Merge github.com:grpc/grpc into filter-selection

24 files changed, 625 insertions, 70 deletions

diff --git a/BUILD b/BUILD
index 571226bc5b..514aea8f53 100644
--- a/BUILD
+++ b/BUILD
@@ -45,6 +45,7 @@ cc_library(
   name = "gpr",
   srcs = [
     "src/core/profiling/timers.h",
+    "src/core/support/backoff.h",
     "src/core/support/block_annotate.h",
     "src/core/support/env.h",
     "src/core/support/load_file.h",
@@ -59,6 +60,7 @@ cc_library(
     "src/core/profiling/stap_timers.c",
     "src/core/support/alloc.c",
     "src/core/support/avl.c",
+    "src/core/support/backoff.c",
     "src/core/support/cmdline.c",
     "src/core/support/cpu_iphone.c",
     "src/core/support/cpu_linux.c",
@@ -1249,6 +1251,7 @@ objc_library(
     "src/core/profiling/stap_timers.c",
     "src/core/support/alloc.c",
     "src/core/support/avl.c",
+    "src/core/support/backoff.c",
     "src/core/support/cmdline.c",
     "src/core/support/cpu_iphone.c",
     "src/core/support/cpu_linux.c",
@@ -1333,6 +1336,7 @@ objc_library(
     "include/grpc/impl/codegen/sync_win32.h",
     "include/grpc/impl/codegen/time.h",
     "src/core/profiling/timers.h",
+    "src/core/support/backoff.h",
     "src/core/support/block_annotate.h",
     "src/core/support/env.h",
     "src/core/support/load_file.h",
diff --git a/INSTALL.md b/INSTALL.md
index 454a8b7b2f..66e6c33a77 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -52,6 +52,6 @@ gRPC C Core library.
  $ git clone https://github.com/grpc/grpc.git
  $ cd grpc
  $ git submodule update --init
- $ make 
+ $ make
  $ [sudo] make install
 ```
diff --git a/Makefile b/Makefile
index 273193e78d..3843aff810 100644
--- a/Makefile
+++ b/Makefile
@@ -893,6 +893,7 @@ fling_test: $(BINDIR)/$(CONFIG)/fling_test
 gen_hpack_tables: $(BINDIR)/$(CONFIG)/gen_hpack_tables
 gen_legal_metadata_characters: $(BINDIR)/$(CONFIG)/gen_legal_metadata_characters
 gpr_avl_test: $(BINDIR)/$(CONFIG)/gpr_avl_test
+gpr_backoff_test: $(BINDIR)/$(CONFIG)/gpr_backoff_test
 gpr_cmdline_test: $(BINDIR)/$(CONFIG)/gpr_cmdline_test
 gpr_cpu_test: $(BINDIR)/$(CONFIG)/gpr_cpu_test
 gpr_env_test: $(BINDIR)/$(CONFIG)/gpr_env_test
@@ -1206,6 +1207,7 @@ buildtests_c: privatelibs_c \
   $(BINDIR)/$(CONFIG)/fling_stream_test \
   $(BINDIR)/$(CONFIG)/fling_test \
   $(BINDIR)/$(CONFIG)/gpr_avl_test \
+  $(BINDIR)/$(CONFIG)/gpr_backoff_test \
   $(BINDIR)/$(CONFIG)/gpr_cmdline_test \
   $(BINDIR)/$(CONFIG)/gpr_cpu_test \
   $(BINDIR)/$(CONFIG)/gpr_env_test \
@@ -1462,6 +1464,8 @@ test_c: buildtests_c
 	$(Q) $(BINDIR)/$(CONFIG)/fling_test || ( echo test fling_test failed ; exit 1 )
 	$(E) "[RUN]     Testing gpr_avl_test"
 	$(Q) $(BINDIR)/$(CONFIG)/gpr_avl_test || ( echo test gpr_avl_test failed ; exit 1 )
+	$(E) "[RUN]     Testing gpr_backoff_test"
+	$(Q) $(BINDIR)/$(CONFIG)/gpr_backoff_test || ( echo test gpr_backoff_test failed ; exit 1 )
