-
-#endif  // GRPC_INTERNAL_CPP_FIXED_SIZE_THREAD_POOL_H
+}
\ No newline at end of file
diff --git a/src/php/tests/unit_tests/TimevalTest.php b/src/php/tests/unit_tests/TimevalTest.php
index 1d2a8d303e..9e4bc294da 100755
--- a/src/php/tests/unit_tests/TimevalTest.php
+++ b/src/php/tests/unit_tests/TimevalTest.php
@@ -1,7 +1,7 @@
 <?php
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -91,4 +91,69 @@ class TimevalTest extends PHPUnit_Framework_TestCase
         $back_to_now = $deadline->subtract($delta);
         $this->assertSame(0, Grpc\Timeval::compare($back_to_now, $now));
     }
+
+    public function testSimilar()
+    {
+      $a = Grpc\Timeval::now();
+      $delta = new Grpc\Timeval(1000);
+      $b = $a->add($delta);
+      $thresh = new Grpc\Timeval(1100);
+      $this->assertTrue(Grpc\Timeval::similar($a, $b, $thresh));
+      $thresh = new Grpc\Timeval(900);
+      $this->assertFalse(Grpc\Timeval::similar($a, $b, $thresh));
+    }
+
+    public function testSleepUntil()
+    {
+        $curr_microtime = microtime(true);
+        $now = Grpc\Timeval::now();
+        $delta = new Grpc\Timeval(1000);
+        $deadline = $now->add($delta);
+        $deadline->sleepUntil();
+        $done_microtime = microtime(true);
+        $this->assertTrue(($done_microtime - $curr_microtime) > 0.0009);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testConstructorInvalidParam()
+    {
+        $delta = new Grpc\Timeval('abc');
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testAddInvalidParam()
+    {
+        $a = Grpc\Timeval::now();
+        $a->add(1000);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testSubtractInvalidParam()
+    {
+        $a = Grpc\Timeval::now();
+        $a->subtract(1000);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testCompareInvalidParam()
+    {
+        $a = Grpc\Timeval::compare(1000, 1100);
+    }
+
+    /**
+     * @expectedException InvalidArgumentException
+     */
+    public function testSimilarInvalidParam()
+    {
+        $a = Grpc\Timeval::similar(1000, 1100, 1200);
+    }
+
 }
diff --git a/src/python/grpcio/.gitignore b/src/python/grpcio/.gitignore
index 1d804e1ffc..6e5e65096c 100644
--- a/src/python/grpcio/.gitignore
+++ b/src/python/grpcio/.gitignore
@@ -14,4 +14,4 @@ nosetests.xml
 doc/
 _grpcio_metadata.py
 htmlcov/
-grpc/_adapter/credentials
+grpc/_cython/_credentials
diff --git a/src/python/grpcio/grpc/_adapter/_low.py b/src/python/grpcio/grpc/_adapter/_low.py
index a850c57741..62fd52ab40 100644
--- a/src/python/grpcio/grpc/_adapter/_low.py
+++ b/src/python/grpcio/grpc/_adapter/_low.py
@@ -27,7 +27,6 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-import pkg_resources
 import threading
 
 from grpc import _grpcio_metadata
@@ -35,7 +34,6 @@ from grpc._cython import cygrpc
 from grpc._adapter import _implementations
 from grpc._adapter import _types
 
-_ROOT_CERTIFICATES_RESOURCE_PATH = 'credentials/roots.pem'
 _USER_AGENT = 'Python-gRPC-{}'.format(_grpcio_metadata.__version__)
 
 ChannelCredentials = cygrpc.ChannelCredentials
@@ -56,9 +54,6 @@ def channel_credentials_ssl(
   pair = None
   if private_key is not None or certificate_chain is not None:
     pair = cygrpc.SslPemKeyCertPair(private_key, certificate_chain)
-  if root_certificates is None:
-    root_certificates = pkg_resources.resource_string(
-      __name__, _ROOT_CERTIFICATES_RESOURCE_PATH)
   return cygrpc.channel_credentials_ssl(root_certificates, pair)
 
 
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
index 9c85e0ee1b..800d0ea2f6 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
@@ -36,7 +36,7 @@ cdef extern from "grpc/_cython/loader.h":
   ctypedef unsigned uint32_t
   ctypedef long int64_t
 
