Merge remote-tracking branch 'upstream/master' into deadline_filter

33 files changed, 463 insertions, 206 deletions

diff --git a/src/core/ext/census/trace_context.c b/src/core/ext/census/trace_context.c
new file mode 100644
index 0000000000..fbb20d3448
--- /dev/null
+++ b/src/core/ext/census/trace_context.c
@@ -0,0 +1,86 @@
+/*
+ *
+ * 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/ext/census/trace_context.h"
+
+#include <grpc/census.h>
+#include <grpc/support/log.h>
+#include <stdbool.h>
+
+#include "third_party/nanopb/pb_decode.h"
+#include "third_party/nanopb/pb_encode.h"
+
+// This function assumes the TraceContext is valid.
+size_t encode_trace_context(google_trace_TraceContext *ctxt, uint8_t *buffer,
+                            const size_t buf_size) {
+  // Create a stream that will write to our buffer.
+  pb_ostream_t stream = pb_ostream_from_buffer(buffer, buf_size);
+
+  // encode message
+  bool status = pb_encode(&stream, google_trace_TraceContext_fields, ctxt);
+
+  if (!status) {
+    gpr_log(GPR_DEBUG, "TraceContext encoding failed: %s",
+            PB_GET_ERROR(&stream));
+    return 0;
+  }
+
+  return stream.bytes_written;
+}
+
+bool decode_trace_context(google_trace_TraceContext *ctxt, uint8_t *buffer,
+                          const size_t nbytes) {
+  // Create a stream that reads nbytes from the buffer.
+  pb_istream_t stream = pb_istream_from_buffer(buffer, nbytes);
+
+  // decode message
+  bool status = pb_decode(&stream, google_trace_TraceContext_fields, ctxt);
+
+  if (!status) {
+    gpr_log(GPR_DEBUG, "TraceContext decoding failed: %s",
+            PB_GET_ERROR(&stream));
+    return false;
+  }
+
+  // check fields
+  if (!ctxt->has_trace_id) {
+    gpr_log(GPR_DEBUG, "Invalid TraceContext: missing trace_id");
+    return false;
+  }
+  if (!ctxt->has_span_id) {
+    gpr_log(GPR_DEBUG, "Invalid TraceContext: missing span_id");
+    return false;
+  }
+
+  return true;
+}
diff --git a/src/core/ext/census/trace_context.h b/src/core/ext/census/trace_context.h
new file mode 100644
index 0000000000..ee71fef460
--- /dev/null
+++ b/src/core/ext/census/trace_context.h
@@ -0,0 +1,68 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+/* Functions for manipulating trace contexts as defined in
+   src/proto/census/trace.proto */
+#ifndef GRPC_CORE_EXT_CENSUS_TRACE_CONTEXT_H
+#define GRPC_CORE_EXT_CENSUS_TRACE_CONTEXT_H
+
+#include "src/core/ext/census/gen/trace_context.pb.h"
+
+/* Maximum number of bytes required to encode a TraceContext (31)
+1 byte for trace_id field
+1 byte for trace_id length
+1 byte for trace_id.hi field
+8 bytes for trace_id.hi (uint64_t)
+1 byte for trace_id.lo field
+8 bytes for trace_id.lo (uint64_t)
+1 byte for span_id field
+8 bytes for span_id (uint64_t)
+1 byte for is_sampled field
+1 byte for is_sampled (bool) */
+#define TRACE_MAX_CONTEXT_SIZE 31
+
+/* Encode a trace context (ctxt) into proto format to the buffer provided.  The
+size of buffer must be at least TRACE_MAX_CONTEXT_SIZE.  On success, returns the
+number of bytes successfully encoded into buffer.  On failure, returns 0. */
+size_t encode_trace_context(google_trace_TraceContext *ctxt, uint8_t *buffer,
+                            const size_t buf_size);
+
+/* Decode a proto-encoded TraceContext from the provided buffer into the
+TraceContext structure (ctxt).  The function expects to be supplied the number
+of bytes to be read from buffer (nbytes).  This function will also validate that
+the TraceContext has a span_id and a trace_id, and will return false if either
+of these do not exist. On success, returns true and false otherwise. */
+bool decode_trace_context(google_trace_TraceContext *ctxt, uint8_t *buffer,
+                          const size_t nbytes);
+
+#endif
diff --git a/src/core/ext/census/tracing.c b/src/core/ext/census/tracing.c
index 3b5d6dab2b..8f0e12296d 100644
--- a/src/core/ext/census/tracing.c
+++ b/src/core/ext/census/tracing.c
@@ -31,15 +31,19 @@
  *
  */
 
+//#include "src/core/ext/census/tracing.h"
+
 #include <grpc/census.h>
 
 /* TODO(aveitch): These are all placeholder implementations. */
 
-int census_trace_mask(const census_context *context) {
-  return CENSUS_TRACE_MASK_NONE;
-}
+// int census_trace_mask(const census_context *context) {
+//   return CENSUS_TRACE_MASK_NONE;
+// }
+
+// void census_set_trace_mask(int trace_mask) {}
 
-void census_set_trace_mask(int trace_mask) {}
+// void census_trace_print(census_context *context, uint32_t type,
+//                         const char *buffer, size_t n) {}
 
-void census_trace_print(census_context *context, uint32_t type,
-                        const char *buffer, size_t n) {}
+// void SetTracerParams(const Params& params);
diff --git a/src/core/ext/client_config/client_channel.c b/src/core/ext/client_config/client_channel.c
index 3ed66a3313..2ec37a1a4d 100644
--- a/src/core/ext/client_config/client_channel.c
+++ b/src/core/ext/client_config/client_channel.c
@@ -42,6 +42,7 @@
 #include <grpc/support/sync.h>
 #include <grpc/support/useful.h>
 
+#include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/ext/client_config/subchannel.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/channel/connected_channel.h"
@@ -64,6 +65,8 @@ typedef struct client_channel_channel_data {
   grpc_resolver *resolver;
   /** have we started resolving this channel */
   bool started_resolving;
+  /** client channel factory */
+  grpc_client_channel_factory *client_channel_factory;
 
   /** mutex protecting client configuration, including all
       variables below in this data structure */
@@ -174,20 +177,26 @@ static void on_resolver_result_changed(grpc_exec_ctx *exec_ctx, void *arg,
   grpc_error *state_error = GRPC_ERROR_CREATE("No load balancing policy");
 
   if (chand->resolver_result != NULL) {
-    lb_policy = grpc_resolver_result_get_lb_policy(chand->resolver_result);
+    grpc_lb_policy_args lb_policy_args;
+    lb_policy_args.addresses =
+        grpc_resolver_result_get_addresses(chand->resolver_result);
+    lb_policy_args.additional_args =
+        grpc_resolver_result_get_lb_policy_args(chand->resolver_result);
+    lb_policy_args.client_channel_factory = chand->client_channel_factory;
+    lb_policy = grpc_lb_policy_create(
+        exec_ctx,
+        grpc_resolver_result_get_lb_policy_name(chand->resolver_result),
+        &lb_policy_args);
     if (lb_policy != NULL) {
-      GRPC_LB_POLICY_REF(lb_policy, "channel");
       GRPC_LB_POLICY_REF(lb_policy, "config_change");
       GRPC_ERROR_UNREF(state_error);
       state =
           grpc_lb_policy_check_connectivity(exec_ctx, lb_policy, &state_error);
     }
-
     grpc_resolver_result_unref(exec_ctx, chand->resolver_result);
+    chand->resolver_result = NULL;
   }
 
-  chand->resolver_result = NULL;
-
   if (lb_policy != NULL) {
     grpc_pollset_set_add_pollset_set(exec_ctx, lb_policy->interested_parties,
                                      chand->interested_parties);
@@ -347,6 +356,9 @@ static void cc_destroy_channel_elem(grpc_exec_ctx *exec_ctx,
     grpc_resolver_shutdown(exec_ctx, chand->resolver);
     GRPC_RESOLVER_UNREF(exec_ctx, chand->resolver, "channel");
   }
+  if (chand->client_channel_factory != NULL) {
+    grpc_client_channel_factory_unref(exec_ctx, chand->client_channel_factory);
+  }
   if (chand->lb_policy != NULL) {
     grpc_pollset_set_del_pollset_set(exec_ctx,
                                      chand->lb_policy->interested_parties,
@@ -796,10 +808,12 @@ const grpc_channel_filter grpc_client_channel_filter = {
     "client-channel",
 };
 