 	$(E) "[RUN]     Testing gpr_cmdline_test"
 	$(Q) $(BINDIR)/$(CONFIG)/gpr_cmdline_test || ( echo test gpr_cmdline_test failed ; exit 1 )
 	$(E) "[RUN]     Testing gpr_cpu_test"
@@ -2254,6 +2258,7 @@ LIBGPR_SRC = \
     src/core/profiling/stap_timers.c \
     src/core/support/alloc.c \
     src/core/support/avl.c \
+    src/core/support/backoff.c \
     src/core/support/cmdline.c \
     src/core/support/cpu_iphone.c \
     src/core/support/cpu_linux.c \
@@ -6629,6 +6634,38 @@ endif
 endif
 
 
+GPR_BACKOFF_TEST_SRC = \
+    test/core/support/backoff_test.c \
+
+GPR_BACKOFF_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(GPR_BACKOFF_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/gpr_backoff_test: openssl_dep_error
+
+else
+
+
+
+$(BINDIR)/$(CONFIG)/gpr_backoff_test: $(GPR_BACKOFF_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LD) $(LDFLAGS) $(GPR_BACKOFF_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LDLIBS) $(LDLIBS_SECURE) -o $(BINDIR)/$(CONFIG)/gpr_backoff_test
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/support/backoff_test.o:  $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
+
+deps_gpr_backoff_test: $(GPR_BACKOFF_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(GPR_BACKOFF_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
 GPR_CMDLINE_TEST_SRC = \
     test/core/support/cmdline_test.c \
 
diff --git a/binding.gyp b/binding.gyp
index 25ad6e28af..5f9dfd9c6d 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -496,6 +496,7 @@
         'src/core/profiling/stap_timers.c',
         'src/core/support/alloc.c',
         'src/core/support/avl.c',
+        'src/core/support/backoff.c',
         'src/core/support/cmdline.c',
         'src/core/support/cpu_iphone.c',
         'src/core/support/cpu_linux.c',
diff --git a/build.yaml b/build.yaml
index b95232b929..3e10d02c7e 100644
--- a/build.yaml
+++ b/build.yaml
@@ -55,6 +55,7 @@ filegroups:
   - include/grpc/support/useful.h
   headers:
   - src/core/profiling/timers.h
+  - src/core/support/backoff.h
   - src/core/support/block_annotate.h
   - src/core/support/env.h
   - src/core/support/load_file.h
@@ -70,6 +71,7 @@ filegroups:
   - src/core/profiling/stap_timers.c
   - src/core/support/alloc.c
   - src/core/support/avl.c
+  - src/core/support/backoff.c
   - src/core/support/cmdline.c
   - src/core/support/cpu_iphone.c
   - src/core/support/cpu_linux.c
@@ -1245,6 +1247,14 @@ targets:
   deps:
   - gpr_test_util
   - gpr
+- name: gpr_backoff_test
+  build: test
+  language: c
+  src:
+  - test/core/support/backoff_test.c
+  deps:
+  - gpr_test_util
+  - gpr
 - name: gpr_cmdline_test
   build: test
   language: c
@@ -2444,7 +2454,7 @@ targets:
   - linux
   - posix
 - name: qps_openloop_test
-  cpu_cost: 10
+  cpu_cost: 0.5
   build: test
   language: c++
   src:
diff --git a/config.m4 b/config.m4
index f65fe76352..91b87e2448 100644
--- a/config.m4
+++ b/config.m4
@@ -40,6 +40,7 @@ if test "$PHP_GRPC" != "no"; then
     src/core/profiling/stap_timers.c \
     src/core/support/alloc.c \
     src/core/support/avl.c \
+    src/core/support/backoff.c \
     src/core/support/cmdline.c \
     src/core/support/cpu_iphone.c \
     src/core/support/cpu_linux.c \
diff --git a/gRPC.podspec b/gRPC.podspec
index e133617dd8..86121c9d28 100644
--- a/gRPC.podspec
+++ b/gRPC.podspec
@@ -64,6 +64,7 @@ Pod::Spec.new do |s|
   # Core cross-platform gRPC library, written in C.
   s.subspec 'C-Core' do |ss|
     ss.source_files = 'src/core/profiling/timers.h',
+                      'src/core/support/backoff.h',
                       'src/core/support/block_annotate.h',
                       'src/core/support/env.h',
                       'src/core/support/load_file.h',
@@ -120,6 +121,7 @@ Pod::Spec.new do |s|
                       'src/core/profiling/stap_timers.c',
                       'src/core/support/alloc.c',
                       'src/core/support/avl.c',
+                      'src/core/support/backoff.c',
                       'src/core/support/cmdline.c',
                       'src/core/support/cpu_iphone.c',
                       'src/core/support/cpu_linux.c',
@@ -478,6 +480,7 @@ Pod::Spec.new do |s|
                       'third_party/nanopb/pb_encode.c'
 
     ss.private_header_files = 'src/core/profiling/timers.h',
+                              'src/core/support/backoff.h',
                               'src/core/support/block_annotate.h',
                               'src/core/support/env.h',
                               'src/core/support/load_file.h',
diff --git a/grpc.gemspec b/grpc.gemspec
index 7a5562ede8..c06262212d 100755
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -89,6 +89,7 @@ Gem::Specification.new do |s|
   s.files += %w( include/grpc/impl/codegen/sync_win32.h )
   s.files += %w( include/grpc/impl/codegen/time.h )
   s.files += %w( src/core/profiling/timers.h )
+  s.files += %w( src/core/support/backoff.h )
   s.files += %w( src/core/support/block_annotate.h )
   s.files += %w( src/core/support/env.h )
   s.files += %w( src/core/support/load_file.h )
@@ -103,6 +104,7 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/profiling/stap_timers.c )
   s.files += %w( src/core/support/alloc.c )
   s.files += %w( src/core/support/avl.c )
+  s.files += %w( src/core/support/backoff.c )
   s.files += %w( src/core/support/cmdline.c )
   s.files += %w( src/core/support/cpu_iphone.c )
   s.files += %w( src/core/support/cpu_linux.c )
diff --git a/package.json b/package.json
index dd976f2ae0..371dfdce99 100644
--- a/package.json
+++ b/package.json
@@ -873,6 +873,7 @@
     "include/grpc/impl/codegen/sync_win32.h",
     "include/grpc/impl/codegen/time.h",
     "src/core/profiling/timers.h",
+    "src/core/support/backoff.h",
     "src/core/support/block_annotate.h",
     "src/core/support/env.h",
     "src/core/support/load_file.h",
@@ -887,6 +888,7 @@
     "src/core/profiling/stap_timers.c",
     "src/core/support/alloc.c",
     "src/core/support/avl.c",
+    "src/core/support/backoff.c",
     "src/core/support/cmdline.c",
     "src/core/support/cpu_iphone.c",
     "src/core/support/cpu_linux.c",
diff --git a/package.xml b/package.xml
index 7afb8d5dfa..a0d8bfd885 100644
--- a/package.xml
+++ b/package.xml
@@ -93,6 +93,7 @@
     <file baseinstalldir="/" name="include/grpc/impl/codegen/sync_win32.h" role="src" />
     <file baseinstalldir="/" name="include/grpc/impl/codegen/time.h" role="src" />
     <file baseinstalldir="/" name="src/core/profiling/timers.h" role="src" />
+    <file baseinstalldir="/" name="src/core/support/backoff.h" role="src" />
     <file baseinstalldir="/" name="src/core/support/block_annotate.h" role="src" />
     <file baseinstalldir="/" name="src/core/support/env.h" role="src" />
     <file baseinstalldir="/" name="src/core/support/load_file.h" role="src" />
@@ -107,6 +108,7 @@
     <file baseinstalldir="/" name="src/core/profiling/stap_timers.c" role="src" />
     <file baseinstalldir="/" name="src/core/support/alloc.c" role="src" />
     <file baseinstalldir="/" name="src/core/support/avl.c" role="src" />
+    <file baseinstalldir="/" name="src/core/support/backoff.c" role="src" />
     <file baseinstalldir="/" name="src/core/support/cmdline.c" role="src" />
     <file baseinstalldir="/" name="src/core/support/cpu_iphone.c" role="src" />
     <file baseinstalldir="/" name="src/core/support/cpu_linux.c" role="src" />
diff --git a/src/core/client_config/subchannel.c b/src/core/client_config/subchannel.c
index de28437d0c..8f150a8d81 100644
--- a/src/core/client_config/subchannel.c
+++ b/src/core/client_config/subchannel.c
@@ -45,6 +45,7 @@