-  int pygrpc_load_core(const char*)
+  int pygrpc_load_core(char*)
 
   void *gpr_malloc(size_t size)
   void gpr_free(void *ptr)
@@ -100,6 +100,11 @@ cdef extern from "grpc/_cython/loader.h":
     GRPC_STATUS_DATA_LOSS
     GRPC_STATUS__DO_NOT_USE
 
+  ctypedef enum grpc_ssl_roots_override_result:
+    GRPC_SSL_ROOTS_OVERRIDE_OK
+    GRPC_SSL_ROOTS_OVERRIDE_FAILED_PERMANENTLY
+    GRPC_SSL_ROOTS_OVERRIDE_FAILED
+
   struct grpc_byte_buffer_reader:
     # We don't care about the internals
     pass
@@ -338,6 +343,10 @@ cdef extern from "grpc/_cython/loader.h":
     # We don't care about the internals (and in fact don't know them)
     pass
 
+  ctypedef void (*grpc_ssl_roots_override_callback)(char **pem_root_certs)
+
+  void grpc_set_ssl_roots_override_callback(grpc_ssl_roots_override_callback cb)
+
   grpc_channel_credentials *grpc_google_default_credentials_create()
   grpc_channel_credentials *grpc_ssl_credentials_create(
       const char *pem_root_certs, grpc_ssl_pem_key_cert_pair *pem_key_cert_pair,
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/security.pxd.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/security.pxd.pxi
new file mode 100644
index 0000000000..3a952ca309
--- /dev/null
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/security.pxd.pxi
@@ -0,0 +1,32 @@
+# Copyright 2016, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+cdef grpc_ssl_roots_override_result ssl_roots_override_callback(
+    char **pem_root_certs) with gil
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/security.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/security.pyx.pxi
new file mode 100644
index 0000000000..23cee7bd6e
--- /dev/null
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/security.pyx.pxi
@@ -0,0 +1,44 @@
+# Copyright 2016, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+from libc.string cimport memcpy
+
+import pkg_resources
+
+
+cdef grpc_ssl_roots_override_result ssl_roots_override_callback(
+    char **pem_root_certs) with gil:
+  temporary_pem_root_certs = pkg_resources.resource_string(
+      'grpc._cython', '_credentials/roots.pem')
+  pem_root_certs[0] = <char *>gpr_malloc(len(temporary_pem_root_certs) + 1)
+  memcpy(
+      pem_root_certs[0], <char *>temporary_pem_root_certs,
+      len(temporary_pem_root_certs))
+  pem_root_certs[0][len(temporary_pem_root_certs)] = '\0'
+  return GRPC_SSL_ROOTS_OVERRIDE_OK
diff --git a/src/python/grpcio/grpc/_cython/cygrpc.pxd b/src/python/grpcio/grpc/_cython/cygrpc.pxd
index f22346c4f3..61b0fa788f 100644
--- a/src/python/grpcio/grpc/_cython/cygrpc.pxd
+++ b/src/python/grpcio/grpc/_cython/cygrpc.pxd
@@ -34,4 +34,5 @@ include "grpc/_cython/_cygrpc/channel.pxd.pxi"
 include "grpc/_cython/_cygrpc/credentials.pxd.pxi"
 include "grpc/_cython/_cygrpc/completion_queue.pxd.pxi"
 include "grpc/_cython/_cygrpc/records.pxd.pxi"
+include "grpc/_cython/_cygrpc/security.pxd.pxi"
 include "grpc/_cython/_cygrpc/server.pxd.pxi"
diff --git a/src/python/grpcio/grpc/_cython/cygrpc.pyx b/src/python/grpcio/grpc/_cython/cygrpc.pyx
index b1836bf5be..30cc7a132b 100644
--- a/src/python/grpcio/grpc/_cython/cygrpc.pyx
+++ b/src/python/grpcio/grpc/_cython/cygrpc.pyx
@@ -40,6 +40,7 @@ include "grpc/_cython/_cygrpc/channel.pyx.pxi"
 include "grpc/_cython/_cygrpc/credentials.pyx.pxi"
 include "grpc/_cython/_cygrpc/completion_queue.pyx.pxi"
 include "grpc/_cython/_cygrpc/records.pyx.pxi"
+include "grpc/_cython/_cygrpc/security.pyx.pxi"
 include "grpc/_cython/_cygrpc/server.pyx.pxi"
 