-void grpc_client_channel_set_resolver(grpc_exec_ctx *exec_ctx,
-                                      grpc_channel_stack *channel_stack,
-                                      grpc_resolver *resolver) {
+void grpc_client_channel_finish_initialization(
+    grpc_exec_ctx *exec_ctx, grpc_channel_stack *channel_stack,
+    grpc_resolver *resolver,
+    grpc_client_channel_factory *client_channel_factory) {
   /* post construction initialization: set the transport setup pointer */
+  GPR_ASSERT(client_channel_factory != NULL);
   grpc_channel_element *elem = grpc_channel_stack_last_element(channel_stack);
   channel_data *chand = elem->channel_data;
   gpr_mu_lock(&chand->mu);
@@ -813,6 +827,8 @@ void grpc_client_channel_set_resolver(grpc_exec_ctx *exec_ctx,
     grpc_resolver_next(exec_ctx, resolver, &chand->resolver_result,
                        &chand->on_resolver_result_changed);
   }
+  chand->client_channel_factory = client_channel_factory;
+  grpc_client_channel_factory_ref(client_channel_factory);
   gpr_mu_unlock(&chand->mu);
 }
 
diff --git a/src/core/ext/client_config/client_channel.h b/src/core/ext/client_config/client_channel.h
index 1e47ad34ad..abb5ac4d87 100644
--- a/src/core/ext/client_config/client_channel.h
+++ b/src/core/ext/client_config/client_channel.h
@@ -34,6 +34,7 @@
 #ifndef GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_H
 #define GRPC_CORE_EXT_CLIENT_CONFIG_CLIENT_CHANNEL_H
 
+#include "src/core/ext/client_config/client_channel_factory.h"
 #include "src/core/ext/client_config/resolver.h"
 #include "src/core/lib/channel/channel_stack.h"
 
@@ -46,12 +47,12 @@
 
 extern const grpc_channel_filter grpc_client_channel_filter;
 
-/* post-construction initializer to let the client channel know which
-   transport setup it should cancel upon destruction, or initiate when it needs
-   a connection */
-void grpc_client_channel_set_resolver(grpc_exec_ctx *exec_ctx,
-                                      grpc_channel_stack *channel_stack,
-                                      grpc_resolver *resolver);
+/* Post-construction initializer to give the client channel its resolver
+   and factory. */
+void grpc_client_channel_finish_initialization(
+    grpc_exec_ctx *exec_ctx, grpc_channel_stack *channel_stack,
+    grpc_resolver *resolver,
+    grpc_client_channel_factory *client_channel_factory);
 
 grpc_connectivity_state grpc_client_channel_check_connectivity_state(
     grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, int try_to_connect);
diff --git a/src/core/ext/client_config/lb_policy_factory.c b/src/core/ext/client_config/lb_policy_factory.c
index f86117aa38..c17af91a09 100644
--- a/src/core/ext/client_config/lb_policy_factory.c
+++ b/src/core/ext/client_config/lb_policy_factory.c
@@ -34,6 +34,7 @@
 #include <string.h>
 
 #include <grpc/support/alloc.h>
+#include <grpc/support/string_util.h>
 
 #include "src/core/ext/client_config/lb_policy_factory.h"
 
@@ -46,6 +47,25 @@ grpc_lb_addresses* grpc_lb_addresses_create(size_t num_addresses) {
   return addresses;
 }
 
+grpc_lb_addresses* grpc_lb_addresses_copy(grpc_lb_addresses* addresses,
+                                          void* (*user_data_copy)(void*)) {
+  grpc_lb_addresses* new_addresses =
+      grpc_lb_addresses_create(addresses->num_addresses);
+  memcpy(new_addresses->addresses, addresses->addresses,
+         sizeof(grpc_lb_address) * addresses->num_addresses);
+  for (size_t i = 0; i < addresses->num_addresses; ++i) {
+    if (new_addresses->addresses[i].balancer_name != NULL) {
+      new_addresses->addresses[i].balancer_name =
+          gpr_strdup(new_addresses->addresses[i].balancer_name);
+    }
+    if (user_data_copy != NULL) {
+      new_addresses->addresses[i].user_data =
+          user_data_copy(new_addresses->addresses[i].user_data);
+    }
+  }
+  return new_addresses;
+}
+
 void grpc_lb_addresses_set_address(grpc_lb_addresses* addresses, size_t index,
                                    void* address, size_t address_len,
                                    bool is_balancer, char* balancer_name,
diff --git a/src/core/ext/client_config/lb_policy_factory.h b/src/core/ext/client_config/lb_policy_factory.h
index b31179cf80..54408c6308 100644
--- a/src/core/ext/client_config/lb_policy_factory.h
+++ b/src/core/ext/client_config/lb_policy_factory.h
@@ -36,9 +36,9 @@
 
 #include "src/core/ext/client_config/client_channel_factory.h"
 #include "src/core/ext/client_config/lb_policy.h"
-#include "src/core/ext/client_config/resolver_result.h"
 
 #include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/resolve_address.h"
 
 typedef struct grpc_lb_policy_factory grpc_lb_policy_factory;
 typedef struct grpc_lb_policy_factory_vtable grpc_lb_policy_factory_vtable;
@@ -68,6 +68,11 @@ typedef struct grpc_lb_addresses {
  * \a num_addresses addresses. */
 grpc_lb_addresses *grpc_lb_addresses_create(size_t num_addresses);
 
+/** Creates a copy of \a addresses.  If \a user_data_copy is not NULL,
+ * it will be invoked to copy the \a user_data field of each address. */
+grpc_lb_addresses *grpc_lb_addresses_copy(grpc_lb_addresses *addresses,
+                                          void *(*user_data_copy)(void *));
+
 /** Sets the value of the address at index \a index of \a addresses.
  * \a address is a socket address of length \a address_len.
  * Takes ownership of \a balancer_name. */
@@ -82,9 +87,13 @@ void grpc_lb_addresses_destroy(grpc_lb_addresses *addresses,
                                void (*user_data_destroy)(void *));
 
 /** Arguments passed to LB policies. */
+/* TODO(roth, ctiller): Consider replacing this struct with
+   grpc_channel_args.  See comment in resolver_result.h for details. */
 typedef struct grpc_lb_policy_args {
   grpc_lb_addresses *addresses;
   grpc_client_channel_factory *client_channel_factory;
+  /* Can be used to pass implementation-specific parameters to the LB policy. */
+  grpc_channel_args *additional_args;
 } grpc_lb_policy_args;
 
 struct grpc_lb_policy_factory_vtable {
diff --git a/src/core/ext/client_config/resolver_factory.h b/src/core/ext/client_config/resolver_factory.h
index f69bf79564..9ec5b9a70e 100644
--- a/src/core/ext/client_config/resolver_factory.h
+++ b/src/core/ext/client_config/resolver_factory.h
@@ -47,10 +47,7 @@ struct grpc_resolver_factory {
   const grpc_resolver_factory_vtable *vtable;
 };
 
-typedef struct grpc_resolver_args {
-  grpc_uri *uri;
-  grpc_client_channel_factory *client_channel_factory;
-} grpc_resolver_args;
+typedef struct grpc_resolver_args { grpc_uri *uri; } grpc_resolver_args;
 
 struct grpc_resolver_factory_vtable {
   void (*ref)(grpc_resolver_factory *factory);
diff --git a/src/core/ext/client_config/resolver_registry.c b/src/core/ext/client_config/resolver_registry.c
index e7a4abd568..b5308a140c 100644
--- a/src/core/ext/client_config/resolver_registry.c
+++ b/src/core/ext/client_config/resolver_registry.c
@@ -128,15 +128,13 @@ static grpc_resolver_factory *resolve_factory(const char *target,
   return factory;
 }
 
