Merge pull request #4859 from ctiller/sceq

Subchannel Sharing  [The interop tests failures and Basic test failures are unrelated to this change. Merging]

BUILD

@@ -194,6 +194,7 @@ cc_library(
     "src/core/client_config/resolvers/sockaddr_resolver.h",
     "src/core/client_config/subchannel.h",
     "src/core/client_config/subchannel_factory.h",
+    "src/core/client_config/subchannel_index.h",
     "src/core/client_config/uri_parser.h",
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",
@@ -332,6 +333,7 @@ cc_library(
     "src/core/client_config/resolvers/sockaddr_resolver.c",
     "src/core/client_config/subchannel.c",
     "src/core/client_config/subchannel_factory.c",
+    "src/core/client_config/subchannel_index.c",
     "src/core/client_config/uri_parser.c",
     "src/core/compression/algorithm.c",
     "src/core/compression/message_compress.c",
@@ -498,6 +500,7 @@ cc_library(
     "src/core/client_config/resolvers/sockaddr_resolver.h",
     "src/core/client_config/subchannel.h",
     "src/core/client_config/subchannel_factory.h",
+    "src/core/client_config/subchannel_index.h",
     "src/core/client_config/uri_parser.h",
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",
@@ -616,6 +619,7 @@ cc_library(
     "src/core/client_config/resolvers/sockaddr_resolver.c",
     "src/core/client_config/subchannel.c",
     "src/core/client_config/subchannel_factory.c",
+    "src/core/client_config/subchannel_index.c",
     "src/core/client_config/uri_parser.c",
     "src/core/compression/algorithm.c",
     "src/core/compression/message_compress.c",
@@ -1293,6 +1297,7 @@ objc_library(
     "src/core/client_config/resolvers/sockaddr_resolver.c",
     "src/core/client_config/subchannel.c",
     "src/core/client_config/subchannel_factory.c",
+    "src/core/client_config/subchannel_index.c",
     "src/core/client_config/uri_parser.c",
     "src/core/compression/algorithm.c",
     "src/core/compression/message_compress.c",
@@ -1454,6 +1459,7 @@ objc_library(
     "src/core/client_config/resolvers/sockaddr_resolver.h",
     "src/core/client_config/subchannel.h",
     "src/core/client_config/subchannel_factory.h",
+    "src/core/client_config/subchannel_index.h",
     "src/core/client_config/uri_parser.h",
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",

Makefile

@@ -2366,6 +2366,7 @@ LIBGRPC_SRC = \
     src/core/client_config/resolvers/sockaddr_resolver.c \
     src/core/client_config/subchannel.c \
     src/core/client_config/subchannel_factory.c \
+    src/core/client_config/subchannel_index.c \
     src/core/client_config/uri_parser.c \
     src/core/compression/algorithm.c \
     src/core/compression/message_compress.c \
@@ -2651,6 +2652,7 @@ LIBGRPC_UNSECURE_SRC = \
     src/core/client_config/resolvers/sockaddr_resolver.c \
     src/core/client_config/subchannel.c \
     src/core/client_config/subchannel_factory.c \
+    src/core/client_config/subchannel_index.c \
     src/core/client_config/uri_parser.c \
     src/core/compression/algorithm.c \
     src/core/compression/message_compress.c \

binding.gyp

@@ -605,6 +605,7 @@
         'src/core/client_config/resolvers/sockaddr_resolver.c',
         'src/core/client_config/subchannel.c',
         'src/core/client_config/subchannel_factory.c',
+        'src/core/client_config/subchannel_index.c',
         'src/core/client_config/uri_parser.c',
         'src/core/compression/algorithm.c',
         'src/core/compression/message_compress.c',

build.yaml

@@ -270,6 +270,7 @@ filegroups:
   - src/core/client_config/resolvers/sockaddr_resolver.h
   - src/core/client_config/subchannel.h
   - src/core/client_config/subchannel_factory.h
+  - src/core/client_config/subchannel_index.h
   - src/core/client_config/uri_parser.h
   - src/core/compression/algorithm_metadata.h
   - src/core/compression/message_compress.h
@@ -385,6 +386,7 @@ filegroups:
   - src/core/client_config/resolvers/sockaddr_resolver.c
   - src/core/client_config/subchannel.c
   - src/core/client_config/subchannel_factory.c
+  - src/core/client_config/subchannel_index.c
   - src/core/client_config/uri_parser.c
   - src/core/compression/algorithm.c
   - src/core/compression/message_compress.c
@@ -2627,8 +2629,8 @@ configs:
     LDXX: clang++
     compile_the_world: true
     test_environ:
-      ASAN_OPTIONS: suppressions=tools/asan_suppressions.txt:detect_leaks=1:color=always
-      LSAN_OPTIONS: suppressions=tools/asan_suppressions.txt:report_objects=1
+      ASAN_OPTIONS: detect_leaks=1:color=always
+      LSAN_OPTIONS: suppressions=tools/lsan_suppressions.txt:report_objects=1
     timeout_multiplier: 1.5
   asan-noleaks:
     CC: clang

