Merge branch 'master' into move-method-handler

6 years ago · de2006d3e1
parent 29bb3ef973 21cf17aacf
commit de2006d3e1
145 changed files with 2049 additions and 1733 deletions
--- a/.github/ISSUE_TEMPLATE/bug_report.md
+++ b/.github/ISSUE_TEMPLATE/bug_report.md
@ -2,7 +2,7 @@
 name: Report a bug
 about: Create a report to help us improve
 labels: kind/bug, priority/P2
-assignees: AspirinSJL
+assignees: mhaidrygoog

 ---

--- a/.github/ISSUE_TEMPLATE/cleanup_request.md
+++ b/.github/ISSUE_TEMPLATE/cleanup_request.md
@ -2,7 +2,7 @@
 name: Request a cleanup
 about: Suggest a cleanup in our repository
 labels: kind/internal cleanup
-assignees: AspirinSJL
+assignees: mhaidrygoog

 ---

--- a/.github/ISSUE_TEMPLATE/feature_request.md
+++ b/.github/ISSUE_TEMPLATE/feature_request.md
@ -2,7 +2,7 @@
 name: Request a feature
 about: Suggest an idea for this project
 labels: kind/enhancement
-assignees: AspirinSJL
+assignees: mhaidrygoog

 ---

--- a/.github/pull_request_template.md
+++ b/.github/pull_request_template.md
@ -8,4 +8,4 @@ If you know who should review your pull request, please remove the mentioning be

 -->

-@AspirinSJL
+@mhaidrygoog
--- a/.gitignore
+++ b/.gitignore
@ -140,6 +140,7 @@ bm_*.json

 # Visual Studio Code artifacts
 .vscode/*
+.history/

 # Clion artifacts
 cmake-build-debug/
--- a/9
+++ b/9
@ -73,6 +73,11 @@ config_setting(
    values = {"cpu": "darwin"},
 )

+config_setting(
+    name = "grpc_use_cpp_std_lib",
+    values = {"define": "GRPC_USE_CPP_STD_LIB=1"},
+)
+
 # This should be updated along with build.yaml
 g_stands_for = "ganges"

@ -1216,6 +1221,7 @@ grpc_cc_library(
        "grpc_client_channel",
        "grpc_lb_upb",
        "grpc_resolver_fake",
+        "grpc_transport_chttp2_client_insecure",
    ],
 )

@ -1242,6 +1248,7 @@ grpc_cc_library(
        "grpc_lb_upb",
        "grpc_resolver_fake",
        "grpc_secure",
+        "grpc_transport_chttp2_client_secure",
    ],
 )

@ -1265,6 +1272,7 @@ grpc_cc_library(
        "grpc_base",
        "grpc_client_channel",
        "grpc_resolver_fake",
+        "grpc_transport_chttp2_client_insecure",
    ],
 )

@ -1289,6 +1297,7 @@ grpc_cc_library(
        "grpc_client_channel",
        "grpc_resolver_fake",
        "grpc_secure",
+        "grpc_transport_chttp2_client_secure",
    ],
 )

--- a/BUILDING.md
+++ b/BUILDING.md
@ -12,7 +12,7 @@ gRPC C++ - Building from source
 If you plan to build from source and run tests, install the following as well:
 ```sh
 $ [sudo] apt-get install libgflags-dev libgtest-dev
- $ [sudo] apt-get install clang libc++-dev
+ $ [sudo] apt-get install clang-5.0 libc++-dev
 ```
 Lastly, see the Protoc section below if you do not yet have the protoc compiler installed.

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@ -96,8 +96,6 @@ endif()

 set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)

-add_definitions(-DPB_FIELD_32BIT)
-
 if (MSVC)
  include(cmake/msvc_static_runtime.cmake)
  add_definitions(-D_WIN32_WINNT=0x600 -D_SCL_SECURE_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS -D_WINSOCK_DEPRECATED_NO_WARNINGS)
--- a/4
+++ b/4
@ -354,7 +354,7 @@ CXXFLAGS += -stdlib=libc++
 LDFLAGS += -framework CoreFoundation
 endif
 CXXFLAGS += -Wnon-virtual-dtor
-CPPFLAGS += -g -Wall -Wextra -Werror $(W_NO_UNKNOWN_WARNING_OPTION) -Wno-long-long -Wno-unused-parameter -Wno-deprecated-declarations -Wno-sign-conversion -Wno-shadow -Wno-conversion -Wno-implicit-fallthrough -Wno-sign-compare -Wno-missing-field-initializers -Wno-maybe-uninitialized -DPB_FIELD_32BIT -DOSATOMIC_USE_INLINED=1 -Ithird_party/upb -Isrc/core/ext/upb-generated
+CPPFLAGS += -g -Wall -Wextra -Werror $(W_NO_UNKNOWN_WARNING_OPTION) -Wno-long-long -Wno-unused-parameter -Wno-deprecated-declarations -Wno-sign-conversion -Wno-shadow -Wno-conversion -Wno-implicit-fallthrough -Wno-sign-compare -Wno-missing-field-initializers -Wno-maybe-uninitialized -DOSATOMIC_USE_INLINED=1 -Ithird_party/upb -Isrc/core/ext/upb-generated
 COREFLAGS += -fno-rtti -fno-exceptions
 LDFLAGS += -g