-grpc_resolver *grpc_resolver_create(
-    const char *target, grpc_client_channel_factory *client_channel_factory) {
+grpc_resolver *grpc_resolver_create(const char *target) {
   grpc_uri *uri = NULL;
   grpc_resolver_factory *factory = resolve_factory(target, &uri);
   grpc_resolver *resolver;
   grpc_resolver_args args;
   memset(&args, 0, sizeof(args));
   args.uri = uri;
-  args.client_channel_factory = client_channel_factory;
   resolver = grpc_resolver_factory_create_resolver(factory, &args);
   grpc_uri_destroy(uri);
   return resolver;
diff --git a/src/core/ext/client_config/resolver_registry.h b/src/core/ext/client_config/resolver_registry.h
index 5ef1383cd3..92e248d548 100644
--- a/src/core/ext/client_config/resolver_registry.h
+++ b/src/core/ext/client_config/resolver_registry.h
@@ -55,8 +55,7 @@ void grpc_register_resolver_type(grpc_resolver_factory *factory);
     If a resolver factory was found, use it to instantiate a resolver and
     return it.
     If a resolver factory was not found, return NULL. */
-grpc_resolver *grpc_resolver_create(
-    const char *target, grpc_client_channel_factory *client_channel_factory);
+grpc_resolver *grpc_resolver_create(const char *target);
 
 /** Find a resolver factory given a name and return an (owned-by-the-caller)
  *  reference to it */
diff --git a/src/core/ext/client_config/resolver_result.c b/src/core/ext/client_config/resolver_result.c
index 242989a0da..59c9e7dc25 100644
--- a/src/core/ext/client_config/resolver_result.c
+++ b/src/core/ext/client_config/resolver_result.c
@@ -34,40 +34,54 @@
 #include <string.h>
 
 #include <grpc/support/alloc.h>
+#include <grpc/support/string_util.h>
+
+#include "src/core/lib/channel/channel_args.h"
 
 struct grpc_resolver_result {
   gpr_refcount refs;
-  grpc_lb_policy* lb_policy;
+  grpc_lb_addresses* addresses;
+  char* lb_policy_name;
+  grpc_channel_args* lb_policy_args;
 };
 
-grpc_resolver_result* grpc_resolver_result_create() {
-  grpc_resolver_result* c = gpr_malloc(sizeof(*c));
-  memset(c, 0, sizeof(*c));
-  gpr_ref_init(&c->refs, 1);
-  return c;
+grpc_resolver_result* grpc_resolver_result_create(
+    grpc_lb_addresses* addresses, const char* lb_policy_name,
+    grpc_channel_args* lb_policy_args) {
+  grpc_resolver_result* result = gpr_malloc(sizeof(*result));
+  memset(result, 0, sizeof(*result));
+  gpr_ref_init(&result->refs, 1);
+  result->addresses = addresses;
+  result->lb_policy_name = gpr_strdup(lb_policy_name);
+  result->lb_policy_args = lb_policy_args;
+  return result;
 }
 
-void grpc_resolver_result_ref(grpc_resolver_result* c) { gpr_ref(&c->refs); }
+void grpc_resolver_result_ref(grpc_resolver_result* result) {
+  gpr_ref(&result->refs);
+}
 
 void grpc_resolver_result_unref(grpc_exec_ctx* exec_ctx,
-                                grpc_resolver_result* c) {
-  if (gpr_unref(&c->refs)) {
-    if (c->lb_policy != NULL) {
-      GRPC_LB_POLICY_UNREF(exec_ctx, c->lb_policy, "resolver_result");
-    }
-    gpr_free(c);
+                                grpc_resolver_result* result) {
+  if (gpr_unref(&result->refs)) {
+    grpc_lb_addresses_destroy(result->addresses, NULL /* user_data_destroy */);
+    gpr_free(result->lb_policy_name);
+    grpc_channel_args_destroy(result->lb_policy_args);
+    gpr_free(result);
   }
 }
 
-void grpc_resolver_result_set_lb_policy(grpc_resolver_result* c,
-                                        grpc_lb_policy* lb_policy) {
-  GPR_ASSERT(c->lb_policy == NULL);
-  if (lb_policy) {
-    GRPC_LB_POLICY_REF(lb_policy, "resolver_result");
-  }
-  c->lb_policy = lb_policy;
+grpc_lb_addresses* grpc_resolver_result_get_addresses(
+    grpc_resolver_result* result) {
+  return result->addresses;
+}
+
+const char* grpc_resolver_result_get_lb_policy_name(
+    grpc_resolver_result* result) {
+  return result->lb_policy_name;
 }
 
-grpc_lb_policy* grpc_resolver_result_get_lb_policy(grpc_resolver_result* c) {
-  return c->lb_policy;
+grpc_channel_args* grpc_resolver_result_get_lb_policy_args(
+    grpc_resolver_result* result) {
+  return result->lb_policy_args;
 }
diff --git a/src/core/ext/client_config/resolver_result.h b/src/core/ext/client_config/resolver_result.h
index 5a69d81990..d4118b90e8 100644
--- a/src/core/ext/client_config/resolver_result.h
+++ b/src/core/ext/client_config/resolver_result.h
@@ -32,22 +32,40 @@
 #ifndef GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_RESULT_H
 #define GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_RESULT_H
 
-#include <stdbool.h>
-
-#include "src/core/ext/client_config/lb_policy.h"
+#include "src/core/ext/client_config/lb_policy_factory.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 
+// TODO(roth, ctiller): In the long term, we are considering replacing
+// the resolver_result data structure with grpc_channel_args.  The idea is
+// that the resolver will return a set of channel args that contains the
+// information that is currently in the resolver_result struct.  For
+// example, there will be specific args indicating the set of addresses
+// and the name of the LB policy to instantiate.  Note that if we did
+// this, we would probably want to change the data structure of
+// grpc_channel_args such to a hash table or AVL or some other data
+// structure that does not require linear search to find keys.
+
 /// Results reported from a grpc_resolver.
 typedef struct grpc_resolver_result grpc_resolver_result;
 
-grpc_resolver_result* grpc_resolver_result_create();
+/// Takes ownership of \a addresses and \a lb_policy_args.
+grpc_resolver_result* grpc_resolver_result_create(
+    grpc_lb_addresses* addresses, const char* lb_policy_name,
+    grpc_channel_args* lb_policy_args);
 void grpc_resolver_result_ref(grpc_resolver_result* result);
 void grpc_resolver_result_unref(grpc_exec_ctx* exec_ctx,
                                 grpc_resolver_result* result);
 
-void grpc_resolver_result_set_lb_policy(grpc_resolver_result* result,
-                                        grpc_lb_policy* lb_policy);
-grpc_lb_policy* grpc_resolver_result_get_lb_policy(
+/// Caller does NOT take ownership of result.
+grpc_lb_addresses* grpc_resolver_result_get_addresses(
+    grpc_resolver_result* result);
+
+/// Caller does NOT take ownership of result.
+const char* grpc_resolver_result_get_lb_policy_name(
+    grpc_resolver_result* result);
+
+/// Caller does NOT take ownership of result.
+grpc_channel_args* grpc_resolver_result_get_lb_policy_args(
     grpc_resolver_result* result);
 
 #endif /* GRPC_CORE_EXT_CLIENT_CONFIG_RESOLVER_RESULT_H */
diff --git a/src/core/ext/resolver/dns/native/dns_resolver.c b/src/core/ext/resolver/dns/native/dns_resolver.c
index 63682db7de..1b85d2d634 100644
--- a/src/core/ext/resolver/dns/native/dns_resolver.c
+++ b/src/core/ext/resolver/dns/native/dns_resolver.c
@@ -37,7 +37,6 @@
 #include <grpc/support/host_port.h>
 #include <grpc/support/string_util.h>
 
-#include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/timer.h"
@@ -58,8 +57,6 @@ typedef struct {
   char *name;
   /** default port to use */
   char *default_port;
-  /** subchannel factory */
-  grpc_client_channel_factory *client_channel_factory;
   /** load balancing policy name */
   char *lb_policy_name;
 