gRPC.podspec

@@ -198,6 +198,7 @@ Pod::Spec.new do |s|
                       'src/core/client_config/resolvers/sockaddr_resolver.h',
                       'src/core/client_config/subchannel.h',
                       'src/core/client_config/subchannel_factory.h',
+                      'src/core/client_config/subchannel_index.h',
                       'src/core/client_config/uri_parser.h',
                       'src/core/compression/algorithm_metadata.h',
                       'src/core/compression/message_compress.h',
@@ -349,6 +350,7 @@ Pod::Spec.new do |s|
                       'src/core/client_config/resolvers/sockaddr_resolver.c',
                       'src/core/client_config/subchannel.c',
                       'src/core/client_config/subchannel_factory.c',
+                      'src/core/client_config/subchannel_index.c',
                       'src/core/client_config/uri_parser.c',
                       'src/core/compression/algorithm.c',
                       'src/core/compression/message_compress.c',
@@ -506,6 +508,7 @@ Pod::Spec.new do |s|
                               'src/core/client_config/resolvers/sockaddr_resolver.h',
                               'src/core/client_config/subchannel.h',
                               'src/core/client_config/subchannel_factory.h',
+                              'src/core/client_config/subchannel_index.h',
                               'src/core/client_config/uri_parser.h',
                               'src/core/compression/algorithm_metadata.h',
                               'src/core/compression/message_compress.h',

grpc.gemspec

@@ -194,6 +194,7 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/client_config/resolvers/sockaddr_resolver.h )
   s.files += %w( src/core/client_config/subchannel.h )
   s.files += %w( src/core/client_config/subchannel_factory.h )
+  s.files += %w( src/core/client_config/subchannel_index.h )
   s.files += %w( src/core/client_config/uri_parser.h )
   s.files += %w( src/core/compression/algorithm_metadata.h )
   s.files += %w( src/core/compression/message_compress.h )
@@ -332,6 +333,7 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/client_config/resolvers/sockaddr_resolver.c )
   s.files += %w( src/core/client_config/subchannel.c )
   s.files += %w( src/core/client_config/subchannel_factory.c )
+  s.files += %w( src/core/client_config/subchannel_index.c )
   s.files += %w( src/core/client_config/uri_parser.c )
   s.files += %w( src/core/compression/algorithm.c )
   s.files += %w( src/core/compression/message_compress.c )

include/grpc/impl/codegen/grpc_types.h

@@ -68,6 +68,12 @@ typedef enum {
   GRPC_ARG_POINTER
 } grpc_arg_type;
 
+typedef struct grpc_arg_pointer_vtable {
+  void *(*copy)(void *p);
+  void (*destroy)(void *p);
+  int (*cmp)(void *p, void *q);
+} grpc_arg_pointer_vtable;
+
 /** A single argument... each argument has a key and a value
 
     A note on naming keys:
@@ -88,8 +94,7 @@ typedef struct {
     int integer;
     struct {
       void *p;
-      void *(*copy)(void *p);
-      void (*destroy)(void *p);
+      const grpc_arg_pointer_vtable *vtable;
     } pointer;
   } value;
 } grpc_arg;

include/grpc/support/avl.h

@@ -81,11 +81,12 @@ GPRAPI void gpr_avl_unref(gpr_avl avl);
     if key exists in avl, the new tree's key entry updated
     (i.e. a duplicate is not created) */
 GPRAPI gpr_avl gpr_avl_add(gpr_avl avl, void *key, void *value);
-/** return a new tree with key deleted */
+/** return a new tree with key deleted
+    implicitly unrefs avl to allow easy chaining. */
 GPRAPI gpr_avl gpr_avl_remove(gpr_avl avl, void *key);
 /** lookup key, and return the associated value.
     does not mutate avl.
     returns NULL if key is not found. */
 GPRAPI void *gpr_avl_get(gpr_avl avl, void *key);
 
-#endif
+#endif /* GRPC_SUPPORT_AVL_H */

include/grpc/support/useful.h

 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -72,4 +72,6 @@
     0x0f0f0f0f) %                                \
    255)
 