@ -451,7 +451,7 @@ USE_BUILT_PROTOC = false
 endif

 GTEST_LIB = -Ithird_party/googletest/googletest/include -Ithird_party/googletest/googletest third_party/googletest/googletest/src/gtest-all.cc -Ithird_party/googletest/googlemock/include -Ithird_party/googletest/googlemock third_party/googletest/googlemock/src/gmock-all.cc
-GTEST_LIB += -lgflags
+GTEST_LIB += -lgflags -std=c++11
 ifeq ($(V),1)
 E = @:
 Q =
--- a/1
+++ b/1
@ -105,6 +105,7 @@ task 'dlls' do
    env_comp = "CC=#{opt[:cross]}-gcc "
    env_comp += "CXX=#{opt[:cross]}-g++ "
    env_comp += "LD=#{opt[:cross]}-gcc "
+    env_comp += "LDXX=#{opt[:cross]}-g++ "
    docker_for_windows "gem update --system --no-document && #{env} #{env_comp} make -j #{out} && #{opt[:cross]}-strip -x -S #{out} && cp #{out} #{opt[:out]}"
  end

--- a/bazel/grpc_build_system.bzl
+++ b/bazel/grpc_build_system.bzl
@ -99,6 +99,9 @@ def grpc_cc_library(
                      "//:grpc_allow_exceptions": ["GRPC_ALLOW_EXCEPTIONS=1"],
                      "//:grpc_disallow_exceptions": ["GRPC_ALLOW_EXCEPTIONS=0"],
                      "//conditions:default": [],
+                  }) + select({
+                      "//:grpc_use_cpp_std_lib": ["GRPC_USE_CPP_STD_LIB=1"],
+                      "//conditions:default": [],
                  }),
        hdrs = hdrs + public_hdrs,
        deps = deps + _get_external_deps(external_deps),
--- a/bazel/grpc_deps.bzl
+++ b/bazel/grpc_deps.bzl
@ -62,7 +62,7 @@ def grpc_deps():
        name = "gtest",
        actual = "@com_github_google_googletest//:gtest",
    )
-
+    
    native.bind(
        name = "benchmark",
        actual = "@com_github_google_benchmark//:benchmark",
@ -127,9 +127,17 @@ def grpc_deps():
    if "com_github_google_googletest" not in native.existing_rules():
        http_archive(
            name = "com_github_google_googletest",
-            sha256 = "d0d447b4feeedca837a0d46a289d4223089b32ac2f84545fa4982755cc8919be",
-            strip_prefix = "googletest-2fe3bd994b3189899d93f1d5a881e725e046fdc2",
-            url = "https://github.com/google/googletest/archive/2fe3bd994b3189899d93f1d5a881e725e046fdc2.tar.gz",
+            sha256 = "443d383db648ebb8e391382c0ab63263b7091d03197f304390baac10f178a468",
+            strip_prefix = "googletest-c9ccac7cb7345901884aabf5d1a786cfa6e2f397",
+            url = "https://github.com/google/googletest/archive/c9ccac7cb7345901884aabf5d1a786cfa6e2f397.tar.gz", # 2019-08-19
+        )
+
+    if "rules_cc" not in native.existing_rules():
+        http_archive(
+            name = "rules_cc",
+            sha256 = "35f2fb4ea0b3e61ad64a369de284e4fbbdcdba71836a5555abb5e194cf119509",
+            strip_prefix = "rules_cc-624b5d59dfb45672d4239422fa1e3de1822ee110",
+            url = "https://github.com/bazelbuild/rules_cc/archive/624b5d59dfb45672d4239422fa1e3de1822ee110.tar.gz", #2019-08-15
        )

    if "com_github_gflags_gflags" not in native.existing_rules():
--- a/bazel/python_rules.bzl
+++ b/bazel/python_rules.bzl
@ -61,22 +61,22 @@ _generate_pb2_src = rule(

 def py_proto_library(
        name,
-        srcs,
+        deps,
        **kwargs):
    """Generate python code for a protobuf.

    Args:
      name: The name of the target.
-      srcs: A list of proto_library dependencies. Must contain a single element.
+      deps: A list of proto_library dependencies. Must contain a single element.
    """
    codegen_target = "_{}_codegen".format(name)
-    if len(srcs) != 1:
+    if len(deps) != 1:
        fail("Can only compile a single proto at a time.")


    _generate_pb2_src(
        name = codegen_target,
-        deps = srcs,
+        deps = deps,
        **kwargs
    )

--- a/bazel/test/python_test_repo/BUILD
+++ b/bazel/test/python_test_repo/BUILD
@ -29,7 +29,7 @@ proto_library(

 py_proto_library(
    name = "helloworld_py_pb2",
-    srcs = [":helloworld_proto"],
+    deps = [":helloworld_proto"],
 )

 py_grpc_library(
@ -40,12 +40,12 @@ py_grpc_library(

 py_proto_library(
    name = "duration_py_pb2",
-    srcs = ["@com_google_protobuf//:duration_proto"],
+    deps = ["@com_google_protobuf//:duration_proto"],
 )

 py_proto_library(
    name = "timestamp_py_pb2",
-    srcs = ["@com_google_protobuf//:timestamp_proto"],
+    deps = ["@com_google_protobuf//:timestamp_proto"],
 )