 #include "src/core/client_config/subchannel_index.h"
 #include "src/core/iomgr/timer.h"
 #include "src/core/profiling/timers.h"
+#include "src/core/support/backoff.h"
 #include "src/core/surface/channel.h"
 #include "src/core/surface/channel_init.h"
 #include "src/core/transport/connectivity_state.h"
@@ -128,8 +129,8 @@ struct grpc_subchannel {
 
   /** next connect attempt time */
   gpr_timespec next_attempt;
-  /** amount to backoff each failure */
-  gpr_timespec backoff_delta;
+  /** backoff state */
+  gpr_backoff backoff_state;
   /** do we have an active alarm? */
   int have_alarm;
   /** our alarm */
@@ -147,7 +148,6 @@ struct grpc_subchannel_call {
 #define CALLSTACK_TO_SUBCHANNEL_CALL(callstack) \
   (((grpc_subchannel_call *)(callstack)) - 1)
 
-static gpr_timespec compute_connect_deadline(grpc_subchannel *c);
 static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *subchannel,
                                  bool iomgr_success);
 
@@ -338,6 +338,22 @@ grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
   grpc_closure_init(&c->connected, subchannel_connected, c);
   grpc_connectivity_state_init(&c->state_tracker, GRPC_CHANNEL_IDLE,
                                "subchannel");
+  gpr_backoff_init(&c->backoff_state,
+                   GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER,
+                   GRPC_SUBCHANNEL_RECONNECT_JITTER,
+                   GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS * 1000,
+                   GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
+  if (c->args) {
+    for (size_t i = 0; i < c->args->num_args; i++) {
+      if (0 == strcmp(c->args->args[i].key,
+                      "grpc.testing.fixed_reconnect_backoff")) {
+        GPR_ASSERT(c->args->args[i].type == GRPC_ARG_INTEGER);
+        gpr_backoff_init(&c->backoff_state, 1.0, 0.0,
+                         c->args->args[i].value.integer,
+                         c->args->args[i].value.integer);
+      }
+    }
+  }
   gpr_mu_init(&c->mu);
 
   return grpc_subchannel_index_register(exec_ctx, key, c);
@@ -349,7 +365,7 @@ static void continue_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   args.interested_parties = c->pollset_set;
   args.addr = c->addr;
   args.addr_len = c->addr_len;
-  args.deadline = compute_connect_deadline(c);
+  args.deadline = c->next_attempt;
   args.channel_args = c->args;
   args.initial_connect_string = c->initial_connect_string;
 
@@ -360,10 +376,8 @@ static void continue_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
 }
 
 static void start_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
-  c->backoff_delta = gpr_time_from_seconds(
-      GRPC_SUBCHANNEL_INITIAL_CONNECT_BACKOFF_SECONDS, GPR_TIMESPAN);
   c->next_attempt =
-      gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC), c->backoff_delta);
+      gpr_backoff_begin(&c->backoff_state, gpr_now(GPR_CLOCK_MONOTONIC));
   continue_connect(exec_ctx, c);
 }
 
@@ -557,50 +571,6 @@ static void publish_transport_locked(grpc_exec_ctx *exec_ctx,
                               "connected");
 }
 
-/* Generate a random number between 0 and 1. */
-static double generate_uniform_random_number(grpc_subchannel *c) {
-  c->random = (1103515245 * c->random + 12345) % ((uint32_t)1 << 31);
-  return c->random / (double)((uint32_t)1 << 31);
-}
-
-/* Update backoff_delta and next_attempt in subchannel */
-static void update_reconnect_parameters(grpc_subchannel *c) {
-  size_t i;
-  int32_t backoff_delta_millis, jitter;
-  int32_t max_backoff_millis =
-      GRPC_SUBCHANNEL_RECONNECT_MAX_BACKOFF_SECONDS * 1000;
-  double jitter_range;
-
-  if (c->args) {
-    for (i = 0; i < c->args->num_args; i++) {
-      if (0 == strcmp(c->args->args[i].key,
-                      "grpc.testing.fixed_reconnect_backoff")) {
-        GPR_ASSERT(c->args->args[i].type == GRPC_ARG_INTEGER);
-        c->next_attempt = gpr_time_add(
-            gpr_now(GPR_CLOCK_MONOTONIC),
-            gpr_time_from_millis(c->args->args[i].value.integer, GPR_TIMESPAN));
-        return;
-      }
-    }
-  }
-
-  backoff_delta_millis =
-      (int32_t)(gpr_time_to_millis(c->backoff_delta) *
-                GRPC_SUBCHANNEL_RECONNECT_BACKOFF_MULTIPLIER);
-  if (backoff_delta_millis > max_backoff_millis) {
-    backoff_delta_millis = max_backoff_millis;
-  }
-  c->backoff_delta = gpr_time_from_millis(backoff_delta_millis, GPR_TIMESPAN);
-  c->next_attempt =
-      gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC), c->backoff_delta);
-
-  jitter_range = GRPC_SUBCHANNEL_RECONNECT_JITTER * backoff_delta_millis;
-  jitter =
-      (int32_t)((2 * generate_uniform_random_number(c) - 1) * jitter_range);
-  c->next_attempt =
-      gpr_time_add(c->next_attempt, gpr_time_from_millis(jitter, GPR_TIMESPAN));
-}
-
 static void on_alarm(grpc_exec_ctx *exec_ctx, void *arg, bool iomgr_success) {