 #
@@ -58,6 +59,8 @@ cdef class _ModuleState:
         raise ImportError('failed to load core gRPC library')
     grpc_init()
     self.is_loaded = True
+    grpc_set_ssl_roots_override_callback(
+        <grpc_ssl_roots_override_callback>ssl_roots_override_callback)
 
   def __dealloc__(self):
     if self.is_loaded:
diff --git a/src/python/grpcio/grpc/_cython/imports.generated.c b/src/python/grpcio/grpc/_cython/imports.generated.c
index 817303c8a4..4b1860ce8c 100644
--- a/src/python/grpcio/grpc/_cython/imports.generated.c
+++ b/src/python/grpcio/grpc/_cython/imports.generated.c
@@ -137,6 +137,7 @@ grpc_auth_context_add_cstring_property_type grpc_auth_context_add_cstring_proper
 grpc_auth_context_set_peer_identity_property_name_type grpc_auth_context_set_peer_identity_property_name_import;
 grpc_channel_credentials_release_type grpc_channel_credentials_release_import;
 grpc_google_default_credentials_create_type grpc_google_default_credentials_create_import;
+grpc_set_ssl_roots_override_callback_type grpc_set_ssl_roots_override_callback_import;
 grpc_ssl_credentials_create_type grpc_ssl_credentials_create_import;
 grpc_call_credentials_release_type grpc_call_credentials_release_import;
 grpc_composite_channel_credentials_create_type grpc_composite_channel_credentials_create_import;
@@ -296,6 +297,10 @@ gpr_thd_options_is_joinable_type gpr_thd_options_is_joinable_import;
 gpr_thd_currentid_type gpr_thd_currentid_import;
 gpr_thd_join_type gpr_thd_join_import;
 
+#ifdef __cplusplus
+extern "C" {
+#endif  /* __cpluslus */
+
 void pygrpc_load_imports(HMODULE library) {
   census_initialize_import = (census_initialize_type) GetProcAddress(library, "census_initialize");
   census_shutdown_import = (census_shutdown_type) GetProcAddress(library, "census_shutdown");
@@ -397,6 +402,7 @@ void pygrpc_load_imports(HMODULE library) {
   grpc_auth_context_set_peer_identity_property_name_import = (grpc_auth_context_set_peer_identity_property_name_type) GetProcAddress(library, "grpc_auth_context_set_peer_identity_property_name");
   grpc_channel_credentials_release_import = (grpc_channel_credentials_release_type) GetProcAddress(library, "grpc_channel_credentials_release");
   grpc_google_default_credentials_create_import = (grpc_google_default_credentials_create_type) GetProcAddress(library, "grpc_google_default_credentials_create");
+  grpc_set_ssl_roots_override_callback_import = (grpc_set_ssl_roots_override_callback_type) GetProcAddress(library, "grpc_set_ssl_roots_override_callback");
   grpc_ssl_credentials_create_import = (grpc_ssl_credentials_create_type) GetProcAddress(library, "grpc_ssl_credentials_create");
   grpc_call_credentials_release_import = (grpc_call_credentials_release_type) GetProcAddress(library, "grpc_call_credentials_release");
   grpc_composite_channel_credentials_create_import = (grpc_composite_channel_credentials_create_type) GetProcAddress(library, "grpc_composite_channel_credentials_create");
@@ -557,4 +563,8 @@ void pygrpc_load_imports(HMODULE library) {
   gpr_thd_join_import = (gpr_thd_join_type) GetProcAddress(library, "gpr_thd_join");
 }
 
+#ifdef __cplusplus
+}
+#endif  /* __cpluslus */
+
 #endif /* !GPR_WIN32 */
diff --git a/src/python/grpcio/grpc/_cython/imports.generated.h b/src/python/grpcio/grpc/_cython/imports.generated.h
index 6d0a6e06c0..ca30742abc 100644
--- a/src/python/grpcio/grpc/_cython/imports.generated.h
+++ b/src/python/grpcio/grpc/_cython/imports.generated.h
@@ -361,6 +361,9 @@ extern grpc_channel_credentials_release_type grpc_channel_credentials_release_im
 typedef grpc_channel_credentials *(*grpc_google_default_credentials_create_type)(void);
 extern grpc_google_default_credentials_create_type grpc_google_default_credentials_create_import;
 #define grpc_google_default_credentials_create grpc_google_default_credentials_create_import
+typedef void(*grpc_set_ssl_roots_override_callback_type)(grpc_ssl_roots_override_callback cb);
+extern grpc_set_ssl_roots_override_callback_type grpc_set_ssl_roots_override_callback_import;
+#define grpc_set_ssl_roots_override_callback grpc_set_ssl_roots_override_callback_import
 typedef grpc_channel_credentials *(*grpc_ssl_credentials_create_type)(const char *pem_root_certs, grpc_ssl_pem_key_cert_pair *pem_key_cert_pair, void *reserved);
 extern grpc_ssl_credentials_create_type grpc_ssl_credentials_create_import;
 #define grpc_ssl_credentials_create grpc_ssl_credentials_create_import
@@ -836,8 +839,16 @@ typedef void(*gpr_thd_join_type)(gpr_thd_id t);
 extern gpr_thd_join_type gpr_thd_join_import;
 #define gpr_thd_join gpr_thd_join_import
 