 py_test(
--- a/build.yaml
+++ b/build.yaml
@ -6201,8 +6201,7 @@ defaults:
    CPPFLAGS: -g -Wall -Wextra -Werror $(W_NO_UNKNOWN_WARNING_OPTION) -Wno-long-long
      -Wno-unused-parameter -Wno-deprecated-declarations -Wno-sign-conversion -Wno-shadow
      -Wno-conversion -Wno-implicit-fallthrough -Wno-sign-compare -Wno-missing-field-initializers
-      -Wno-maybe-uninitialized -DPB_FIELD_32BIT -DOSATOMIC_USE_INLINED=1 -Ithird_party/upb
-      -Isrc/core/ext/upb-generated
+      -Wno-maybe-uninitialized -DOSATOMIC_USE_INLINED=1 -Ithird_party/upb -Isrc/core/ext/upb-generated
    CXXFLAGS: -Wnon-virtual-dtor
    LDFLAGS: -g
  zlib:
--- a/config.m4
+++ b/config.m4
@ -14,8 +14,8 @@ if test "$PHP_GRPC" != "no"; then

  LIBS="-lpthread $LIBS"

-  CFLAGS="-Wall -Werror -Wno-parentheses-equality -Wno-unused-value -std=c11 -g -O2 -D PB_FIELD_32BIT=1"
-  CXXFLAGS="-std=c++11 -fno-exceptions -fno-rtti -g -O2 -D PB_FIELD_32BIT=1"
+  CFLAGS="-Wall -Werror -Wno-parentheses-equality -Wno-unused-value -std=c11 -g -O2"
+  CXXFLAGS="-std=c++11 -fno-exceptions -fno-rtti -g -O2"
  GRPC_SHARED_LIBADD="-lpthread $GRPC_SHARED_LIBADD"
  PHP_REQUIRE_CXX()
  PHP_ADD_LIBRARY(pthread)
--- a/config.w32
+++ b/config.w32
@ -706,7 +706,6 @@ if (PHP_GRPC != "no") {
  EXTENSION("grpc", grpc_source, null,
    "/DOPENSSL_NO_ASM /D_GNU_SOURCE /DWIN32_LEAN_AND_MEAN "+
    "/D_HAS_EXCEPTIONS=0 /DNOMINMAX /DGRPC_ARES=0 /D_WIN32_WINNT=0x600 "+
-    "/DPB_FIELD_32BIT "+
    "/I"+configure_module_dirname+" "+
    "/I"+configure_module_dirname+"\\include "+
    "/I"+configure_module_dirname+"\\src\\core\\ext\\upb-generated "+
--- a/examples/BUILD
+++ b/examples/BUILD
@ -67,7 +67,7 @@ proto_library(

 py_proto_library(
    name = "helloworld_py_pb2",
-    srcs = [":protos/helloworld_proto"],
+    deps = [":protos/helloworld_proto"],
 )

 py_grpc_library(
--- a/examples/python/cancellation/BUILD.bazel
+++ b/examples/python/cancellation/BUILD.bazel
@ -26,7 +26,7 @@ proto_library(

 py_proto_library(
    name = "hash_name_py_pb2",
-    srcs = [":hash_name_proto"],
+    deps = [":hash_name_proto"],
 )

 py_grpc_library(
--- a/examples/python/multiprocessing/BUILD
+++ b/examples/python/multiprocessing/BUILD
@ -23,7 +23,7 @@ proto_library(

 py_proto_library(
    name = "prime_proto_pb2",
-    srcs = [":prime_proto"],
+    deps = [":prime_proto"],
 )

 py_grpc_library(
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@ -56,7 +56,7 @@ Pod::Spec.new do |s|
  s.pod_target_xcconfig = {
    'HEADER_SEARCH_PATHS' => '"$(inherited)" "$(PODS_TARGET_SRCROOT)/include"',
    'USER_HEADER_SEARCH_PATHS' => '"$(PODS_TARGET_SRCROOT)"',
-    'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1" "PB_NO_PACKED_STRUCTS=1"',
+    'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1"',
    'CLANG_WARN_STRICT_PROTOTYPES' => 'NO',
    'CLANG_WARN_DOCUMENTATION_COMMENTS' => 'NO',

--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@ -91,12 +91,12 @@ Pod::Spec.new do |s|
    # build.
    'USE_HEADERMAP' => 'NO',
    'ALWAYS_SEARCH_USER_PATHS' => 'NO',
-    'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1" "PB_NO_PACKED_STRUCTS=1"',
+    'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1"',
    'CLANG_WARN_STRICT_PROTOTYPES' => 'NO',
  }

  s.default_subspecs = 'Interface', 'Implementation'
-  s.compiler_flags = '-DGRPC_ARES=0', '-DPB_FIELD_32BIT'
+  s.compiler_flags = '-DGRPC_ARES=0'
  s.libraries = 'c++'

  # Like many other C libraries, gRPC-Core has its public headers under `include/<libname>/` and its
--- a/grpc.gyp
+++ b/grpc.gyp
@ -66,7 +66,6 @@
      '-Wno-sign-compare',
      '-Wno-missing-field-initializers',
      '-Wno-maybe-uninitialized',
-      '-DPB_FIELD_32BIT',
      '-DOSATOMIC_USE_INLINED=1',
      '-Ithird_party/upb',
      '-Isrc/core/ext/upb-generated',
@ -155,7 +154,6 @@
            '-Wno-sign-compare',
            '-Wno-missing-field-initializers',
            '-Wno-maybe-uninitialized',
-            '-DPB_FIELD_32BIT',
            '-DOSATOMIC_USE_INLINED=1',
            '-Ithird_party/upb',
            '-Isrc/core/ext/upb-generated',
@ -176,7 +174,6 @@
            '-Wno-sign-compare',
            '-Wno-missing-field-initializers',
            '-Wno-maybe-uninitialized',
-            '-DPB_FIELD_32BIT',
            '-DOSATOMIC_USE_INLINED=1',
            '-Ithird_party/upb',
            '-Isrc/core/ext/upb-generated',
--- a/include/grpc/impl/codegen/port_platform.h
+++ b/include/grpc/impl/codegen/port_platform.h
@ -27,6 +27,15 @@
 *  - some syscalls to be made directly
 */