   grpc_subchannel *c = arg;
   gpr_mu_lock(&c->mu);
@@ -609,7 +579,8 @@ static void on_alarm(grpc_exec_ctx *exec_ctx, void *arg, bool iomgr_success) {
     iomgr_success = 0;
   }
   if (iomgr_success) {
-    update_reconnect_parameters(c);
+    c->next_attempt =
+        gpr_backoff_step(&c->backoff_state, gpr_now(GPR_CLOCK_MONOTONIC));
     continue_connect(exec_ctx, c);
     gpr_mu_unlock(&c->mu);
   } else {
@@ -641,17 +612,6 @@ static void subchannel_connected(grpc_exec_ctx *exec_ctx, void *arg,
   GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, c, "connecting");
 }
 
-static gpr_timespec compute_connect_deadline(grpc_subchannel *c) {
-  gpr_timespec current_deadline =
-      gpr_time_add(c->next_attempt, c->backoff_delta);
-  gpr_timespec min_deadline = gpr_time_add(
-      gpr_now(GPR_CLOCK_MONOTONIC),
-      gpr_time_from_seconds(GRPC_SUBCHANNEL_MIN_CONNECT_TIMEOUT_SECONDS,
-                            GPR_TIMESPAN));
-  return gpr_time_cmp(current_deadline, min_deadline) > 0 ? current_deadline
-                                                          : min_deadline;
-}
-
 /*
  * grpc_subchannel_call implementation
  */
diff --git a/src/core/support/backoff.c b/src/core/support/backoff.c
new file mode 100644
index 0000000000..7458219645
--- /dev/null
+++ b/src/core/support/backoff.c
@@ -0,0 +1,71 @@
+/*
+ *
+ * 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/support/backoff.h"
+
+#include <grpc/support/useful.h>
+
+void gpr_backoff_init(gpr_backoff *backoff, double multiplier, double jitter,
+                      int64_t min_timeout_millis, int64_t max_timeout_millis) {
+  backoff->multiplier = multiplier;
+  backoff->jitter = jitter;
+  backoff->min_timeout_millis = min_timeout_millis;
+  backoff->max_timeout_millis = max_timeout_millis;
+  backoff->rng_state = (uint32_t)gpr_now(GPR_CLOCK_REALTIME).tv_nsec;
+}
+
+gpr_timespec gpr_backoff_begin(gpr_backoff *backoff, gpr_timespec now) {
+  backoff->current_timeout_millis = backoff->min_timeout_millis;
+  return gpr_time_add(
+      now, gpr_time_from_millis(backoff->current_timeout_millis, GPR_TIMESPAN));
+}
+
+/* Generate a random number between 0 and 1. */
+static double generate_uniform_random_number(uint32_t *rng_state) {
+  *rng_state = (1103515245 * *rng_state + 12345) % ((uint32_t)1 << 31);
+  return *rng_state / (double)((uint32_t)1 << 31);
+}
+
+gpr_timespec gpr_backoff_step(gpr_backoff *backoff, gpr_timespec now) {
+  double new_timeout_millis =
+      backoff->multiplier * (double)backoff->current_timeout_millis;
+  double jitter_range = backoff->jitter * new_timeout_millis;
+  double jitter =
+      (2 * generate_uniform_random_number(&backoff->rng_state) - 1) *
+      jitter_range;
+  backoff->current_timeout_millis =
+      GPR_CLAMP((int64_t)(new_timeout_millis + jitter),
+                backoff->min_timeout_millis, backoff->max_timeout_millis);
+  return gpr_time_add(
+      now, gpr_time_from_millis(backoff->current_timeout_millis, GPR_TIMESPAN));
+}
diff --git a/src/core/support/backoff.h b/src/core/support/backoff.h
new file mode 100644
index 0000000000..3234aa214d
--- /dev/null
+++ b/src/core/support/backoff.h
@@ -0,0 +1,65 @@
+/*
+ *
+ * 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_SUPPORT_BACKOFF_H
+#define GRPC_INTERNAL_CORE_SUPPORT_BACKOFF_H
+
+#include <grpc/support/time.h>
+
+typedef struct {
+  /// const: multiplier between retry attempts
+  double multiplier;
+  /// const: amount to randomize backoffs
+  double jitter;
+  /// const: minimum time between retries in milliseconds
+  int64_t min_timeout_millis;
+  /// const: maximum time between retries in milliseconds
+  int64_t max_timeout_millis;
+
+  /// random number generator
+  uint32_t rng_state;
+
+  /// current retry timeout in milliseconds
+  int64_t current_timeout_millis;
+} gpr_backoff;
+
+/// Initialize backoff machinery - does not need to be destroyed
+void gpr_backoff_init(gpr_backoff *backoff, double multiplier, double jitter,
+                      int64_t min_timeout_millis, int64_t max_timeout_millis);
+
+/// Begin retry loop: returns a timespec for the NEXT retry
+gpr_timespec gpr_backoff_begin(gpr_backoff *backoff, gpr_timespec now);
+/// Step a retry loop: returns a timespec for the NEXT retry
+gpr_timespec gpr_backoff_step(gpr_backoff *backoff, gpr_timespec now);
+
+#endif  // GRPC_INTERNAL_CORE_SUPPORT_BACKOFF_H
diff --git a/src/python/grpcio/README.rst b/src/python/grpcio/README.rst
index 3dfae50b4b..3f4c6fad02 100644
--- a/src/python/grpcio/README.rst
+++ b/src/python/grpcio/README.rst
@@ -35,13 +35,14 @@ package named :code:`python-dev`).
 
 ::
 
-  $ export REPO_ROOT=grpc
+  $ export REPO_ROOT=grpc  # REPO_ROOT can be any directory of your choice
   $ git clone https://github.com/grpc/grpc.git $REPO_ROOT
   $ cd $REPO_ROOT
-  $ pip install .