+#ifdef __cplusplus
+extern "C" {
+#endif  /* __cpluslus */
+
 void pygrpc_load_imports(HMODULE library);
 
+#ifdef __cplusplus
+}
+#endif  /* __cpluslus */
+
 #else /* !GPR_WIN32 */
 
 #include <grpc/support/alloc.h>
diff --git a/src/python/grpcio/grpc/_cython/loader.c b/src/python/grpcio/grpc/_cython/loader.c
index cdd47deed3..3b72806ea1 100644
--- a/src/python/grpcio/grpc/_cython/loader.c
+++ b/src/python/grpcio/grpc/_cython/loader.c
@@ -33,6 +33,10 @@
 
 #include "loader.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif  /* __cpluslus  */
+
 #if GPR_WIN32
 
 int pygrpc_load_core(char *path) {
@@ -56,4 +60,9 @@ int pygrpc_load_core(char *path) {
 
 int pygrpc_load_core(char *path) { return 1; }
 
-#endif
+#endif  /* !GPR_WIN32 */
+
+#ifdef __cplusplus
+}
+#endif  /* __cpluslus */
+
diff --git a/src/python/grpcio/grpc/_cython/loader.h b/src/python/grpcio/grpc/_cython/loader.h
index dd31e1561b..3b8796d39f 100644
--- a/src/python/grpcio/grpc/_cython/loader.h
+++ b/src/python/grpcio/grpc/_cython/loader.h
@@ -39,7 +39,16 @@
 /* Additional inclusions not covered by "imports.generated.h" */
 #include <grpc/byte_buffer_reader.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif  /* __cpluslus */
+
 /* Attempts to load the core if necessary, and return non-zero upon succes. */
 int pygrpc_load_core(char *path);
 
+#ifdef __cplusplus
+}
+#endif  /* __cpluslus */
+
 #endif /* GRPC_RB_BYTE_BUFFER_H_ */
+
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 6e89c87436..a002a5a0a8 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -30,27 +30,49 @@
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio/grpc_core_dependencies.py.template`!!!
 