+/*
+ * Defines GRPC_USE_CPP_STD_LIB to use standard C++ library instead of
+ * in-house library if possible. (e.g. std::map)
+ */
+#ifndef GRPC_USE_CPP_STD_LIB
+/* Default value will be 1 once all tests become green. */
+#define GRPC_USE_CPP_STD_LIB 0
+#endif
+
 /* Get windows.h included everywhere (we need it) */
 #if defined(_WIN64) || defined(WIN64) || defined(_WIN32) || defined(WIN32)
 #ifndef WIN32_LEAN_AND_MEAN
--- a/setup.py
+++ b/setup.py
@ -161,7 +161,6 @@ if EXTRA_ENV_COMPILE_ARGS is None:
    EXTRA_ENV_COMPILE_ARGS += ' -std=gnu99 -fvisibility=hidden -fno-wrapv -fno-exceptions'
  elif "darwin" in sys.platform:
    EXTRA_ENV_COMPILE_ARGS += ' -stdlib=libc++ -fvisibility=hidden -fno-wrapv -fno-exceptions'
-EXTRA_ENV_COMPILE_ARGS += ' -DPB_FIELD_32BIT'

 if EXTRA_ENV_LINK_ARGS is None:
  EXTRA_ENV_LINK_ARGS = ''
--- a/src/core/ext/filters/client_channel/client_channel.cc
+++ b/src/core/ext/filters/client_channel/client_channel.cc
@ -1318,11 +1318,6 @@ class ChannelData::ClientChannelControlHelper
        chand_, subchannel, std::move(health_check_service_name));
  }

-  grpc_channel* CreateChannel(const char* target,
-                              const grpc_channel_args& args) override {
-    return chand_->client_channel_factory_->CreateChannel(target, &args);
-  }
-
  void UpdateState(
      grpc_connectivity_state state,
      UniquePtr<LoadBalancingPolicy::SubchannelPicker> picker) override {
@ -1345,11 +1340,11 @@ class ChannelData::ClientChannelControlHelper
  // No-op -- we should never get this from ResolvingLoadBalancingPolicy.
  void RequestReresolution() override {}

-  void AddTraceEvent(TraceSeverity severity, const char* message) override {
+  void AddTraceEvent(TraceSeverity severity, StringView message) override {
    if (chand_->channelz_node_ != nullptr) {
      chand_->channelz_node_->AddTraceEvent(
          ConvertSeverityEnum(severity),
-          grpc_slice_from_copied_string(message));
+          grpc_slice_from_copied_buffer(message.data(), message.size()));
    }
  }

@ -3168,8 +3163,8 @@ void CallData::AddRetriableSendInitialMetadataOp(
    SubchannelCallRetryState* retry_state,
    SubchannelCallBatchData* batch_data) {
  // Maps the number of retries to the corresponding metadata value slice.
-  static const grpc_slice* retry_count_strings[] = {
-      &GRPC_MDSTR_1, &GRPC_MDSTR_2, &GRPC_MDSTR_3, &GRPC_MDSTR_4};
+  const grpc_slice* retry_count_strings[] = {&GRPC_MDSTR_1, &GRPC_MDSTR_2,
+                                             &GRPC_MDSTR_3, &GRPC_MDSTR_4};
  // We need to make a copy of the metadata batch for each attempt, since
  // the filters in the subchannel stack may modify this batch, and we don't
  // want those modifications to be passed forward to subsequent attempts.
@ -3730,8 +3725,8 @@ const char* PickResultTypeName(
      return "COMPLETE";
    case LoadBalancingPolicy::PickResult::PICK_QUEUE:
      return "QUEUE";
-    case LoadBalancingPolicy::PickResult::PICK_TRANSIENT_FAILURE:
-      return "TRANSIENT_FAILURE";
+    case LoadBalancingPolicy::PickResult::PICK_FAILED:
+      return "FAILED";
  }
  GPR_UNREACHABLE_CODE(return "UNKNOWN");
 }
@ -3792,7 +3787,7 @@ void CallData::StartPickLocked(void* arg, grpc_error* error) {
            result.subchannel.get(), grpc_error_string(result.error));
  }
  switch (result.type) {
-    case LoadBalancingPolicy::PickResult::PICK_TRANSIENT_FAILURE: {
+    case LoadBalancingPolicy::PickResult::PICK_FAILED: {
      // If we're shutting down, fail all RPCs.
      grpc_error* disconnect_error = chand->disconnect_error();
      if (disconnect_error != GRPC_ERROR_NONE) {
--- a/src/core/ext/filters/client_channel/client_channel_factory.h
+++ b/src/core/ext/filters/client_channel/client_channel_factory.h
@ -36,10 +36,6 @@ class ClientChannelFactory {
  virtual Subchannel* CreateSubchannel(const grpc_channel_args* args)
      GRPC_ABSTRACT;