 
-Note that :code:`$REPO_ROOT` can be assigned to whatever directory name floats
-your fancy.
+  # For the next two commands do `sudo pip install` if you get permission-denied errors
+  $ pip install -rrequirements.txt
+  $ GRPC_PYTHON_BUILD_WITH_CYTHON=1 pip install .
+
 
 Troubleshooting
 ~~~~~~~~~~~~~~~
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index ee375c42eb..b9e7d8c898 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -34,6 +34,7 @@ CORE_SOURCE_FILES = [
   'src/core/profiling/stap_timers.c',
   'src/core/support/alloc.c',
   'src/core/support/avl.c',
+  'src/core/support/backoff.c',
   'src/core/support/cmdline.c',
   'src/core/support/cpu_iphone.c',
   'src/core/support/cpu_linux.c',
diff --git a/test/core/support/backoff_test.c b/test/core/support/backoff_test.c
new file mode 100644
index 0000000000..870b60b2d5
--- /dev/null
+++ b/test/core/support/backoff_test.c
@@ -0,0 +1,107 @@
+/*
+ *
+ * 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/support/backoff.h"
+
+#include <grpc/support/log.h>
+
+#include "test/core/util/test_config.h"
+
+static void test_constant_backoff(void) {
+  gpr_backoff backoff;
+  gpr_backoff_init(&backoff, 1.0, 0.0, 1000, 1000);
+
+  gpr_timespec now = gpr_time_0(GPR_TIMESPAN);
+  gpr_timespec next = gpr_backoff_begin(&backoff, now);
+  GPR_ASSERT(gpr_time_to_millis(gpr_time_sub(next, now)) == 1000);
+  for (int i = 0; i < 10000; i++) {
+    next = gpr_backoff_step(&backoff, now);
+    GPR_ASSERT(gpr_time_to_millis(gpr_time_sub(next, now)) == 1000);
+    now = next;
+  }
+}
+
+static void test_no_jitter_backoff(void) {
+  gpr_backoff backoff;
+  gpr_backoff_init(&backoff, 2.0, 0.0, 1, 513);
+
+  gpr_timespec now = gpr_time_0(GPR_TIMESPAN);
+  gpr_timespec next = gpr_backoff_begin(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(1, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(3, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(7, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(15, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(31, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(63, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(127, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(255, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(511, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(1023, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(1536, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(2049, GPR_TIMESPAN), next) == 0);
+  now = next;
+  next = gpr_backoff_step(&backoff, now);
+  GPR_ASSERT(gpr_time_cmp(gpr_time_from_millis(2562, GPR_TIMESPAN), next) == 0);
+}
+
+int main(int argc, char **argv) {
+  grpc_test_init(argc, argv);
+  gpr_time_init();
+
+  test_constant_backoff();
+  test_no_jitter_backoff();
+
+  return 0;
+}
diff --git a/tools/doxygen/Doxyfile.core.internal b/tools/doxygen/Doxyfile.core.internal
index 66a3896292..4fcfba3983 100644
--- a/tools/doxygen/Doxyfile.core.internal
+++ b/tools/doxygen/Doxyfile.core.internal
@@ -1120,6 +1120,7 @@ include/grpc/impl/codegen/sync_posix.h \
 include/grpc/impl/codegen/sync_win32.h \
 include/grpc/impl/codegen/time.h \
 src/core/profiling/timers.h \
+src/core/support/backoff.h \
 src/core/support/block_annotate.h \
 src/core/support/env.h \
 src/core/support/load_file.h \
@@ -1134,6 +1135,7 @@ 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/backoff.c \
 src/core/support/cmdline.c \
 src/core/support/cpu_iphone.c \
 src/core/support/cpu_linux.c \
diff --git a/tools/run_tests/sources_and_headers.json b/tools/run_tests/sources_and_headers.json
index 392358088b..48b7b7c9a2 100644
--- a/tools/run_tests/sources_and_headers.json
+++ b/tools/run_tests/sources_and_headers.json
@@ -411,6 +411,20 @@
     ], 
     "headers": [], 
     "language": "c", 
+    "name": "gpr_backoff_test", 
+    "src": [
+      "test/core/support/backoff_test.c"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
+  {
+    "deps": [
+      "gpr", 
+      "gpr_test_util"
+    ], 
+    "headers": [], 
+    "language": "c", 
     "name": "gpr_cmdline_test", 
     "src": [
       "test/core/support/cmdline_test.c"
@@ -3780,6 +3794,7 @@
       "include/grpc/support/tls_pthread.h", 
       "include/grpc/support/useful.h", 
       "src/core/profiling/timers.h", 
+      "src/core/support/backoff.h", 
       "src/core/support/block_annotate.h", 
       "src/core/support/env.h", 
       "src/core/support/load_file.h", 
@@ -3841,6 +3856,8 @@
       "src/core/profiling/timers.h", 
       "src/core/support/alloc.c", 
       "src/core/support/avl.c", 
+      "src/core/support/backoff.c", 
+      "src/core/support/backoff.h", 
       "src/core/support/block_annotate.h", 