@@ -166,31 +163,20 @@ static void dns_on_resolved(grpc_exec_ctx *exec_ctx, void *arg,
                             grpc_error *error) {
   dns_resolver *r = arg;
   grpc_resolver_result *result = NULL;
-  grpc_lb_policy *lb_policy;
   gpr_mu_lock(&r->mu);
   GPR_ASSERT(r->resolving);
   r->resolving = 0;
   if (r->addresses != NULL) {
-    grpc_lb_policy_args lb_policy_args;
-    memset(&lb_policy_args, 0, sizeof(lb_policy_args));
-    lb_policy_args.addresses = grpc_lb_addresses_create(r->addresses->naddrs);
+    grpc_lb_addresses *addresses =
+        grpc_lb_addresses_create(r->addresses->naddrs);
     for (size_t i = 0; i < r->addresses->naddrs; ++i) {
       grpc_lb_addresses_set_address(
-          lb_policy_args.addresses, i, &r->addresses->addrs[i].addr,
+          addresses, i, &r->addresses->addrs[i].addr,
           r->addresses->addrs[i].len, false /* is_balancer */,
           NULL /* balancer_name */, NULL /* user_data */);
     }
     grpc_resolved_addresses_destroy(r->addresses);
-    lb_policy_args.client_channel_factory = r->client_channel_factory;
-    lb_policy =
-        grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
-    grpc_lb_addresses_destroy(lb_policy_args.addresses,
-                              NULL /* user_data_destroy */);
-    result = grpc_resolver_result_create();
-    if (lb_policy != NULL) {
-      grpc_resolver_result_set_lb_policy(result, lb_policy);
-      GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "construction");
-    }
+    result = grpc_resolver_result_create(addresses, r->lb_policy_name, NULL);
   } else {
     gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
     gpr_timespec next_try = gpr_backoff_step(&r->backoff_state, now);
@@ -251,7 +237,6 @@ static void dns_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   if (r->resolved_result) {
     grpc_resolver_result_unref(exec_ctx, r->resolved_result);
   }
-  grpc_client_channel_factory_unref(exec_ctx, r->client_channel_factory);
   gpr_free(r->name);
   gpr_free(r->default_port);
   gpr_free(r->lb_policy_name);
@@ -278,10 +263,8 @@ static grpc_resolver *dns_create(grpc_resolver_args *args,
   grpc_resolver_init(&r->base, &dns_resolver_vtable);
   r->name = gpr_strdup(path);
   r->default_port = gpr_strdup(default_port);
-  r->client_channel_factory = args->client_channel_factory;
   gpr_backoff_init(&r->backoff_state, BACKOFF_MULTIPLIER, BACKOFF_JITTER,
                    BACKOFF_MIN_SECONDS * 1000, BACKOFF_MAX_SECONDS * 1000);
-  grpc_client_channel_factory_ref(r->client_channel_factory);
   r->lb_policy_name = gpr_strdup(lb_policy_name);
   return &r->base;
 }
diff --git a/src/core/ext/resolver/sockaddr/sockaddr_resolver.c b/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
index fbfe5d774b..ced4fb024c 100644
--- a/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
+++ b/src/core/ext/resolver/sockaddr/sockaddr_resolver.c
@@ -40,7 +40,6 @@
 #include <grpc/support/port_platform.h>
 #include <grpc/support/string_util.h>
 
-#include "src/core/ext/client_config/lb_policy_registry.h"
 #include "src/core/ext/client_config/parse_address.h"
 #include "src/core/ext/client_config/resolver_registry.h"
 #include "src/core/lib/iomgr/resolve_address.h"
@@ -52,8 +51,6 @@ typedef struct {
   grpc_resolver base;
   /** refcount */
   gpr_refcount refs;
-  /** subchannel factory */
-  grpc_client_channel_factory *client_channel_factory;
   /** load balancing policy name */
   char *lb_policy_name;
 
@@ -122,17 +119,10 @@ static void sockaddr_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
 static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
                                               sockaddr_resolver *r) {
   if (r->next_completion != NULL && !r->published) {
-    grpc_resolver_result *result = grpc_resolver_result_create();
-    grpc_lb_policy_args lb_policy_args;
-    memset(&lb_policy_args, 0, sizeof(lb_policy_args));
-    lb_policy_args.addresses = r->addresses;
-    lb_policy_args.client_channel_factory = r->client_channel_factory;
-    grpc_lb_policy *lb_policy =
-        grpc_lb_policy_create(exec_ctx, r->lb_policy_name, &lb_policy_args);
-    grpc_resolver_result_set_lb_policy(result, lb_policy);
-    GRPC_LB_POLICY_UNREF(exec_ctx, lb_policy, "sockaddr");
     r->published = true;
-    *r->target_result = result;
+    *r->target_result = grpc_resolver_result_create(
+        grpc_lb_addresses_copy(r->addresses, NULL /* user_data_copy */),
+        r->lb_policy_name, NULL);
     grpc_exec_ctx_sched(exec_ctx, r->next_completion, GRPC_ERROR_NONE, NULL);
     r->next_completion = NULL;
   }
@@ -141,7 +131,6 @@ static void sockaddr_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
 static void sockaddr_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   sockaddr_resolver *r = (sockaddr_resolver *)gr;
   gpr_mu_destroy(&r->mu);
-  grpc_client_channel_factory_unref(exec_ctx, r->client_channel_factory);
   grpc_lb_addresses_destroy(r->addresses, NULL /* user_data_destroy */);
   gpr_free(r->lb_policy_name);
   gpr_free(r);
@@ -243,8 +232,6 @@ static grpc_resolver *sockaddr_create(
   gpr_ref_init(&r->refs, 1);
   gpr_mu_init(&r->mu);
   grpc_resolver_init(&r->base, &sockaddr_resolver_vtable);
-  r->client_channel_factory = args->client_channel_factory;
-  grpc_client_channel_factory_ref(r->client_channel_factory);
 
   return &r->base;
 }
diff --git a/src/core/ext/transport/chttp2/client/insecure/channel_create.c b/src/core/ext/transport/chttp2/client/insecure/channel_create.c
index cbaa75a90a..ddc00bd79f 100644
--- a/src/core/ext/transport/chttp2/client/insecure/channel_create.c
+++ b/src/core/ext/transport/chttp2/client/insecure/channel_create.c
@@ -160,7 +160,6 @@ typedef struct {
   grpc_client_channel_factory base;
   gpr_refcount refs;
   grpc_channel_args *merge_args;
-  grpc_channel *master;
 } client_channel_factory;
 
 static void client_channel_factory_ref(
@@ -173,10 +172,6 @@ static void client_channel_factory_unref(
     grpc_exec_ctx *exec_ctx, grpc_client_channel_factory *cc_factory) {
   client_channel_factory *f = (client_channel_factory *)cc_factory;
   if (gpr_unref(&f->refs)) {
-    if (f->master != NULL) {
-      GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, f->master,
-                                  "client_channel_factory");
-    }
     grpc_channel_args_destroy(f->merge_args);
     gpr_free(f);
   }
@@ -210,15 +205,15 @@ static grpc_channel *client_channel_factory_create_channel(
   grpc_channel *channel = grpc_channel_create(exec_ctx, target, final_args,
                                               GRPC_CLIENT_CHANNEL, NULL);
   grpc_channel_args_destroy(final_args);
-  grpc_resolver *resolver = grpc_resolver_create(target, &f->base);
+  grpc_resolver *resolver = grpc_resolver_create(target);
   if (!resolver) {
     GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, channel,
                                 "client_channel_factory_create_channel");
     return NULL;
   }
 
-  grpc_client_channel_set_resolver(
-      exec_ctx, grpc_channel_get_channel_stack(channel), resolver);
+  grpc_client_channel_finish_initialization(
+      exec_ctx, grpc_channel_get_channel_stack(channel), resolver, &f->base);
   GRPC_RESOLVER_UNREF(exec_ctx, resolver, "create_channel");
 
   return channel;
@@ -250,12 +245,8 @@ grpc_channel *grpc_insecure_channel_create(const char *target,
 
   grpc_channel *channel = client_channel_factory_create_channel(
       &exec_ctx, &f->base, target, GRPC_CLIENT_CHANNEL_TYPE_REGULAR, NULL);
-  if (channel != NULL) {
-    f->master = channel;
-    GRPC_CHANNEL_INTERNAL_REF(f->master, "grpc_insecure_channel_create");
-  }
-  grpc_client_channel_factory_unref(&exec_ctx, &f->base);
 