-  // Creates a channel for the specified target with the specified args.
-  virtual grpc_channel* CreateChannel(
-      const char* target, const grpc_channel_args* args) GRPC_ABSTRACT;
-
  // Returns a channel arg containing the specified factory.
  static grpc_arg CreateChannelArg(ClientChannelFactory* factory);

--- a/src/core/ext/filters/client_channel/http_proxy.cc
+++ b/src/core/ext/filters/client_channel/http_proxy.cc
@ -47,10 +47,12 @@ static char* get_http_proxy_server(char** user_cred) {
  char* proxy_name = nullptr;
  char** authority_strs = nullptr;
  size_t authority_nstrs;
-  /* Prefer using 'https_proxy'. Fallback on 'http_proxy' if it is not set. The
+  /* Prefer using 'grpc_proxy'. Fallback on 'http_proxy' if it is not set.
+   * Also prefer using 'https_proxy' with fallback on 'http_proxy'. The
   * fallback behavior can be removed if there's a demand for it.
   */
-  char* uri_str = gpr_getenv("https_proxy");
+  char* uri_str = gpr_getenv("grpc_proxy");
+  if (uri_str == nullptr) uri_str = gpr_getenv("https_proxy");
  if (uri_str == nullptr) uri_str = gpr_getenv("http_proxy");
  if (uri_str == nullptr) return nullptr;
  grpc_uri* uri = grpc_uri_parse(uri_str, false /* suppress_errors */);
@ -122,7 +124,9 @@ static bool proxy_mapper_map_name(grpc_proxy_mapper* mapper,
            server_uri);
    goto no_use_proxy;
  }
-  no_proxy_str = gpr_getenv("no_proxy");
+  /* Prefer using 'no_grpc_proxy'. Fallback on 'no_proxy' if it is not set. */
+  no_proxy_str = gpr_getenv("no_grpc_proxy");
+  if (no_proxy_str == nullptr) no_proxy_str = gpr_getenv("no_proxy");
  if (no_proxy_str != nullptr) {
    static const char* NO_PROXY_SEPARATOR = ",";
    bool use_proxy = true;
--- a/src/core/ext/filters/client_channel/lb_policy.cc
+++ b/src/core/ext/filters/client_channel/lb_policy.cc
@ -129,7 +129,7 @@ void LoadBalancingPolicy::QueuePicker::CallExitIdle(void* arg,
 LoadBalancingPolicy::PickResult
 LoadBalancingPolicy::TransientFailurePicker::Pick(PickArgs args) {
  PickResult result;
-  result.type = PickResult::PICK_TRANSIENT_FAILURE;
+  result.type = PickResult::PICK_FAILED;
  result.error = GRPC_ERROR_REF(error_);
  return result;
 }
--- a/src/core/ext/filters/client_channel/lb_policy.h
+++ b/src/core/ext/filters/client_channel/lb_policy.h
@ -42,15 +42,15 @@ extern DebugOnlyTraceFlag grpc_trace_lb_policy_refcount;
 ///
 /// Channel: An abstraction that manages connections to backend servers
 ///   on behalf of a client application.  The application creates a channel
-///   for a given server name and then sends RPCs on it, and the channel
-///   figures out which backend server to send each RPC to.  A channel
+///   for a given server name and then sends calls (RPCs) on it, and the
+///   channel figures out which backend server to send each call to.  A channel
 ///   contains a resolver, a load balancing policy (or a tree of LB policies),
 ///   and a set of one or more subchannels.
 ///
 /// Subchannel: A subchannel represents a connection to one backend server.
 ///   The LB policy decides which subchannels to create, manages the
 ///   connectivity state of those subchannels, and decides which subchannel
-///   to send any given RPC to.
+///   to send any given call to.
 ///
 /// Resolver: A plugin that takes a gRPC server URI and resolves it to a
 ///   list of one or more addresses and a service config, as described
@ -59,12 +59,12 @@ extern DebugOnlyTraceFlag grpc_trace_lb_policy_refcount;
 ///
 /// Load Balancing (LB) Policy: A plugin that takes a list of addresses
 ///   from the resolver, maintains and manages a subchannel for each
-///   backend address, and decides which subchannel to send each RPC on.
+///   backend address, and decides which subchannel to send each call on.
 ///   An LB policy has two parts:
 ///   - A LoadBalancingPolicy, which deals with the control plane work of
 ///     managing subchannels.
 ///   - A SubchannelPicker, which handles the data plane work of
-///     determining which subchannel a given RPC should be sent on.
+///     determining which subchannel a given call should be sent on.

 /// LoadBalacingPolicy API.
 ///
@ -78,6 +78,7 @@ extern DebugOnlyTraceFlag grpc_trace_lb_policy_refcount;
 class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
 public:
  /// Interface for accessing per-call state.
+  /// Implemented by the client channel and used by the SubchannelPicker.
  class CallState {
   public:
    CallState() = default;
@ -93,6 +94,7 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
  };

  /// Interface for accessing metadata.
+  /// Implemented by the client channel and used by the SubchannelPicker.
  class MetadataInterface {
   public:
    // Implementations whose iterators fit in intptr_t may internally
@ -123,7 +125,7 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
    GRPC_ABSTRACT_BASE_CLASS
  };

-  /// Arguments used when picking a subchannel for an RPC.
+  /// Arguments used when picking a subchannel for a call.
  struct PickArgs {
    /// Initial metadata associated with the picking call.
    /// The LB policy may use the existing metadata to influence its routing
@ -135,24 +137,23 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
    CallState* call_state;
  };