       "src/core/support/cmdline.c", 
       "src/core/support/cpu_iphone.c", 
diff --git a/tools/run_tests/tests.json b/tools/run_tests/tests.json
index 718e3dedcf..5daa58f20e 100644
--- a/tools/run_tests/tests.json
+++ b/tools/run_tests/tests.json
@@ -466,6 +466,27 @@
     "flaky": false, 
     "gtest": false, 
     "language": "c", 
+    "name": "gpr_backoff_test", 
+    "platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ]
+  }, 
+  {
+    "args": [], 
+    "ci_platforms": [
+      "linux", 
+      "mac", 
+      "posix", 
+      "windows"
+    ], 
+    "cpu_cost": 1.0, 
+    "exclude_configs": [], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c", 
     "name": "gpr_cmdline_test", 
     "platforms": [
       "linux", 
@@ -2295,7 +2316,7 @@
       "mac", 
       "posix"
     ], 
-    "cpu_cost": 10, 
+    "cpu_cost": 0.5, 
     "exclude_configs": [], 
     "flaky": false, 
     "gtest": false, 
diff --git a/vsprojects/buildtests_c.sln b/vsprojects/buildtests_c.sln
index 3a31672201..8c64423b51 100644
--- a/vsprojects/buildtests_c.sln
+++ b/vsprojects/buildtests_c.sln
@@ -334,6 +334,15 @@ Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "gpr_avl_test", "vcxproj\tes
 		{B23D3D1A-9438-4EDA-BEB6-9A0A03D17792} = {B23D3D1A-9438-4EDA-BEB6-9A0A03D17792}
 	EndProjectSection
 EndProject
+Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "gpr_backoff_test", "vcxproj\test\gpr_backoff_test\gpr_backoff_test.vcxproj", "{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}"
+	ProjectSection(myProperties) = preProject
+        	lib = "False"
+	EndProjectSection
+	ProjectSection(ProjectDependencies) = postProject
+		{EAB0A629-17A9-44DB-B5FF-E91A721FE037} = {EAB0A629-17A9-44DB-B5FF-E91A721FE037}
+		{B23D3D1A-9438-4EDA-BEB6-9A0A03D17792} = {B23D3D1A-9438-4EDA-BEB6-9A0A03D17792}
+	EndProjectSection
+EndProject
 Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "gpr_cmdline_test", "vcxproj\test\gpr_cmdline_test\gpr_cmdline_test.vcxproj", "{10668A5D-65CD-F530-22D0-747B395B4C26}"
 	ProjectSection(myProperties) = preProject
         	lib = "False"
@@ -1892,6 +1901,22 @@ Global
 		{144D8CFF-2737-A18A-DCFD-01603533D63F}.Release-DLL|Win32.Build.0 = Release|Win32
 		{144D8CFF-2737-A18A-DCFD-01603533D63F}.Release-DLL|x64.ActiveCfg = Release|x64
 		{144D8CFF-2737-A18A-DCFD-01603533D63F}.Release-DLL|x64.Build.0 = Release|x64
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Debug|Win32.ActiveCfg = Debug|Win32
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Debug|x64.ActiveCfg = Debug|x64
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Release|Win32.ActiveCfg = Release|Win32
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Release|x64.ActiveCfg = Release|x64
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Debug|Win32.Build.0 = Debug|Win32
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Debug|x64.Build.0 = Debug|x64
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Release|Win32.Build.0 = Release|Win32
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Release|x64.Build.0 = Release|x64
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Debug-DLL|Win32.ActiveCfg = Debug|Win32
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Debug-DLL|Win32.Build.0 = Debug|Win32
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Debug-DLL|x64.ActiveCfg = Debug|x64
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Debug-DLL|x64.Build.0 = Debug|x64
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Release-DLL|Win32.ActiveCfg = Release|Win32
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Release-DLL|Win32.Build.0 = Release|Win32
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Release-DLL|x64.ActiveCfg = Release|x64
+		{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}.Release-DLL|x64.Build.0 = Release|x64
 		{10668A5D-65CD-F530-22D0-747B395B4C26}.Debug|Win32.ActiveCfg = Debug|Win32
 		{10668A5D-65CD-F530-22D0-747B395B4C26}.Debug|x64.ActiveCfg = Debug|x64
 		{10668A5D-65CD-F530-22D0-747B395B4C26}.Release|Win32.ActiveCfg = Release|Win32
diff --git a/vsprojects/vcxproj/gpr/gpr.vcxproj b/vsprojects/vcxproj/gpr/gpr.vcxproj
index dae8e623d8..9281fa3995 100644
--- a/vsprojects/vcxproj/gpr/gpr.vcxproj
+++ b/vsprojects/vcxproj/gpr/gpr.vcxproj
@@ -192,6 +192,7 @@
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="$(SolutionDir)\..\src\core\profiling\timers.h" />
+    <ClInclude Include="$(SolutionDir)\..\src\core\support\backoff.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\support\block_annotate.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\support\env.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\support\load_file.h" />