+#define GPR_ICMP(a, b) ((a) < (b) ? -1 : ((a) > (b) ? 1 : 0))
+
 #endif /* GRPC_SUPPORT_USEFUL_H */

package.json

@@ -139,6 +139,7 @@
     "src/core/client_config/resolvers/sockaddr_resolver.h",
     "src/core/client_config/subchannel.h",
     "src/core/client_config/subchannel_factory.h",
+    "src/core/client_config/subchannel_index.h",
     "src/core/client_config/uri_parser.h",
     "src/core/compression/algorithm_metadata.h",
     "src/core/compression/message_compress.h",
@@ -277,6 +278,7 @@
     "src/core/client_config/resolvers/sockaddr_resolver.c",
     "src/core/client_config/subchannel.c",
     "src/core/client_config/subchannel_factory.c",
+    "src/core/client_config/subchannel_index.c",
     "src/core/client_config/uri_parser.c",
     "src/core/compression/algorithm.c",
     "src/core/compression/message_compress.c",

src/core/channel/channel_args.c

@@ -37,6 +37,7 @@
 
 #include <grpc/census.h>
 #include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/useful.h>
 
@@ -55,9 +56,8 @@ static grpc_arg copy_arg(const grpc_arg *src) {
       break;
     case GRPC_ARG_POINTER:
       dst.value.pointer = src->value.pointer;
-      dst.value.pointer.p = src->value.pointer.copy
-                                ? src->value.pointer.copy(src->value.pointer.p)
-                                : src->value.pointer.p;
+      dst.value.pointer.p =
+          src->value.pointer.vtable->copy(src->value.pointer.p);
       break;
   }
   return dst;
@@ -94,6 +94,58 @@ grpc_channel_args *grpc_channel_args_merge(const grpc_channel_args *a,
   return grpc_channel_args_copy_and_add(a, b->args, b->num_args);
 }
 
+static int cmp_arg(const grpc_arg *a, const grpc_arg *b) {
+  int c = GPR_ICMP(a->type, b->type);
+  if (c != 0) return c;
+  c = strcmp(a->key, b->key);
+  if (c != 0) return c;
+  switch (a->type) {
+    case GRPC_ARG_STRING:
+      return strcmp(a->value.string, b->value.string);
+    case GRPC_ARG_INTEGER:
+      return GPR_ICMP(a->value.integer, b->value.integer);
+    case GRPC_ARG_POINTER:
+      c = GPR_ICMP(a->value.pointer.p, b->value.pointer.p);
+      if (c != 0) {
+        c = GPR_ICMP(a->value.pointer.vtable, b->value.pointer.vtable);
+        if (c == 0) {
+          c = a->value.pointer.vtable->cmp(a->value.pointer.p,
+                                           b->value.pointer.p);
+        }
+      }
+      return c;
+  }
+  GPR_UNREACHABLE_CODE(return 0);
+}
+
+/* stabilizing comparison function: since channel_args ordering matters for
+ * keys with the same name, we need to preserve that ordering */
+static int cmp_key_stable(const void *ap, const void *bp) {
+  const grpc_arg *const *a = ap;
+  const grpc_arg *const *b = bp;
+  int c = strcmp((*a)->key, (*b)->key);
+  if (c == 0) c = GPR_ICMP(*a, *b);
+  return c;
+}
+
+grpc_channel_args *grpc_channel_args_normalize(const grpc_channel_args *a) {
+  grpc_arg **args = gpr_malloc(sizeof(grpc_arg *) * a->num_args);
+  for (size_t i = 0; i < a->num_args; i++) {
+    args[i] = &a->args[i];
+  }
+  qsort(args, a->num_args, sizeof(grpc_arg *), cmp_key_stable);
+
+  grpc_channel_args *b = gpr_malloc(sizeof(grpc_channel_args));
+  b->num_args = a->num_args;
+  b->args = gpr_malloc(sizeof(grpc_arg) * b->num_args);
+  for (size_t i = 0; i < a->num_args; i++) {
+    b->args[i] = copy_arg(args[i]);
+  }
+
+  gpr_free(args);
+  return b;
+}
+
 void grpc_channel_args_destroy(grpc_channel_args *a) {
   size_t i;
   for (i = 0; i < a->num_args; i++) {
@@ -104,9 +156,7 @@ void grpc_channel_args_destroy(grpc_channel_args *a) {
       case GRPC_ARG_INTEGER:
         break;
       case GRPC_ARG_POINTER:
-        if (a->args[i].value.pointer.destroy) {
-          a->args[i].value.pointer.destroy(a->args[i].value.pointer.p);
-        }
+        a->args[i].value.pointer.vtable->destroy(a->args[i].value.pointer.p);
         break;
     }
     gpr_free(a->args[i].key);
@@ -208,3 +258,14 @@ int grpc_channel_args_compression_algorithm_get_states(
     return (1u << GRPC_COMPRESS_ALGORITHMS_COUNT) - 1; /* All algs. enabled */
   }
 }
+
+int grpc_channel_args_compare(const grpc_channel_args *a,
+                              const grpc_channel_args *b) {
+  int c = GPR_ICMP(a->num_args, b->num_args);
+  if (c != 0) return c;
+  for (size_t i = 0; i < a->num_args; i++) {
+    c = cmp_arg(&a->args[i], &b->args[i]);
+    if (c != 0) return c;
+  }
+  return 0;
+}

src/core/channel/channel_args.h

 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -40,6 +40,9 @@
 /* Copy some arguments */
 grpc_channel_args *grpc_channel_args_copy(const grpc_channel_args *src);
 