+  grpc_client_channel_factory_unref(&exec_ctx, &f->base);
   grpc_exec_ctx_finish(&exec_ctx);
 
   return channel != NULL ? channel : grpc_lame_client_channel_create(
diff --git a/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c b/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
index 9e2bdd758f..f36fbbfc57 100644
--- a/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
+++ b/src/core/ext/transport/chttp2/client/secure/secure_channel_create.c
@@ -220,7 +220,6 @@ typedef struct {
   gpr_refcount refs;
   grpc_channel_args *merge_args;
   grpc_channel_security_connector *security_connector;
-  grpc_channel *master;
 } client_channel_factory;
 
 static void client_channel_factory_ref(
@@ -235,10 +234,6 @@ static void client_channel_factory_unref(
   if (gpr_unref(&f->refs)) {
     GRPC_SECURITY_CONNECTOR_UNREF(&f->security_connector->base,
                                   "client_channel_factory");
-    if (f->master != NULL) {
-      GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, f->master,
-                                  "client_channel_factory");
-    }
     grpc_channel_args_destroy(f->merge_args);
     gpr_free(f);
   }
@@ -276,10 +271,10 @@ static grpc_channel *client_channel_factory_create_channel(
                                               GRPC_CLIENT_CHANNEL, NULL);
   grpc_channel_args_destroy(final_args);
 
-  grpc_resolver *resolver = grpc_resolver_create(target, &f->base);
+  grpc_resolver *resolver = grpc_resolver_create(target);
   if (resolver != NULL) {
-    grpc_client_channel_set_resolver(
-        exec_ctx, grpc_channel_get_channel_stack(channel), resolver);
+    grpc_client_channel_finish_initialization(
+        exec_ctx, grpc_channel_get_channel_stack(channel), resolver, &f->base);
     GRPC_RESOLVER_UNREF(exec_ctx, resolver, "create");
   } else {
     GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, channel,
@@ -356,10 +351,6 @@ grpc_channel *grpc_secure_channel_create(grpc_channel_credentials *creds,
 
   grpc_channel *channel = client_channel_factory_create_channel(
       &exec_ctx, &f->base, target, GRPC_CLIENT_CHANNEL_TYPE_REGULAR, NULL);
-  if (channel != NULL) {
-    f->master = channel;
-    GRPC_CHANNEL_INTERNAL_REF(f->master, "grpc_secure_channel_create");
-  }
 
   grpc_client_channel_factory_unref(&exec_ctx, &f->base);
   grpc_exec_ctx_finish(&exec_ctx);
diff --git a/src/php/lib/Grpc/BaseStub.php b/src/php/lib/Grpc/BaseStub.php
index d850eebc78..8a7f6572a6 100644
--- a/src/php/lib/Grpc/BaseStub.php
+++ b/src/php/lib/Grpc/BaseStub.php
@@ -182,6 +182,7 @@ class BaseStub
         } else {
             $hostname = $this->hostname;
         }
+
         return 'https://'.$hostname.$service_name;
     }
 
diff --git a/src/php/tests/interop/interop_client.php b/src/php/tests/interop/interop_client.php
index 94ceeda02c..4bc4589956 100755
--- a/src/php/tests/interop/interop_client.php
+++ b/src/php/tests/interop/interop_client.php
@@ -70,7 +70,8 @@ function hardAssertIfStatusOk($status)
  */
 function emptyUnary($stub)
 {
-    list($result, $status) = $stub->EmptyCall(new grpc\testing\EmptyMessage())->wait();
+    list($result, $status) =
+        $stub->EmptyCall(new grpc\testing\EmptyMessage())->wait();
     hardAssertIfStatusOk($status);
     hardAssert($result !== null, 'Call completed with a null response');
 }
@@ -92,8 +93,8 @@ function largeUnary($stub)
  * @param $fillUsername boolean whether to fill result with username
  * @param $fillOauthScope boolean whether to fill result with oauth scope
  */
-function performLargeUnary($stub, $fillUsername = false, $fillOauthScope = false,
-                           $callback = false)
+function performLargeUnary($stub, $fillUsername = false,
+                           $fillOauthScope = false, $callback = false)
 {
     $request_len = 271828;
     $response_len = 314159;
@@ -118,11 +119,11 @@ function performLargeUnary($stub, $fillUsername = false, $fillOauthScope = false
     hardAssert($result !== null, 'Call returned a null response');
     $payload = $result->getPayload();
     hardAssert($payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
-         'Payload had the wrong type');
+               'Payload had the wrong type');
     hardAssert(strlen($payload->getBody()) === $response_len,
-         'Payload had the wrong length');
+               'Payload had the wrong length');
     hardAssert($payload->getBody() === str_repeat("\0", $response_len),
-         'Payload had the wrong content');
+               'Payload had the wrong content');
 
     return $result;
 }
@@ -141,11 +142,12 @@ function serviceAccountCreds($stub, $args)
     $jsonKey = json_decode(
         file_get_contents(getenv(CredentialsLoader::ENV_VAR)),
         true);
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true);
-    hardAssert($result->getUsername() == $jsonKey['client_email'],
-             'invalid email returned');
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true);
+    hardAssert($result->getUsername() === $jsonKey['client_email'],
+               'invalid email returned');
     hardAssert(strpos($args['oauth_scope'], $result->getOauthScope()) !== false,
-             'invalid oauth scope returned');
+               'invalid oauth scope returned');
 }
 
 /**
@@ -163,9 +165,10 @@ function computeEngineCreds($stub, $args)
     if (!array_key_exists('default_service_account', $args)) {
         throw new Exception('Missing default_service_account');
     }
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true);
-    hardAssert($args['default_service_account'] == $result->getUsername(),
-             'invalid email returned');
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true);
+    hardAssert($args['default_service_account'] === $result->getUsername(),
+               'invalid email returned');
 }
 
 /**
@@ -179,9 +182,10 @@ function jwtTokenCreds($stub, $args)
     $jsonKey = json_decode(
         file_get_contents(getenv(CredentialsLoader::ENV_VAR)),
         true);
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true);
-    hardAssert($result->getUsername() == $jsonKey['client_email'],
-             'invalid email returned');
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true);
+    hardAssert($result->getUsername() === $jsonKey['client_email'],
+               'invalid email returned');
 }
 
 /**
@@ -195,9 +199,10 @@ function oauth2AuthToken($stub, $args)
     $jsonKey = json_decode(
         file_get_contents(getenv(CredentialsLoader::ENV_VAR)),
         true);
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true);
-    hardAssert($result->getUsername() == $jsonKey['client_email'],
-             'invalid email returned');
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true);
+    hardAssert($result->getUsername() === $jsonKey['client_email'],
+               'invalid email returned');
 }
 
 function updateAuthMetadataCallback($context)
@@ -209,8 +214,9 @@ function updateAuthMetadataCallback($context)
     $metadata = [];
     $result = $auth_credentials->updateMetadata([], $authUri);
     foreach ($result as $key => $value) {
-      $metadata[strtolower($key)] = $value;
+        $metadata[strtolower($key)] = $value;
     }
+
     return $metadata;
 }
 
@@ -226,10 +232,11 @@ function perRpcCreds($stub, $args)
         file_get_contents(getenv(CredentialsLoader::ENV_VAR)),
         true);
 
-    $result = performLargeUnary($stub, $fillUsername = true, $fillOauthScope = true,
+    $result = performLargeUnary($stub, $fillUsername = true,
+                                $fillOauthScope = true,
                                 'updateAuthMetadataCallback');
-    hardAssert($result->getUsername() == $jsonKey['client_email'],
-             'invalid email returned');
+    hardAssert($result->getUsername() === $jsonKey['client_email'],
+               'invalid email returned');
 }
 