@@ -212,6 +213,8 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\support\avl.c">
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\support\backoff.c">
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\support\cmdline.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\support\cpu_iphone.c">
diff --git a/vsprojects/vcxproj/gpr/gpr.vcxproj.filters b/vsprojects/vcxproj/gpr/gpr.vcxproj.filters
index 055b29f648..b85060f385 100644
--- a/vsprojects/vcxproj/gpr/gpr.vcxproj.filters
+++ b/vsprojects/vcxproj/gpr/gpr.vcxproj.filters
@@ -13,6 +13,9 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\support\avl.c">
       <Filter>src\core\support</Filter>
     </ClCompile>
+    <ClCompile Include="$(SolutionDir)\..\src\core\support\backoff.c">
+      <Filter>src\core\support</Filter>
+    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\support\cmdline.c">
       <Filter>src\core\support</Filter>
     </ClCompile>
@@ -263,6 +266,9 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\profiling\timers.h">
       <Filter>src\core\profiling</Filter>
     </ClInclude>
+    <ClInclude Include="$(SolutionDir)\..\src\core\support\backoff.h">
+      <Filter>src\core\support</Filter>
+    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\support\block_annotate.h">
       <Filter>src\core\support</Filter>
     </ClInclude>
diff --git a/vsprojects/vcxproj/test/gpr_backoff_test/gpr_backoff_test.vcxproj b/vsprojects/vcxproj/test/gpr_backoff_test/gpr_backoff_test.vcxproj
new file mode 100644
index 0000000000..6aa292ef4f
--- /dev/null
+++ b/vsprojects/vcxproj/test/gpr_backoff_test/gpr_backoff_test.vcxproj
@@ -0,0 +1,193 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="12.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(SolutionDir)\..\vsprojects\packages\grpc.dependencies.openssl.1.0.204.1\build\native\grpc.dependencies.openssl.props" Condition="Exists('$(SolutionDir)\..\vsprojects\packages\grpc.dependencies.openssl.1.0.204.1\build\native\1.0.204.1.props')" />
+  <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|Win32">
+      <Configuration>Debug</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|x64">
+      <Configuration>Debug</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|Win32">
+      <Configuration>Release</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|x64">
+      <Configuration>Release</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+  </ItemGroup>
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>{889F570D-E046-BD52-9E4C-B4CD13DFE2DB}</ProjectGuid>
+    <IgnoreWarnIntDirInTempDetected>true</IgnoreWarnIntDirInTempDetected>
+    <IntDir>$(SolutionDir)IntDir\$(MSBuildProjectName)\</IntDir>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <PropertyGroup Condition="'$(VisualStudioVersion)' == '10.0'" Label="Configuration">
+    <PlatformToolset>v100</PlatformToolset>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(VisualStudioVersion)' == '11.0'" Label="Configuration">
+    <PlatformToolset>v110</PlatformToolset>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(VisualStudioVersion)' == '12.0'" Label="Configuration">
+    <PlatformToolset>v120</PlatformToolset>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(VisualStudioVersion)' == '14.0'" Label="Configuration">
+    <PlatformToolset>v140</PlatformToolset>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)'=='Debug'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <UseDebugLibraries>true</UseDebugLibraries>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(Configuration)'=='Release'" Label="Configuration">
+    <ConfigurationType>Application</ConfigurationType>
+    <UseDebugLibraries>false</UseDebugLibraries>
+    <WholeProgramOptimization>true</WholeProgramOptimization>
+    <CharacterSet>Unicode</CharacterSet>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="$(SolutionDir)\..\vsprojects\global.props" />
+    <Import Project="$(SolutionDir)\..\vsprojects\openssl.props" />
+    <Import Project="$(SolutionDir)\..\vsprojects\winsock.props" />
+    <Import Project="$(SolutionDir)\..\vsprojects\zlib.props" />
+  </ImportGroup>
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diff --git a/vsprojects/vcxproj/test/gpr_backoff_test/gpr_backoff_test.vcxproj.filters b/vsprojects/vcxproj/test/gpr_backoff_test/gpr_backoff_test.vcxproj.filters
new file mode 100644
index 0000000000..eb3c1bbd8c
--- /dev/null
+++ b/vsprojects/vcxproj/test/gpr_backoff_test/gpr_backoff_test.vcxproj.filters
@@ -0,0 +1,21 @@
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+<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
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