+/* Copy some arguments, stably sorting keys */
+grpc_channel_args *grpc_channel_args_normalize(const grpc_channel_args *a);
+
 /** Copy some arguments and add the to_add parameter in the end.
    If to_add is NULL, it is equivalent to call grpc_channel_args_copy. */
 grpc_channel_args *grpc_channel_args_copy_and_add(const grpc_channel_args *src,
@@ -85,4 +88,7 @@ grpc_channel_args *grpc_channel_args_compression_algorithm_set_state(
 int grpc_channel_args_compression_algorithm_get_states(
     const grpc_channel_args *a);
 
+int grpc_channel_args_compare(const grpc_channel_args *a,
+                              const grpc_channel_args *b);
+
 #endif /* GRPC_INTERNAL_CORE_CHANNEL_CHANNEL_ARGS_H */

src/core/client_config/connector.c

 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -33,8 +33,9 @@
 
 #include "src/core/client_config/connector.h"
 
-void grpc_connector_ref(grpc_connector* connector) {
+grpc_connector* grpc_connector_ref(grpc_connector* connector) {
   connector->vtable->ref(connector);
+  return connector;
 }
 
 void grpc_connector_unref(grpc_exec_ctx* exec_ctx, grpc_connector* connector) {

src/core/client_config/connector.h

 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -81,7 +81,7 @@ struct grpc_connector_vtable {
                   grpc_connect_out_args *out_args, grpc_closure *notify);
 };
 
-void grpc_connector_ref(grpc_connector *connector);
+grpc_connector *grpc_connector_ref(grpc_connector *connector);
 void grpc_connector_unref(grpc_exec_ctx *exec_ctx, grpc_connector *connector);
 /** Connect using the connector: max one outstanding call at a time */
 void grpc_connector_connect(grpc_exec_ctx *exec_ctx, grpc_connector *connector,

src/core/client_config/subchannel.c

@@ -36,16 +36,17 @@
 #include <string.h>
 
 #include <grpc/support/alloc.h>
+#include <grpc/support/avl.h>
 
 #include "src/core/channel/channel_args.h"
 #include "src/core/channel/client_channel.h"
 #include "src/core/channel/connected_channel.h"
 #include "src/core/client_config/initial_connect_string.h"
+#include "src/core/client_config/subchannel_index.h"
 #include "src/core/iomgr/timer.h"
 #include "src/core/profiling/timers.h"
 #include "src/core/surface/channel.h"
 #include "src/core/transport/connectivity_state.h"
-#include "src/core/transport/connectivity_state.h"
 
 #define INTERNAL_REF_BITS 16
 #define STRONG_REF_MASK (~(gpr_atm)((1 << INTERNAL_REF_BITS) - 1))
@@ -94,6 +95,8 @@ struct grpc_subchannel {
   struct sockaddr *addr;
   size_t addr_len;
 
+  grpc_subchannel_key *key;
+
   /** initial string to send to peer */
   gpr_slice initial_connect_string;
 
@@ -207,6 +210,7 @@ static void subchannel_destroy(grpc_exec_ctx *exec_ctx, void *arg,
   grpc_connectivity_state_destroy(exec_ctx, &c->state_tracker);
   grpc_connector_unref(exec_ctx, c->connector);
   grpc_pollset_set_destroy(&c->pollset_set);
+  grpc_subchannel_key_destroy(exec_ctx, c->key);
   gpr_free(c);
 }
 
@@ -222,22 +226,42 @@ static gpr_atm ref_mutate(grpc_subchannel *c, gpr_atm delta,
   return old_val;
 }
 
-void grpc_subchannel_ref(grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+grpc_subchannel *grpc_subchannel_ref(grpc_subchannel *c
+                                         GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
   gpr_atm old_refs;
   old_refs = ref_mutate(c, (1 << INTERNAL_REF_BITS),
                         0 REF_MUTATE_PURPOSE("STRONG_REF"));
   GPR_ASSERT((old_refs & STRONG_REF_MASK) != 0);
+  return c;
 }
 