 /**
@@ -258,7 +265,7 @@ function clientStreaming($stub)
     list($result, $status) = $call->wait();
     hardAssertIfStatusOk($status);
     hardAssert($result->getAggregatedPayloadSize() === 74922,
-              'aggregated_payload_size was incorrect');
+               'aggregated_payload_size was incorrect');
 }
 
 /**
@@ -283,10 +290,11 @@ function serverStreaming($stub)
     foreach ($call->responses() as $value) {
         hardAssert($i < 4, 'Too many responses');
         $payload = $value->getPayload();
-        hardAssert($payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
-                'Payload '.$i.' had the wrong type');
+        hardAssert(
+            $payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
+            'Payload '.$i.' had the wrong type');
         hardAssert(strlen($payload->getBody()) === $sizes[$i],
-                'Response '.$i.' had the wrong length');
+                   'Response '.$i.' had the wrong length');
         $i += 1;
     }
     hardAssertIfStatusOk($call->getStatus());
@@ -318,10 +326,11 @@ function pingPong($stub)
 
         hardAssert($response !== null, 'Server returned too few responses');
         $payload = $response->getPayload();
-        hardAssert($payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
-                'Payload '.$i.' had the wrong type');
+        hardAssert(
+            $payload->getType() === grpc\testing\PayloadType::COMPRESSABLE,
+            'Payload '.$i.' had the wrong type');
         hardAssert(strlen($payload->getBody()) === $response_lengths[$i],
-                'Payload '.$i.' had the wrong length');
+                   'Payload '.$i.' had the wrong length');
     }
     $call->writesDone();
     hardAssert($call->read() === null, 'Server returned too many responses');
@@ -352,7 +361,7 @@ function cancelAfterBegin($stub)
     $call->cancel();
     list($result, $status) = $call->wait();
     hardAssert($status->code === Grpc\STATUS_CANCELLED,
-             'Call status was not CANCELLED');
+               'Call status was not CANCELLED');
 }
 
 /**
@@ -377,7 +386,7 @@ function cancelAfterFirstResponse($stub)
 
     $call->cancel();
     hardAssert($call->getStatus()->code === Grpc\STATUS_CANCELLED,
-             'Call status was not CANCELLED');
+               'Call status was not CANCELLED');
 }
 
 function timeoutOnSleepingServer($stub)
@@ -396,7 +405,7 @@ function timeoutOnSleepingServer($stub)
     $response = $call->read();
 
     hardAssert($call->getStatus()->code === Grpc\STATUS_DEADLINE_EXCEEDED,
-             'Call status was not DEADLINE_EXCEEDED');
+               'Call status was not DEADLINE_EXCEEDED');
 }
 
 function customMetadata($stub)
@@ -425,9 +434,9 @@ function customMetadata($stub)
     $initial_metadata = $call->getMetadata();
     hardAssert(array_key_exists($ECHO_INITIAL_KEY, $initial_metadata),
                'Initial metadata does not contain expected key');
-    hardAssert($initial_metadata[$ECHO_INITIAL_KEY][0] ==
-               $ECHO_INITIAL_VALUE,
-               'Incorrect initial metadata value');
+    hardAssert(
+        $initial_metadata[$ECHO_INITIAL_KEY][0] === $ECHO_INITIAL_VALUE,
+        'Incorrect initial metadata value');
 
     list($result, $status) = $call->wait();
     hardAssertIfStatusOk($status);
@@ -435,8 +444,9 @@ function customMetadata($stub)
     $trailing_metadata = $call->getTrailingMetadata();
     hardAssert(array_key_exists($ECHO_TRAILING_KEY, $trailing_metadata),
                'Trailing metadata does not contain expected key');
-    hardAssert($trailing_metadata[$ECHO_TRAILING_KEY][0] ==
-               $ECHO_TRAILING_VALUE, 'Incorrect trailing metadata value');
+    hardAssert(
+        $trailing_metadata[$ECHO_TRAILING_KEY][0] === $ECHO_TRAILING_VALUE,
+        'Incorrect trailing metadata value');
 
     $streaming_call = $stub->FullDuplexCall($metadata);
 
@@ -451,7 +461,7 @@ function customMetadata($stub)
     hardAssert(array_key_exists($ECHO_TRAILING_KEY,
                                 $streaming_trailing_metadata),
                'Trailing metadata does not contain expected key');
-    hardAssert($streaming_trailing_metadata[$ECHO_TRAILING_KEY][0] ==
+    hardAssert($streaming_trailing_metadata[$ECHO_TRAILING_KEY][0] ===
                $ECHO_TRAILING_VALUE, 'Incorrect trailing metadata value');
 }
 
@@ -506,7 +516,7 @@ function _makeStub($args)
         throw new Exception('Missing argument: --test_case is required');
     }
 
-    if ($args['server_port'] == 443) {
+    if ($args['server_port'] === 443) {
         $server_address = $args['server_host'];
     } else {
         $server_address = $args['server_host'].':'.$args['server_port'];
@@ -548,7 +558,7 @@ function _makeStub($args)
 
     if (in_array($test_case, ['service_account_creds',
                               'compute_engine_creds', 'jwt_token_creds', ])) {
-        if ($test_case == 'jwt_token_creds') {
+        if ($test_case === 'jwt_token_creds') {
             $auth_credentials = ApplicationDefaultCredentials::getCredentials();
         } else {
             $auth_credentials = ApplicationDefaultCredentials::getCredentials(
@@ -558,7 +568,7 @@ function _makeStub($args)
         $opts['update_metadata'] = $auth_credentials->getUpdateMetadataFunc();
     }
 
-    if ($test_case == 'oauth2_auth_token') {
+    if ($test_case === 'oauth2_auth_token') {
         $auth_credentials = ApplicationDefaultCredentials::getCredentials(
             $args['oauth_scope']
         );
@@ -578,8 +588,9 @@ function _makeStub($args)
         $opts['update_metadata'] = $update_metadata;
     }
 
-    if ($test_case == 'unimplemented_method') {
-        $stub = new grpc\testing\UnimplementedServiceClient($server_address, $opts);
+    if ($test_case === 'unimplemented_method') {
+        $stub = new grpc\testing\UnimplementedServiceClient($server_address,
+                                                            $opts);
     } else {
         $stub = new grpc\testing\TestServiceClient($server_address, $opts);
     }
@@ -656,7 +667,8 @@ function interop_main($args, $stub = false)
     return $stub;
 }
 
-if (isset($_SERVER['PHP_SELF']) && preg_match('/interop_client/', $_SERVER['PHP_SELF'])) {
+if (isset($_SERVER['PHP_SELF']) &&
+    preg_match('/interop_client/', $_SERVER['PHP_SELF'])) {
     $args = getopt('', ['server_host:', 'server_port:', 'test_case:',
                         'use_tls::', 'use_test_ca::',
                         'server_host_override:', 'oauth_scope:',
diff --git a/src/php/tests/unit_tests/CallCredentials2Test.php b/src/php/tests/unit_tests/CallCredentials2Test.php
index b3b98a22ca..fa31439c54 100644
--- a/src/php/tests/unit_tests/CallCredentials2Test.php
+++ b/src/php/tests/unit_tests/CallCredentials2Test.php
@@ -170,7 +170,7 @@ class CallCredentials2Test extends PHPUnit_Framework_TestCase
         $this->assertTrue(is_string($context->service_url));
         $this->assertTrue(is_string($context->method_name));
 
-        return "a string";
+        return 'a string';
     }
 
     public function testCallbackWithInvalidReturnValue()
@@ -196,5 +196,4 @@ class CallCredentials2Test extends PHPUnit_Framework_TestCase
         $this->assertTrue($event->send_close);
         $this->assertTrue($event->status->code == Grpc\STATUS_UNAUTHENTICATED);
     }
-
 }
diff --git a/src/python/grpcio/grpc/__init__.py b/src/python/grpcio/grpc/__init__.py
index faf3ab5f0d..b9b662c032 100644
--- a/src/python/grpcio/grpc/__init__.py
+++ b/src/python/grpcio/grpc/__init__.py
@@ -1189,7 +1189,7 @@ def insecure_channel(target, options=None):
     A Channel to the target through which RPCs may be conducted.
   """
   from grpc import _channel
-  return _channel.Channel(target, options, None)
+  return _channel.Channel(target, () if options is None else options, None)
 
 
 def secure_channel(target, credentials, options=None):
@@ -1205,10 +1205,11 @@ def secure_channel(target, credentials, options=None):
     A Channel to the target through which RPCs may be conducted.
   """
   from grpc import _channel
-  return _channel.Channel(target, options, credentials._credentials)
+  return _channel.Channel(target, () if options is None else options,
+                          credentials._credentials)
 
 
-def server(thread_pool, handlers=None):
+def server(thread_pool, handlers=None, options=None):
   """Creates a Server with which RPCs can be serviced.
 