-  /// The result of picking a subchannel for an RPC.
+  /// The result of picking a subchannel for a call.
  struct PickResult {
    enum ResultType {
-      /// Pick complete.  If connected_subchannel is non-null, client channel
-      /// can immediately proceed with the call on connected_subchannel;
-      /// otherwise, call should be dropped.
+      /// Pick complete.  If \a subchannel is non-null, the client channel
+      /// will immediately proceed with the call on that subchannel;
+      /// otherwise, it will drop the call.
      PICK_COMPLETE,
      /// Pick cannot be completed until something changes on the control
-      /// plane.  Client channel will queue the pick and try again the
+      /// plane.  The client channel will queue the pick and try again the
      /// next time the picker is updated.
      PICK_QUEUE,
-      /// LB policy is in transient failure.  If the pick is wait_for_ready,
-      /// client channel will wait for the next picker and try again;
-      /// otherwise, the call will be failed immediately (although it may
-      /// be retried if the client channel is configured to do so).
-      /// The Pick() method will set its error parameter if this value is
-      /// returned.
-      PICK_TRANSIENT_FAILURE,
+      /// Pick failed.  If the call is wait_for_ready, the client channel
+      /// will wait for the next picker and try again; otherwise, it
+      /// will immediately fail the call with the status indicated via
+      /// \a error (although the call may be retried if the client channel
+      /// is configured to do so).
+      PICK_FAILED,
    };
    ResultType type;

@ -160,14 +161,14 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
    /// subchannel, or nullptr if the LB policy decides to drop the call.
    RefCountedPtr<SubchannelInterface> subchannel;

-    /// Used only if type is PICK_TRANSIENT_FAILURE.
-    /// Error to be set when returning a transient failure.
+    /// Used only if type is PICK_FAILED.
+    /// Error to be set when returning a failure.
    // TODO(roth): Replace this with something similar to grpc::Status,
    // so that we don't expose grpc_error to this API.
    grpc_error* error = GRPC_ERROR_NONE;

    /// Used only if type is PICK_COMPLETE.
-    /// Callback set by lb policy to be notified of trailing metadata.
+    /// Callback set by LB policy to be notified of trailing metadata.
    /// The user_data argument will be set to the
    /// recv_trailing_metadata_ready_user_data field.
    /// recv_trailing_metadata will be set to the metadata, which may be
@ -184,11 +185,12 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
  };

  /// A subchannel picker is the object used to pick the subchannel to
-  /// use for a given RPC.
+  /// use for a given call.  This is implemented by the LB policy and
+  /// used by the client channel to perform picks.
  ///
  /// Pickers are intended to encapsulate all of the state and logic
  /// needed on the data plane (i.e., to actually process picks for
-  /// individual RPCs sent on the channel) while excluding all of the
+  /// individual calls sent on the channel) while excluding all of the
  /// state and logic needed on the control plane (i.e., resolver
  /// updates, connectivity state notifications, etc); the latter should
  /// live in the LB policy object itself.
@ -206,8 +208,8 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
    GRPC_ABSTRACT_BASE_CLASS
  };

-  /// A proxy object used by the LB policy to communicate with the client
-  /// channel.
+  /// A proxy object implemented by the client channel and used by the
+  /// LB policy to communicate with the channel.
  // TODO(juanlishen): Consider adding a mid-layer subclass that helps handle
  // things like swapping in pending policy when it's ready. Currently, we are
  // duplicating the logic in many subclasses.
@ -220,12 +222,6 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
    virtual RefCountedPtr<SubchannelInterface> CreateSubchannel(
        const grpc_channel_args& args) GRPC_ABSTRACT;

-    /// Creates a channel with the specified target and channel args.
-    /// This can be used in cases where the LB policy needs to create a
-    /// channel for its own use (e.g., to talk to an external load balancer).
-    virtual grpc_channel* CreateChannel(
-        const char* target, const grpc_channel_args& args) GRPC_ABSTRACT;
-
    /// Sets the connectivity state and returns a new picker to be used
    /// by the client channel.
    virtual void UpdateState(grpc_connectivity_state state,
@ -235,10 +231,9 @@ class LoadBalancingPolicy : public InternallyRefCounted<LoadBalancingPolicy> {
    virtual void RequestReresolution() GRPC_ABSTRACT;

    /// Adds a trace message associated with the channel.
-    /// Does NOT take ownership of \a message.
    enum TraceSeverity { TRACE_INFO, TRACE_WARNING, TRACE_ERROR };
    virtual void AddTraceEvent(TraceSeverity severity,
-                               const char* message) GRPC_ABSTRACT;
+                               StringView message) GRPC_ABSTRACT;

    GRPC_ABSTRACT_BASE_CLASS
  };
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc
@ -293,12 +293,10 @@ class GrpcLb : public LoadBalancingPolicy {

    RefCountedPtr<SubchannelInterface> CreateSubchannel(
        const grpc_channel_args& args) override;
-    grpc_channel* CreateChannel(const char* target,
-                                const grpc_channel_args& args) override;
    void UpdateState(grpc_connectivity_state state,
                     UniquePtr<SubchannelPicker> picker) override;
    void RequestReresolution() override;
-    void AddTraceEvent(TraceSeverity severity, const char* message) override;
+    void AddTraceEvent(TraceSeverity severity, StringView message) override;

    void set_child(LoadBalancingPolicy* child) { child_ = child; }

@ -652,15 +650,6 @@ RefCountedPtr<SubchannelInterface> GrpcLb::Helper::CreateSubchannel(
  return parent_->channel_control_helper()->CreateSubchannel(args);
 }