-void grpc_subchannel_weak_ref(grpc_subchannel *c
+grpc_subchannel *grpc_subchannel_weak_ref(grpc_subchannel *c
                                               GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
   gpr_atm old_refs;
   old_refs = ref_mutate(c, 1, 0 REF_MUTATE_PURPOSE("WEAK_REF"));
   GPR_ASSERT(old_refs != 0);
+  return c;
+}
+
+grpc_subchannel *grpc_subchannel_ref_from_weak_ref(
+    grpc_subchannel *c GRPC_SUBCHANNEL_REF_EXTRA_ARGS) {
+  if (!c) return NULL;
+  for (;;) {
+    gpr_atm old_refs = gpr_atm_acq_load(&c->ref_pair);
+    if (old_refs >= (1 << INTERNAL_REF_BITS)) {
+      gpr_atm new_refs = old_refs + (1 << INTERNAL_REF_BITS);
+      if (gpr_atm_rel_cas(&c->ref_pair, old_refs, new_refs)) {
+        return c;
+      }
+    } else {
+      return NULL;
+    }
+  }
 }
 
 static void disconnect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {
   grpc_connected_subchannel *con;
+  grpc_subchannel_index_unregister(exec_ctx, c->key, c);
   gpr_mu_lock(&c->mu);
   GPR_ASSERT(!c->disconnected);
   c->disconnected = 1;
@@ -276,10 +300,19 @@ static uint32_t random_seed() {
   return (uint32_t)(gpr_time_to_millis(gpr_now(GPR_CLOCK_MONOTONIC)));
 }
 
-grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
+grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
+                                        grpc_connector *connector,
                                         grpc_subchannel_args *args) {
-  grpc_subchannel *c = gpr_malloc(sizeof(*c));
+  grpc_subchannel_key *key = grpc_subchannel_key_create(connector, args);
+  grpc_subchannel *c = grpc_subchannel_index_find(exec_ctx, key);
+  if (c) {
+    grpc_subchannel_key_destroy(exec_ctx, key);
+    return c;
+  }
+
+  c = gpr_malloc(sizeof(*c));
   memset(c, 0, sizeof(*c));
+  c->key = key;
   gpr_atm_no_barrier_store(&c->ref_pair, 1 << INTERNAL_REF_BITS);
   c->connector = connector;
   grpc_connector_ref(c->connector);
@@ -305,7 +338,8 @@ grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
   grpc_connectivity_state_init(&c->state_tracker, GRPC_CHANNEL_IDLE,
                                "subchannel");
   gpr_mu_init(&c->mu);
-  return c;
+
+  return grpc_subchannel_index_register(exec_ctx, key, c);
 }
 
 static void continue_connect(grpc_exec_ctx *exec_ctx, grpc_subchannel *c) {

src/core/client_config/subchannel.h

 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -48,6 +48,8 @@ typedef struct grpc_subchannel_args grpc_subchannel_args;
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
 #define GRPC_SUBCHANNEL_REF(p, r) \
   grpc_subchannel_ref((p), __FILE__, __LINE__, (r))
+#define GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(p, r) \
+  grpc_subchannel_ref_from_weak_ref((p), __FILE__, __LINE__, (r))
 #define GRPC_SUBCHANNEL_UNREF(cl, p, r) \
   grpc_subchannel_unref((cl), (p), __FILE__, __LINE__, (r))
 #define GRPC_SUBCHANNEL_WEAK_REF(p, r) \
@@ -66,6 +68,8 @@ typedef struct grpc_subchannel_args grpc_subchannel_args;
   , const char *file, int line, const char *reason
 #else
 #define GRPC_SUBCHANNEL_REF(p, r) grpc_subchannel_ref((p))
+#define GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(p, r) \
+  grpc_subchannel_ref_from_weak_ref((p))
 #define GRPC_SUBCHANNEL_UNREF(cl, p, r) grpc_subchannel_unref((cl), (p))
 #define GRPC_SUBCHANNEL_WEAK_REF(p, r) grpc_subchannel_weak_ref((p))
 #define GRPC_SUBCHANNEL_WEAK_UNREF(cl, p, r) \
@@ -79,12 +83,14 @@ typedef struct grpc_subchannel_args grpc_subchannel_args;
 #define GRPC_SUBCHANNEL_REF_EXTRA_ARGS
 #endif
 