 CORE_SOURCE_FILES = [
-  'src/core/httpcli/httpcli_security_connector.c',
-  'src/core/security/base64.c',
-  'src/core/security/client_auth_filter.c',
-  'src/core/security/credentials.c',
-  'src/core/security/credentials_metadata.c',
-  'src/core/security/credentials_posix.c',
-  'src/core/security/credentials_win32.c',
-  'src/core/security/google_default_credentials.c',
-  'src/core/security/handshake.c',
-  'src/core/security/json_token.c',
-  'src/core/security/jwt_verifier.c',
-  'src/core/security/secure_endpoint.c',
-  'src/core/security/security_connector.c',
-  'src/core/security/security_context.c',
-  'src/core/security/server_auth_filter.c',
-  'src/core/security/server_secure_chttp2.c',
-  'src/core/surface/init_secure.c',
-  'src/core/surface/secure_channel_create.c',
-  'src/core/tsi/fake_transport_security.c',
-  'src/core/tsi/ssl_transport_security.c',
-  'src/core/tsi/transport_security.c',
+  'src/core/profiling/basic_timers.c',
+  'src/core/profiling/stap_timers.c',
+  'src/core/support/alloc.c',
+  'src/core/support/avl.c',
+  'src/core/support/cmdline.c',
+  'src/core/support/cpu_iphone.c',
+  'src/core/support/cpu_linux.c',
+  'src/core/support/cpu_posix.c',
+  'src/core/support/cpu_windows.c',
+  'src/core/support/env_linux.c',
+  'src/core/support/env_posix.c',
+  'src/core/support/env_win32.c',
+  'src/core/support/file.c',
+  'src/core/support/file_posix.c',
+  'src/core/support/file_win32.c',
+  'src/core/support/histogram.c',
+  'src/core/support/host_port.c',
+  'src/core/support/log.c',
+  'src/core/support/log_android.c',
+  'src/core/support/log_linux.c',
+  'src/core/support/log_posix.c',
+  'src/core/support/log_win32.c',
+  'src/core/support/murmur_hash.c',
+  'src/core/support/slice.c',
+  'src/core/support/slice_buffer.c',
+  'src/core/support/stack_lockfree.c',
+  'src/core/support/string.c',
+  'src/core/support/string_posix.c',
+  'src/core/support/string_win32.c',
+  'src/core/support/subprocess_posix.c',
+  'src/core/support/subprocess_windows.c',
+  'src/core/support/sync.c',
+  'src/core/support/sync_posix.c',
+  'src/core/support/sync_win32.c',
+  'src/core/support/thd.c',
+  'src/core/support/thd_posix.c',
+  'src/core/support/thd_win32.c',
+  'src/core/support/time.c',
+  'src/core/support/time_posix.c',
+  'src/core/support/time_precise.c',
+  'src/core/support/time_win32.c',
+  'src/core/support/tls_pthread.c',
+  'src/core/support/wrap_memcpy.c',
   'src/core/census/grpc_context.c',
   'src/core/census/grpc_filter.c',
   'src/core/channel/channel_args.c',
@@ -78,6 +100,7 @@ CORE_SOURCE_FILES = [
   'src/core/client_config/resolvers/sockaddr_resolver.c',
   'src/core/client_config/subchannel.c',
   'src/core/client_config/subchannel_factory.c',
+  'src/core/client_config/subchannel_index.c',
   'src/core/client_config/uri_parser.c',
   'src/core/compression/algorithm.c',
   'src/core/compression/message_compress.c',
@@ -178,51 +201,30 @@ CORE_SOURCE_FILES = [
   'src/core/transport/static_metadata.c',
   'src/core/transport/transport.c',
   'src/core/transport/transport_op_string.c',
-  'src/core/profiling/basic_timers.c',
-  'src/core/profiling/stap_timers.c',
-  'src/core/support/alloc.c',
-  'src/core/support/avl.c',
-  'src/core/support/cmdline.c',
-  'src/core/support/cpu_iphone.c',
-  'src/core/support/cpu_linux.c',
-  'src/core/support/cpu_posix.c',
-  'src/core/support/cpu_windows.c',
-  'src/core/support/env_linux.c',
-  'src/core/support/env_posix.c',
-  'src/core/support/env_win32.c',
-  'src/core/support/file.c',
-  'src/core/support/file_posix.c',
-  'src/core/support/file_win32.c',
-  'src/core/support/histogram.c',
-  'src/core/support/host_port.c',
-  'src/core/support/log.c',
-  'src/core/support/log_android.c',
-  'src/core/support/log_linux.c',
-  'src/core/support/log_posix.c',
-  'src/core/support/log_win32.c',
-  'src/core/support/murmur_hash.c',
-  'src/core/support/slice.c',
-  'src/core/support/slice_buffer.c',
-  'src/core/support/stack_lockfree.c',
-  'src/core/support/string.c',
-  'src/core/support/string_posix.c',
-  'src/core/support/string_win32.c',
-  'src/core/support/subprocess_posix.c',
-  'src/core/support/subprocess_windows.c',
-  'src/core/support/sync.c',
-  'src/core/support/sync_posix.c',
-  'src/core/support/sync_win32.c',
-  'src/core/support/thd.c',
-  'src/core/support/thd_posix.c',
-  'src/core/support/thd_win32.c',
-  'src/core/support/time.c',
-  'src/core/support/time_posix.c',
-  'src/core/support/time_precise.c',
-  'src/core/support/time_win32.c',
-  'src/core/support/tls_pthread.c',
-  'src/core/support/wrap_memcpy.c',
+  'src/core/httpcli/httpcli_security_connector.c',
+  'src/core/security/base64.c',
+  'src/core/security/client_auth_filter.c',
+  'src/core/security/credentials.c',
+  'src/core/security/credentials_metadata.c',
+  'src/core/security/credentials_posix.c',
+  'src/core/security/credentials_win32.c',
+  'src/core/security/google_default_credentials.c',
+  'src/core/security/handshake.c',
+  'src/core/security/json_token.c',
+  'src/core/security/jwt_verifier.c',
+  'src/core/security/secure_endpoint.c',
+  'src/core/security/security_connector.c',
+  'src/core/security/security_context.c',
+  'src/core/security/server_auth_filter.c',
+  'src/core/security/server_secure_chttp2.c',
+  'src/core/surface/init_secure.c',
+  'src/core/surface/secure_channel_create.c',
+  'src/core/tsi/fake_transport_security.c',
+  'src/core/tsi/ssl_transport_security.c',
+  'src/core/tsi/transport_security.c',
   'src/core/census/context.c',
   'src/core/census/initialize.c',
+  'src/core/census/mlog.c',
   'src/core/census/operation.c',
   'src/core/census/placeholders.c',
   'src/core/census/tracing.c',
diff --git a/src/python/grpcio/grpc_version.py b/src/python/grpcio/grpc_version.py
index db23de2fed..75b88cfd61 100644
--- a/src/python/grpcio/grpc_version.py
+++ b/src/python/grpcio/grpc_version.py
@@ -29,4 +29,4 @@
 