   Args:
@@ -1219,12 +1220,15 @@ def server(thread_pool, handlers=None):
       only handlers the server will use to service RPCs; other handlers may
       later be added by calling add_generic_rpc_handlers any time before the
       returned Server is started.
+    options: A sequence of string-value pairs according to which to configure
+      the created server.
 
   Returns:
     A Server with which RPCs can be serviced.
   """
   from grpc import _server
-  return _server.Server(thread_pool, () if handlers is None else handlers)
+  return _server.Server(thread_pool, () if handlers is None else handlers,
+                        () if options is None else options)
 
 
 ###################################  __all__  #################################
diff --git a/src/python/grpcio/grpc/_channel.py b/src/python/grpcio/grpc/_channel.py
index 3117dd1cb3..53a26727ab 100644
--- a/src/python/grpcio/grpc/_channel.py
+++ b/src/python/grpcio/grpc/_channel.py
@@ -842,18 +842,8 @@ def _unsubscribe(state, callback):
 
 
 def _options(options):
-  if options is None:
-    pairs = ((cygrpc.ChannelArgKey.primary_user_agent_string, _USER_AGENT),)
-  else:
-    pairs = list(options) + [
-        (cygrpc.ChannelArgKey.primary_user_agent_string, _USER_AGENT)]
-  encoded_pairs = [
-      (_common.encode(arg_name), arg_value) if isinstance(arg_value, int)
-      else (_common.encode(arg_name), _common.encode(arg_value))
-      for arg_name, arg_value in pairs]
-  return cygrpc.ChannelArgs([
-      cygrpc.ChannelArg(arg_name, arg_value)
-      for arg_name, arg_value in encoded_pairs])
+  return list(options) + [
+      (cygrpc.ChannelArgKey.primary_user_agent_string, _USER_AGENT)]
 
 
 class Channel(grpc.Channel):
@@ -867,7 +857,8 @@ class Channel(grpc.Channel):
       credentials: A cygrpc.ChannelCredentials or None.
     """
     self._channel = cygrpc.Channel(
-        _common.encode(target), _options(options), credentials)
+        _common.encode(target), _common.channel_args(_options(options)),
+        credentials)
     self._call_state = _ChannelCallState(self._channel)
     self._connectivity_state = _ChannelConnectivityState(self._channel)
 
diff --git a/src/python/grpcio/grpc/_common.py b/src/python/grpcio/grpc/_common.py
index 4d7d521419..cc0984c8c6 100644
--- a/src/python/grpcio/grpc/_common.py
+++ b/src/python/grpcio/grpc/_common.py
@@ -94,6 +94,16 @@ def decode(b):
       return b.decode('latin1')
 
 
+def channel_args(options):
+  channel_args = []
+  for key, value in options:
+    if isinstance(value, six.string_types):
+      channel_args.append(cygrpc.ChannelArg(encode(key), encode(value)))
+    else:
+      channel_args.append(cygrpc.ChannelArg(encode(key), value))
+  return cygrpc.ChannelArgs(channel_args)
+
+
 def cygrpc_metadata(application_metadata):
   return _EMPTY_METADATA if application_metadata is None else cygrpc.Metadata(
       cygrpc.Metadatum(encode(key), encode(value))
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi
index 3df937eb14..73d1ff7b97 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/channel.pyx.pxi
@@ -32,15 +32,16 @@ cimport cpython
 
 cdef class Channel:
 
-  def __cinit__(self, bytes target, ChannelArgs arguments=None,
+  def __cinit__(self, bytes target, ChannelArgs arguments,
                 ChannelCredentials channel_credentials=None):
     grpc_init()
     cdef grpc_channel_args *c_arguments = NULL
     cdef char *c_target = NULL
     self.c_channel = NULL
     self.references = []
-    if arguments is not None:
+    if len(arguments) > 0:
       c_arguments = &arguments.c_args
+      self.references.append(arguments)
     c_target = target
     if channel_credentials is None:
       with nogil:
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi
index ca2b831114..18db38b686 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/server.pyx.pxi
@@ -34,12 +34,12 @@ import time
 
 cdef class Server:
 
-  def __cinit__(self, ChannelArgs arguments=None):
+  def __cinit__(self, ChannelArgs arguments):
     grpc_init()
     cdef grpc_channel_args *c_arguments = NULL
     self.references = []
     self.registered_completion_queues = []
-    if arguments is not None:
+    if len(arguments) > 0:
       c_arguments = &arguments.c_args
       self.references.append(arguments)
     with nogil:
diff --git a/src/python/grpcio/grpc/_server.py b/src/python/grpcio/grpc/_server.py
index 94a13bfb2f..5f846ce773 100644
--- a/src/python/grpcio/grpc/_server.py
+++ b/src/python/grpcio/grpc/_server.py
@@ -728,12 +728,11 @@ def _start(state):
         cleanup_server, target=_serve, args=(state,))
     thread.start()
 
-
 class Server(grpc.Server):
 
-  def __init__(self, thread_pool, generic_handlers):
+  def __init__(self, thread_pool, generic_handlers, options):
     completion_queue = cygrpc.CompletionQueue()
-    server = cygrpc.Server()
+    server = cygrpc.Server(_common.channel_args(options))
     server.register_completion_queue(completion_queue)
     self._state = _ServerState(
         completion_queue, server, generic_handlers, thread_pool)
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 137177774b..ef9e85ccfb 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -268,6 +268,7 @@ CORE_SOURCE_FILES = [
   'src/core/ext/census/operation.c',
   'src/core/ext/census/placeholders.c',
   'src/core/ext/census/resource.c',
+  'src/core/ext/census/trace_context.c',
   'src/core/ext/census/tracing.c',
   'src/core/plugin_registry/grpc_plugin_registry.c',
   'src/boringssl/err_data.c',
diff --git a/src/python/grpcio_tests/tests/tests.json b/src/python/grpcio_tests/tests/tests.json
index dcaef0db1f..2071a33e13 100644
--- a/src/python/grpcio_tests/tests/tests.json
+++ b/src/python/grpcio_tests/tests/tests.json
@@ -7,6 +7,7 @@
   "_beta_features_test.BetaFeaturesTest", 
   "_beta_features_test.ContextManagementAndLifecycleTest", 
   "_cancel_many_calls_test.CancelManyCallsTest",
+  "_channel_args_test.ChannelArgsTest",
   "_channel_connectivity_test.ChannelConnectivityTest",
   "_channel_ready_future_test.ChannelReadyFutureTest",
   "_channel_test.ChannelTest", 
diff --git a/src/python/grpcio_tests/tests/unit/_channel_args_test.py b/src/python/grpcio_tests/tests/unit/_channel_args_test.py
new file mode 100644
index 0000000000..6a636d7993
--- /dev/null
+++ b/src/python/grpcio_tests/tests/unit/_channel_args_test.py
@@ -0,0 +1,53 @@
+# 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 of Channel Args on client/server side."""
+
+import unittest
+
+import grpc
+
+TEST_CHANNEL_ARGS = (
+    ('arg1', b'bytes_val'),
+    ('arg2', 'str_val'),
+    ('arg3', 1),
+    (b'arg4', 'str_val'),
+)
+
+
+class ChannelArgsTest(unittest.TestCase):
+
+  def test_client(self):
+    grpc.insecure_channel('localhost:8080', options=TEST_CHANNEL_ARGS)
+
+  def test_server(self):
+    grpc.server(None, options=TEST_CHANNEL_ARGS)
+
+if __name__ == '__main__':
+  unittest.main(verbosity=2)
diff --git a/src/python/grpcio_tests/tests/unit/_channel_connectivity_test.py b/src/python/grpcio_tests/tests/unit/_channel_connectivity_test.py
index 9cae96a00d..1324ad37b6 100644
--- a/src/python/grpcio_tests/tests/unit/_channel_connectivity_test.py
+++ b/src/python/grpcio_tests/tests/unit/_channel_connectivity_test.py
@@ -78,7 +78,7 @@ class ChannelConnectivityTest(unittest.TestCase):
   def test_lonely_channel_connectivity(self):
     callback = _Callback()
 