-void grpc_subchannel_ref(grpc_subchannel *channel
+grpc_subchannel *grpc_subchannel_ref(grpc_subchannel *channel
                                          GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
+grpc_subchannel *grpc_subchannel_ref_from_weak_ref(
+    grpc_subchannel *channel GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
 void grpc_subchannel_unref(grpc_exec_ctx *exec_ctx,
                            grpc_subchannel *channel
                                GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
-void grpc_subchannel_weak_ref(grpc_subchannel *channel
+grpc_subchannel *grpc_subchannel_weak_ref(grpc_subchannel *channel
                                               GRPC_SUBCHANNEL_REF_EXTRA_ARGS);
 void grpc_subchannel_weak_unref(grpc_exec_ctx *exec_ctx,
                                 grpc_subchannel *channel
@@ -146,6 +152,8 @@ grpc_call_stack *grpc_subchannel_call_get_call_stack(
     grpc_subchannel_call *subchannel_call);
 
 struct grpc_subchannel_args {
+  /* When updating this struct, also update subchannel_index.c */
+
   /** Channel filters for this channel - wrapped factories will likely
       want to mutate this */
   const grpc_channel_filter **filters;
@@ -159,7 +167,8 @@ struct grpc_subchannel_args {
 };
 
 /** create a subchannel given a connector */
-grpc_subchannel *grpc_subchannel_create(grpc_connector *connector,
+grpc_subchannel *grpc_subchannel_create(grpc_exec_ctx *exec_ctx,
+                                        grpc_connector *connector,
                                         grpc_subchannel_args *args);
 