 # AUTO-GENERATED FROM `$REPO_ROOT/templates/src/python/grpcio/grpc_version.py.template`!!!
 
-VERSION='0.13.1rc1'
+VERSION='0.14.0.dev0'
diff --git a/src/python/grpcio/tests/unit/beta/_implementations_test.py b/src/python/grpcio/tests/unit/beta/_implementations_test.py
new file mode 100644
index 0000000000..6b32305af7
--- /dev/null
+++ b/src/python/grpcio/tests/unit/beta/_implementations_test.py
@@ -0,0 +1,54 @@
+# Copyright 2016, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Tests the implementations module of the gRPC Python Beta API."""
+
+import unittest
+
+from grpc.beta import implementations
+from tests.unit import resources
+
+
+class ChannelCredentialsTest(unittest.TestCase):
+
+  def test_runtime_provided_root_certificates(self):
+    channel_credentials = implementations.ssl_channel_credentials(
+        None, None, None)
+    self.assertIsInstance(
+        channel_credentials, implementations.ChannelCredentials)
+  
+  def test_application_provided_root_certificates(self):
+    channel_credentials = implementations.ssl_channel_credentials(
+        resources.test_root_certificates(), None, None)
+    self.assertIsInstance(
+        channel_credentials, implementations.ChannelCredentials)
+
+
+if __name__ == '__main__':
+  unittest.main(verbosity=2)
diff --git a/src/ruby/ext/grpc/extconf.rb b/src/ruby/ext/grpc/extconf.rb
index b7c6cb3d7e..6b7001a489 100644
--- a/src/ruby/ext/grpc/extconf.rb
+++ b/src/ruby/ext/grpc/extconf.rb
@@ -79,6 +79,7 @@ unless File.exist?(File.join(grpc_lib_dir, 'libgrpc.a')) or windows
   ENV['EMBED_ZLIB'] = 'true'
   ENV['ARCH_FLAGS'] = RbConfig::CONFIG['ARCH_FLAG']
   ENV['ARCH_FLAGS'] = '-arch i386 -arch x86_64' if RUBY_PLATFORM =~ /darwin/
+  ENV['CFLAGS'] = '-DGPR_BACKWARDS_COMPATIBILITY_MODE'
 