-    channel = _channel.Channel('localhost:12345', None, None)
+    channel = _channel.Channel('localhost:12345', (), None)
     channel.subscribe(callback.update, try_to_connect=False)
     first_connectivities = callback.block_until_connectivities_satisfy(bool)
     channel.subscribe(callback.update, try_to_connect=True)
@@ -105,13 +105,13 @@ class ChannelConnectivityTest(unittest.TestCase):
 
   def test_immediately_connectable_channel_connectivity(self):
     thread_pool = _thread_pool.RecordingThreadPool(max_workers=None)
-    server = _server.Server(thread_pool, ())
+    server = _server.Server(thread_pool, (), ())
     port = server.add_insecure_port('[::]:0')
     server.start()
     first_callback = _Callback()
     second_callback = _Callback()
 
-    channel = _channel.Channel('localhost:{}'.format(port), None, None)
+    channel = _channel.Channel('localhost:{}'.format(port), (), None)
     channel.subscribe(first_callback.update, try_to_connect=False)
     first_connectivities = first_callback.block_until_connectivities_satisfy(
         bool)
@@ -146,12 +146,12 @@ class ChannelConnectivityTest(unittest.TestCase):
 
   def test_reachable_then_unreachable_channel_connectivity(self):
     thread_pool = _thread_pool.RecordingThreadPool(max_workers=None)
-    server = _server.Server(thread_pool, ())
+    server = _server.Server(thread_pool, (), ())
     port = server.add_insecure_port('[::]:0')
     server.start()
     callback = _Callback()
 
-    channel = _channel.Channel('localhost:{}'.format(port), None, None)
+    channel = _channel.Channel('localhost:{}'.format(port), (), None)
     channel.subscribe(callback.update, try_to_connect=True)
     callback.block_until_connectivities_satisfy(_ready_in_connectivities)
     # Now take down the server and confirm that channel readiness is repudiated.
diff --git a/src/python/grpcio_tests/tests/unit/_channel_ready_future_test.py b/src/python/grpcio_tests/tests/unit/_channel_ready_future_test.py
index 24f5b45b18..60d478bcd9 100644
--- a/src/python/grpcio_tests/tests/unit/_channel_ready_future_test.py
+++ b/src/python/grpcio_tests/tests/unit/_channel_ready_future_test.py
@@ -79,7 +79,7 @@ class ChannelReadyFutureTest(unittest.TestCase):
 
   def test_immediately_connectable_channel_connectivity(self):
     thread_pool = _thread_pool.RecordingThreadPool(max_workers=None)
-    server = _server.Server(thread_pool, ())
+    server = _server.Server(thread_pool, (), ())
     port = server.add_insecure_port('[::]:0')
     server.start()
     channel = grpc.insecure_channel('localhost:{}'.format(port))
diff --git a/src/python/grpcio_tests/tests/unit/_cython/_cancel_many_calls_test.py b/src/python/grpcio_tests/tests/unit/_cython/_cancel_many_calls_test.py
index cf212c5653..20115fb22c 100644
--- a/src/python/grpcio_tests/tests/unit/_cython/_cancel_many_calls_test.py
+++ b/src/python/grpcio_tests/tests/unit/_cython/_cancel_many_calls_test.py
@@ -157,11 +157,12 @@ class CancelManyCallsTest(unittest.TestCase):
     server_thread_pool = logging_pool.pool(test_constants.THREAD_CONCURRENCY)
 
     server_completion_queue = cygrpc.CompletionQueue()
-    server = cygrpc.Server()
+    server = cygrpc.Server(cygrpc.ChannelArgs([]))
     server.register_completion_queue(server_completion_queue)
     port = server.add_http2_port(b'[::]:0')
     server.start()
-    channel = cygrpc.Channel('localhost:{}'.format(port).encode())
+    channel = cygrpc.Channel('localhost:{}'.format(port).encode(),
+                             cygrpc.ChannelArgs([]))
 
     state = _State()
 
diff --git a/src/python/grpcio_tests/tests/unit/_cython/_read_some_but_not_all_responses_test.py b/src/python/grpcio_tests/tests/unit/_cython/_read_some_but_not_all_responses_test.py
index 152d8edde3..2ae5285232 100644
--- a/src/python/grpcio_tests/tests/unit/_cython/_read_some_but_not_all_responses_test.py
+++ b/src/python/grpcio_tests/tests/unit/_cython/_read_some_but_not_all_responses_test.py
@@ -124,11 +124,12 @@ class ReadSomeButNotAllResponsesTest(unittest.TestCase):
 
   def testReadSomeButNotAllResponses(self):
     server_completion_queue = cygrpc.CompletionQueue()
-    server = cygrpc.Server()
+    server = cygrpc.Server(cygrpc.ChannelArgs([]))
     server.register_completion_queue(server_completion_queue)
     port = server.add_http2_port(b'[::]:0')
     server.start()
-    channel = cygrpc.Channel('localhost:{}'.format(port).encode())
+    channel = cygrpc.Channel('localhost:{}'.format(port).encode(),
+                             cygrpc.ChannelArgs([]))
 
     server_shutdown_tag = 'server_shutdown_tag'
     server_driver = _ServerDriver(server_completion_queue, server_shutdown_tag)
diff --git a/src/python/grpcio_tests/tests/unit/_cython/cygrpc_test.py b/src/python/grpcio_tests/tests/unit/_cython/cygrpc_test.py
index 142387d810..8dedebfabe 100644
--- a/src/python/grpcio_tests/tests/unit/_cython/cygrpc_test.py
+++ b/src/python/grpcio_tests/tests/unit/_cython/cygrpc_test.py
@@ -121,7 +121,7 @@ class TypeSmokeTest(unittest.TestCase):
     del call_credentials
 
   def testServerStartNoExplicitShutdown(self):
-    server = cygrpc.Server()
+    server = cygrpc.Server(cygrpc.ChannelArgs([]))
     completion_queue = cygrpc.CompletionQueue()
     server.register_completion_queue(completion_queue)
     port = server.add_http2_port(b'[::]:0')
@@ -131,7 +131,7 @@ class TypeSmokeTest(unittest.TestCase):
 
   def testServerStartShutdown(self):
     completion_queue = cygrpc.CompletionQueue()
-    server = cygrpc.Server()
+    server = cygrpc.Server(cygrpc.ChannelArgs([]))
     server.add_http2_port(b'[::]:0')
     server.register_completion_queue(completion_queue)
     server.start()
@@ -148,7 +148,7 @@ class ServerClientMixin(object):
 
   def setUpMixin(self, server_credentials, client_credentials, host_override):
     self.server_completion_queue = cygrpc.CompletionQueue()
-    self.server = cygrpc.Server()
+    self.server = cygrpc.Server(cygrpc.ChannelArgs([]))
     self.server.register_completion_queue(self.server_completion_queue)
     if server_credentials:
       self.port = self.server.add_http2_port(b'[::]:0', server_credentials)
@@ -164,7 +164,8 @@ class ServerClientMixin(object):
           'localhost:{}'.format(self.port).encode(), client_channel_arguments,
           client_credentials)
     else:
-      self.client_channel = cygrpc.Channel('localhost:{}'.format(self.port).encode())
+      self.client_channel = cygrpc.Channel(
+          'localhost:{}'.format(self.port).encode(), cygrpc.ChannelArgs([]))
     if host_override:
       self.host_argument = None  # default host
       self.expected_host = host_override