 #endif /* GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_H */

src/core/client_config/subchannel_index.c

+//
+//
+// Copyright 2016, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//
+
+#include "src/core/client_config/subchannel_index.h"
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/avl.h>
+#include <grpc/support/tls.h>
+
+#include "src/core/channel/channel_args.h"
+
+// a map of subchannel_key --> subchannel, used for detecting connections
+// to the same destination in order to share them
+static gpr_avl g_subchannel_index;
+
+static gpr_mu g_mu;
+
+struct grpc_subchannel_key {
+  grpc_connector *connector;
+  grpc_subchannel_args args;
+};
+
+GPR_TLS_DECL(subchannel_index_exec_ctx);
+
+static void enter_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_ASSERT(gpr_tls_get(&subchannel_index_exec_ctx) == 0);
+  gpr_tls_set(&subchannel_index_exec_ctx, (intptr_t)exec_ctx);
+}
+
+static void leave_ctx(grpc_exec_ctx *exec_ctx) {
+  GPR_ASSERT(gpr_tls_get(&subchannel_index_exec_ctx) == (intptr_t)exec_ctx);
+  gpr_tls_set(&subchannel_index_exec_ctx, 0);
+}
+
+static grpc_exec_ctx *current_ctx() {
+  grpc_exec_ctx *c = (grpc_exec_ctx *)gpr_tls_get(&subchannel_index_exec_ctx);
+  GPR_ASSERT(c != NULL);
+  return c;
+}
+
+static grpc_subchannel_key *create_key(
+    grpc_connector *connector, grpc_subchannel_args *args,
+    grpc_channel_args *(*copy_channel_args)(const grpc_channel_args *args)) {
+  grpc_subchannel_key *k = gpr_malloc(sizeof(*k));
+  k->connector = grpc_connector_ref(connector);
+  k->args.filter_count = args->filter_count;
+  k->args.filters = gpr_malloc(sizeof(*k->args.filters) * k->args.filter_count);
+  memcpy((grpc_channel_filter *)k->args.filters, args->filters,
+         sizeof(*k->args.filters) * k->args.filter_count);
+  k->args.addr_len = args->addr_len;
+  k->args.addr = gpr_malloc(args->addr_len);
+  memcpy(k->args.addr, args->addr, k->args.addr_len);
+  k->args.args = copy_channel_args(args->args);
+  return k;
+}
+
+grpc_subchannel_key *grpc_subchannel_key_create(grpc_connector *connector,
+                                                grpc_subchannel_args *args) {
+  return create_key(connector, args, grpc_channel_args_normalize);
+}
+
+static grpc_subchannel_key *subchannel_key_copy(grpc_subchannel_key *k) {
+  return create_key(k->connector, &k->args, grpc_channel_args_copy);
+}
+
+static int subchannel_key_compare(grpc_subchannel_key *a,
+                                  grpc_subchannel_key *b) {
+  int c = GPR_ICMP(a->connector, b->connector);
+  if (c != 0) return c;
+  c = GPR_ICMP(a->args.addr_len, b->args.addr_len);
+  if (c != 0) return c;
+  c = GPR_ICMP(a->args.filter_count, b->args.filter_count);
+  if (c != 0) return c;
+  c = memcmp(a->args.addr, b->args.addr, a->args.addr_len);
+  if (c != 0) return c;
+  c = memcmp(a->args.filters, b->args.filters,
+             a->args.filter_count * sizeof(*a->args.filters));
+  return grpc_channel_args_compare(a->args.args, b->args.args);
+}
+
+void grpc_subchannel_key_destroy(grpc_exec_ctx *exec_ctx,
+                                 grpc_subchannel_key *k) {
+  grpc_connector_unref(exec_ctx, k->connector);
+  gpr_free(k->args.addr);
+  gpr_free((grpc_channel_args *)k->args.filters);
+  grpc_channel_args_destroy((grpc_channel_args *)k->args.args);
+  gpr_free(k);
+}
+
+static void sck_avl_destroy(void *p) {
+  grpc_subchannel_key_destroy(current_ctx(), p);
+}
+
+static void *sck_avl_copy(void *p) { return subchannel_key_copy(p); }
+
+static long sck_avl_compare(void *a, void *b) {
+  return subchannel_key_compare(a, b);
+}
+
+static void scv_avl_destroy(void *p) {
+  GRPC_SUBCHANNEL_WEAK_UNREF(current_ctx(), p, "subchannel_index");
+}
+
+static void *scv_avl_copy(void *p) {
+  GRPC_SUBCHANNEL_WEAK_REF(p, "subchannel_index");
+  return p;
+}
+
+static const gpr_avl_vtable subchannel_avl_vtable = {
+    .destroy_key = sck_avl_destroy,
+    .copy_key = sck_avl_copy,
+    .compare_keys = sck_avl_compare,
+    .destroy_value = scv_avl_destroy,
+    .copy_value = scv_avl_copy};
+
+void grpc_subchannel_index_init(void) {
+  g_subchannel_index = gpr_avl_create(&subchannel_avl_vtable);
+  gpr_mu_init(&g_mu);
+}
+
+void grpc_subchannel_index_shutdown(void) {
+  gpr_mu_destroy(&g_mu);
+  gpr_avl_unref(g_subchannel_index);
+}
+
+grpc_subchannel *grpc_subchannel_index_find(grpc_exec_ctx *exec_ctx,
+                                            grpc_subchannel_key *key) {
+  enter_ctx(exec_ctx);
+
+  // Lock, and take a reference to the subchannel index.
+  // We don't need to do the search under a lock as avl's are immutable.
+  gpr_mu_lock(&g_mu);
+  gpr_avl index = gpr_avl_ref(g_subchannel_index);
+  gpr_mu_unlock(&g_mu);
+
+  grpc_subchannel *c =
+      GRPC_SUBCHANNEL_REF_FROM_WEAK_REF(gpr_avl_get(index, key), "index_find");
+  gpr_avl_unref(index);
+
+  leave_ctx(exec_ctx);
+  return c;
+}
+
+grpc_subchannel *grpc_subchannel_index_register(grpc_exec_ctx *exec_ctx,
+                                                grpc_subchannel_key *key,
+                                                grpc_subchannel *constructed) {
+  enter_ctx(exec_ctx);
+
+  grpc_subchannel *c = NULL;
+
+  while (c == NULL) {
+    // Compare and swap loop:
+    // - take a reference to the current index
+    gpr_mu_lock(&g_mu);
+    gpr_avl index = gpr_avl_ref(g_subchannel_index);
+    gpr_mu_unlock(&g_mu);
+
+    // - Check to see if a subchannel already exists
+    c = gpr_avl_get(index, key);
+    if (c != NULL) {
+      // yes -> we're done
+      GRPC_SUBCHANNEL_WEAK_UNREF(exec_ctx, constructed, "index_register");
+    } else {
+      // no -> update the avl and compare/swap
+      gpr_avl updated =
+          gpr_avl_add(gpr_avl_ref(index), subchannel_key_copy(key),
+                      GRPC_SUBCHANNEL_WEAK_REF(constructed, "index_register"));
+
+      // it may happen (but it's expected to be unlikely)
+      // that some other thread has changed the index:
+      // compare/swap here to check that, and retry as necessary
+      gpr_mu_lock(&g_mu);
+      if (index.root == g_subchannel_index.root) {
+        GPR_SWAP(gpr_avl, updated, g_subchannel_index);
+        c = constructed;
+      }
+      gpr_mu_unlock(&g_mu);
+
+      gpr_avl_unref(updated);
+    }
+    gpr_avl_unref(index);
+  }
+
+  leave_ctx(exec_ctx);
+
+  return c;
+}
+
+void grpc_subchannel_index_unregister(grpc_exec_ctx *exec_ctx,
+                                      grpc_subchannel_key *key,
+                                      grpc_subchannel *constructed) {
+  enter_ctx(exec_ctx);
+
+  bool done = false;
+  while (!done) {
+    // Compare and swap loop:
+    // - take a reference to the current index
+    gpr_mu_lock(&g_mu);
+    gpr_avl index = gpr_avl_ref(g_subchannel_index);
+    gpr_mu_unlock(&g_mu);
+
+    // Check to see if this key still refers to the previously
+    // registered subchannel
+    grpc_subchannel *c = gpr_avl_get(index, key);
+    if (c != constructed) {
+      gpr_avl_unref(index);
+      break;
+    }
+
+    // compare and swap the update (some other thread may have
+    // mutated the index behind us)
+    gpr_avl updated = gpr_avl_remove(gpr_avl_ref(index), key);
+
+    gpr_mu_lock(&g_mu);
+    if (index.root == g_subchannel_index.root) {
+      GPR_SWAP(gpr_avl, updated, g_subchannel_index);
+      done = true;
+    }
+    gpr_mu_unlock(&g_mu);
+
+    gpr_avl_unref(updated);
+    gpr_avl_unref(index);
+  }
+
+  leave_ctx(exec_ctx);
+}