   output_dir = File.expand_path(RbConfig::CONFIG['topdir'])
   grpc_lib_dir = File.join(output_dir, 'libs', grpc_config)
diff --git a/src/ruby/ext/grpc/rb_grpc_imports.generated.c b/src/ruby/ext/grpc/rb_grpc_imports.generated.c
index d4ddb734c0..1af34d97fb 100644
--- a/src/ruby/ext/grpc/rb_grpc_imports.generated.c
+++ b/src/ruby/ext/grpc/rb_grpc_imports.generated.c
@@ -137,6 +137,7 @@ grpc_auth_context_add_cstring_property_type grpc_auth_context_add_cstring_proper
 grpc_auth_context_set_peer_identity_property_name_type grpc_auth_context_set_peer_identity_property_name_import;
 grpc_channel_credentials_release_type grpc_channel_credentials_release_import;
 grpc_google_default_credentials_create_type grpc_google_default_credentials_create_import;
+grpc_set_ssl_roots_override_callback_type grpc_set_ssl_roots_override_callback_import;
 grpc_ssl_credentials_create_type grpc_ssl_credentials_create_import;
 grpc_call_credentials_release_type grpc_call_credentials_release_import;
 grpc_composite_channel_credentials_create_type grpc_composite_channel_credentials_create_import;
@@ -397,6 +398,7 @@ void grpc_rb_load_imports(HMODULE library) {
   grpc_auth_context_set_peer_identity_property_name_import = (grpc_auth_context_set_peer_identity_property_name_type) GetProcAddress(library, "grpc_auth_context_set_peer_identity_property_name");
   grpc_channel_credentials_release_import = (grpc_channel_credentials_release_type) GetProcAddress(library, "grpc_channel_credentials_release");
   grpc_google_default_credentials_create_import = (grpc_google_default_credentials_create_type) GetProcAddress(library, "grpc_google_default_credentials_create");
+  grpc_set_ssl_roots_override_callback_import = (grpc_set_ssl_roots_override_callback_type) GetProcAddress(library, "grpc_set_ssl_roots_override_callback");
   grpc_ssl_credentials_create_import = (grpc_ssl_credentials_create_type) GetProcAddress(library, "grpc_ssl_credentials_create");
   grpc_call_credentials_release_import = (grpc_call_credentials_release_type) GetProcAddress(library, "grpc_call_credentials_release");
   grpc_composite_channel_credentials_create_import = (grpc_composite_channel_credentials_create_type) GetProcAddress(library, "grpc_composite_channel_credentials_create");
diff --git a/src/ruby/ext/grpc/rb_grpc_imports.generated.h b/src/ruby/ext/grpc/rb_grpc_imports.generated.h
index 618ae5e7fc..b61c5282b6 100644
--- a/src/ruby/ext/grpc/rb_grpc_imports.generated.h
+++ b/src/ruby/ext/grpc/rb_grpc_imports.generated.h
@@ -361,6 +361,9 @@ extern grpc_channel_credentials_release_type grpc_channel_credentials_release_im
 typedef grpc_channel_credentials *(*grpc_google_default_credentials_create_type)(void);
 extern grpc_google_default_credentials_create_type grpc_google_default_credentials_create_import;
 #define grpc_google_default_credentials_create grpc_google_default_credentials_create_import
+typedef void(*grpc_set_ssl_roots_override_callback_type)(grpc_ssl_roots_override_callback cb);
+extern grpc_set_ssl_roots_override_callback_type grpc_set_ssl_roots_override_callback_import;
+#define grpc_set_ssl_roots_override_callback grpc_set_ssl_roots_override_callback_import
 typedef grpc_channel_credentials *(*grpc_ssl_credentials_create_type)(const char *pem_root_certs, grpc_ssl_pem_key_cert_pair *pem_key_cert_pair, void *reserved);
 extern grpc_ssl_credentials_create_type grpc_ssl_credentials_create_import;
 #define grpc_ssl_credentials_create grpc_ssl_credentials_create_import
diff --git a/src/ruby/lib/grpc/version.rb b/src/ruby/lib/grpc/version.rb
index 42c94f06c8..ef0876159d 100644
--- a/src/ruby/lib/grpc/version.rb
+++ b/src/ruby/lib/grpc/version.rb
@@ -29,5 +29,5 @@
 
 # GRPC contains the General RPC module.
 module GRPC
-  VERSION = '0.13.1.pre1'
+  VERSION = '0.14.0.dev'
 end
diff --git a/src/ruby/spec/client_server_spec.rb b/src/ruby/spec/client_server_spec.rb
index 594fda1cd3..7ef534571f 100644
--- a/src/ruby/spec/client_server_spec.rb
+++ b/src/ruby/spec/client_server_spec.rb
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -198,6 +198,7 @@ shared_examples 'basic GRPC message delivery is OK' do
     # confirm the client can receive the server response and status.
     client_ops = {
       CallOps::SEND_CLOSE_FROM_CLIENT => nil,
+      CallOps::RECV_INITIAL_METADATA => nil,
       CallOps::RECV_MESSAGE => nil,
       CallOps::RECV_STATUS_ON_CLIENT => nil
     }