-grpc_channel* GrpcLb::Helper::CreateChannel(const char* target,
-                                            const grpc_channel_args& args) {
-  if (parent_->shutting_down_ ||
-      (!CalledByPendingChild() && !CalledByCurrentChild())) {
-    return nullptr;
-  }
-  return parent_->channel_control_helper()->CreateChannel(target, args);
-}
-
 void GrpcLb::Helper::UpdateState(grpc_connectivity_state state,
                                 UniquePtr<SubchannelPicker> picker) {
  if (parent_->shutting_down_) return;
@ -756,8 +745,7 @@ void GrpcLb::Helper::RequestReresolution() {
  }
 }

-void GrpcLb::Helper::AddTraceEvent(TraceSeverity severity,
-                                   const char* message) {
+void GrpcLb::Helper::AddTraceEvent(TraceSeverity severity, StringView message) {
  if (parent_->shutting_down_ ||
      (!CalledByPendingChild() && !CalledByCurrentChild())) {
    return;
@ -1276,7 +1264,7 @@ grpc_channel_args* BuildBalancerChannelArgs(
      // the LB channel.
      GRPC_ARG_FAKE_RESOLVER_RESPONSE_GENERATOR,
      // The LB channel should use the authority indicated by the target
-      // authority table (see \a grpc_lb_policy_grpclb_modify_lb_channel_args),
+      // authority table (see \a ModifyGrpclbBalancerChannelArgs),
      // as opposed to the authority from the parent channel.
      GRPC_ARG_DEFAULT_AUTHORITY,
      // Just as for \a GRPC_ARG_DEFAULT_AUTHORITY, the LB channel should be
@ -1312,7 +1300,7 @@ grpc_channel_args* BuildBalancerChannelArgs(
      args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), args_to_add.data(),
      args_to_add.size());
  // Make any necessary modifications for security.
-  return grpc_lb_policy_grpclb_modify_lb_channel_args(addresses, new_args);
+  return ModifyGrpclbBalancerChannelArgs(addresses, new_args);
 }

 //
@ -1488,8 +1476,7 @@ void GrpcLb::ProcessAddressesAndChannelArgsLocked(
  if (lb_channel_ == nullptr) {
    char* uri_str;
    gpr_asprintf(&uri_str, "fake:///%s", server_name_);
-    lb_channel_ =
-        channel_control_helper()->CreateChannel(uri_str, *lb_channel_args);
+    lb_channel_ = CreateGrpclbBalancerChannel(uri_str, *lb_channel_args);
    GPR_ASSERT(lb_channel_ != nullptr);
    gpr_free(uri_str);
  }
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.cc
@ -18,9 +18,20 @@

 #include <grpc/support/port_platform.h>

+#include <grpc/grpc.h>
+
 #include "src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h"

-grpc_channel_args* grpc_lb_policy_grpclb_modify_lb_channel_args(
-    const grpc_core::ServerAddressList& addresses, grpc_channel_args* args) {
+namespace grpc_core {
+
+grpc_channel_args* ModifyGrpclbBalancerChannelArgs(
+    const ServerAddressList& addresses, grpc_channel_args* args) {
  return args;
 }
+
+grpc_channel* CreateGrpclbBalancerChannel(const char* target_uri,
+                                          const grpc_channel_args& args) {
+  return grpc_insecure_channel_create(target_uri, &args, nullptr);
+}
+
+}  // namespace grpc_core
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h
@ -25,14 +25,21 @@

 #include "src/core/ext/filters/client_channel/server_address.h"

+namespace grpc_core {
+
 /// Makes any necessary modifications to \a args for use in the grpclb
 /// balancer channel.
 ///
 /// Takes ownership of \a args.
 ///
 /// Caller takes ownership of the returned args.
-grpc_channel_args* grpc_lb_policy_grpclb_modify_lb_channel_args(
-    const grpc_core::ServerAddressList& addresses, grpc_channel_args* args);
+grpc_channel_args* ModifyGrpclbBalancerChannelArgs(
+    const ServerAddressList& addresses, grpc_channel_args* args);
+
+grpc_channel* CreateGrpclbBalancerChannel(const char* target_uri,
+                                          const grpc_channel_args& args);
+
+}  // namespace grpc_core

 #endif /* GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_LB_POLICY_GRPCLB_GRPCLB_CHANNEL_H \
        */
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel_secure.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel_secure.cc
@ -22,6 +22,7 @@

 #include <string.h>

+#include <grpc/grpc_security.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/string_util.h>

@ -35,6 +36,7 @@
 #include "src/core/lib/slice/slice_internal.h"

 namespace grpc_core {
+
 namespace {

 int BalancerNameCmp(const grpc_core::UniquePtr<char>& a,
@ -65,37 +67,53 @@ RefCountedPtr<TargetAuthorityTable> CreateTargetAuthorityTable(
 }