src/core/client_config/subchannel_index.h

+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
+#define GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_INDEX_H
+
+#include "src/core/client_config/connector.h"
+#include "src/core/client_config/subchannel.h"
+
+/** \file Provides an index of active subchannels so that they can be
+    shared amongst channels */
+
+typedef struct grpc_subchannel_key grpc_subchannel_key;
+
+/** Create a key that can be used to uniquely identify a subchannel */
+grpc_subchannel_key *grpc_subchannel_key_create(grpc_connector *con,
+                                                grpc_subchannel_args *args);
+
+/** Destroy a subchannel key */
+void grpc_subchannel_key_destroy(grpc_exec_ctx *exec_ctx,
+                                 grpc_subchannel_key *key);
+
+/** Given a subchannel key, find the subchannel registered for it.
+    Returns NULL if no such channel exists.
+    Thread-safe. */
+grpc_subchannel *grpc_subchannel_index_find(grpc_exec_ctx *exec_ctx,
+                                            grpc_subchannel_key *key);
+
+/** Register a subchannel against a key.
+    Takes ownership of \a constructed.
+    Returns the registered subchannel. This may be different from
+    \a constructed in the case of a registration race. */
+grpc_subchannel *grpc_subchannel_index_register(grpc_exec_ctx *exec_ctx,
+                                                grpc_subchannel_key *key,
+                                                grpc_subchannel *constructed);
+
+/** Remove \a constructed as the registered subchannel for \a key. */
+void grpc_subchannel_index_unregister(grpc_exec_ctx *exec_ctx,
+                                      grpc_subchannel_key *key,
+                                      grpc_subchannel *constructed);
+
+/** Initialize the subchannel index (global) */
+void grpc_subchannel_index_init(void);
+/** Shutdown the subchannel index (global) */
+void grpc_subchannel_index_shutdown(void);
+
+#endif /* GRPC_INTERNAL_CORE_CLIENT_CONFIG_SUBCHANNEL_INDEX_H */

src/core/security/credentials.c

@@ -196,14 +196,21 @@ static void *server_credentials_pointer_arg_copy(void *p) {
   return grpc_server_credentials_ref(p);
 }
 
+static int server_credentials_pointer_cmp(void *a, void *b) {
+  return GPR_ICMP(a, b);
+}
+
+static const grpc_arg_pointer_vtable cred_ptr_vtable = {
+    server_credentials_pointer_arg_copy, server_credentials_pointer_arg_destroy,
+    server_credentials_pointer_cmp};
+
 grpc_arg grpc_server_credentials_to_arg(grpc_server_credentials *p) {
   grpc_arg arg;
   memset(&arg, 0, sizeof(grpc_arg));
   arg.type = GRPC_ARG_POINTER;
   arg.key = GRPC_SERVER_CREDENTIALS_ARG;
   arg.value.pointer.p = p;
-  arg.value.pointer.copy = server_credentials_pointer_arg_copy;
-  arg.value.pointer.destroy = server_credentials_pointer_arg_destroy;
+  arg.value.pointer.vtable = &cred_ptr_vtable;
   return arg;
 }
 

src/core/security/security_connector.c

@@ -202,12 +202,17 @@ static void *connector_pointer_arg_copy(void *p) {
   return GRPC_SECURITY_CONNECTOR_REF(p, "connector_pointer_arg");
 }
 
+static int connector_pointer_cmp(void *a, void *b) { return GPR_ICMP(a, b); }
+
+static const grpc_arg_pointer_vtable connector_pointer_vtable = {
+    connector_pointer_arg_copy, connector_pointer_arg_destroy,
+    connector_pointer_cmp};
+
 grpc_arg grpc_security_connector_to_arg(grpc_security_connector *sc) {
   grpc_arg result;
   result.type = GRPC_ARG_POINTER;
   result.key = GRPC_SECURITY_CONNECTOR_ARG;
-  result.value.pointer.destroy = connector_pointer_arg_destroy;
-  result.value.pointer.copy = connector_pointer_arg_copy;
+  result.value.pointer.vtable = &connector_pointer_vtable;
   result.value.pointer.p = sc;
   return result;
 }