 }  // namespace
-}  // namespace grpc_core

-grpc_channel_args* grpc_lb_policy_grpclb_modify_lb_channel_args(
-    const grpc_core::ServerAddressList& addresses, grpc_channel_args* args) {
-  const char* args_to_remove[1];
-  size_t num_args_to_remove = 0;
-  grpc_arg args_to_add[2];
-  size_t num_args_to_add = 0;
+grpc_channel_args* ModifyGrpclbBalancerChannelArgs(
+    const ServerAddressList& addresses, grpc_channel_args* args) {
+  InlinedVector<const char*, 1> args_to_remove;
+  InlinedVector<grpc_arg, 2> args_to_add;
  // Add arg for targets info table.
-  grpc_core::RefCountedPtr<grpc_core::TargetAuthorityTable>
-      target_authority_table = grpc_core::CreateTargetAuthorityTable(addresses);
-  args_to_add[num_args_to_add++] =
-      grpc_core::CreateTargetAuthorityTableChannelArg(
-          target_authority_table.get());
+  RefCountedPtr<TargetAuthorityTable> target_authority_table =
+      CreateTargetAuthorityTable(addresses);
+  args_to_add.emplace_back(
+      CreateTargetAuthorityTableChannelArg(target_authority_table.get()));
  // Substitute the channel credentials with a version without call
  // credentials: the load balancer is not necessarily trusted to handle
  // bearer token credentials.
  grpc_channel_credentials* channel_credentials =
      grpc_channel_credentials_find_in_args(args);
-  grpc_core::RefCountedPtr<grpc_channel_credentials> creds_sans_call_creds;
+  RefCountedPtr<grpc_channel_credentials> creds_sans_call_creds;
  if (channel_credentials != nullptr) {
    creds_sans_call_creds =
        channel_credentials->duplicate_without_call_credentials();
    GPR_ASSERT(creds_sans_call_creds != nullptr);
-    args_to_remove[num_args_to_remove++] = GRPC_ARG_CHANNEL_CREDENTIALS;
-    args_to_add[num_args_to_add++] =
-        grpc_channel_credentials_to_arg(creds_sans_call_creds.get());
+    args_to_remove.emplace_back(GRPC_ARG_CHANNEL_CREDENTIALS);
+    args_to_add.emplace_back(
+        grpc_channel_credentials_to_arg(creds_sans_call_creds.get()));
  }
  grpc_channel_args* result = grpc_channel_args_copy_and_add_and_remove(
-      args, args_to_remove, num_args_to_remove, args_to_add, num_args_to_add);
+      args, args_to_remove.data(), args_to_remove.size(), args_to_add.data(),
+      args_to_add.size());
  // Clean up.
  grpc_channel_args_destroy(args);
  return result;
 }
+
+grpc_channel* CreateGrpclbBalancerChannel(const char* target_uri,
+                                          const grpc_channel_args& args) {
+  grpc_channel_credentials* creds =
+      grpc_channel_credentials_find_in_args(&args);
+  if (creds == nullptr) {
+    // Build with security but parent channel is insecure.
+    return grpc_insecure_channel_create(target_uri, &args, nullptr);
+  }
+  const char* arg_to_remove = GRPC_ARG_CHANNEL_CREDENTIALS;
+  grpc_channel_args* new_args =
+      grpc_channel_args_copy_and_remove(&args, &arg_to_remove, 1);
+  grpc_channel* channel =
+      grpc_secure_channel_create(creds, target_uri, new_args, nullptr);
+  grpc_channel_args_destroy(new_args);
+  return channel;
+}
+
+}  // namespace grpc_core
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc
@ -431,12 +431,10 @@ class XdsLb : public LoadBalancingPolicy {

    RefCountedPtr<SubchannelInterface> CreateSubchannel(
        const grpc_channel_args& args) override;
-    grpc_channel* CreateChannel(const char* target,
-                                const grpc_channel_args& args) override;
    void UpdateState(grpc_connectivity_state state,
                     UniquePtr<SubchannelPicker> picker) override;
    void RequestReresolution() override;
-    void AddTraceEvent(TraceSeverity severity, const char* message) override;
+    void AddTraceEvent(TraceSeverity severity, StringView message) override;

    void set_child(LoadBalancingPolicy* child) { child_ = child; }

@ -482,13 +480,10 @@ class XdsLb : public LoadBalancingPolicy {

        RefCountedPtr<SubchannelInterface> CreateSubchannel(
            const grpc_channel_args& args) override;
-        grpc_channel* CreateChannel(const char* target,
-                                    const grpc_channel_args& args) override;
        void UpdateState(grpc_connectivity_state state,
                         UniquePtr<SubchannelPicker> picker) override;
        void RequestReresolution() override;
-        void AddTraceEvent(TraceSeverity severity,
-                           const char* message) override;
+        void AddTraceEvent(TraceSeverity severity, StringView message) override;
        void set_child(LoadBalancingPolicy* child) { child_ = child; }

       private:
@ -723,15 +718,6 @@ RefCountedPtr<SubchannelInterface> XdsLb::FallbackHelper::CreateSubchannel(
  return parent_->channel_control_helper()->CreateSubchannel(args);
 }

-grpc_channel* XdsLb::FallbackHelper::CreateChannel(
-    const char* target, const grpc_channel_args& args) {
-  if (parent_->shutting_down_ ||
-      (!CalledByPendingFallback() && !CalledByCurrentFallback())) {
-    return nullptr;
-  }
-  return parent_->channel_control_helper()->CreateChannel(target, args);
-}
-
 void XdsLb::FallbackHelper::UpdateState(grpc_connectivity_state state,
                                        UniquePtr<SubchannelPicker> picker) {
  if (parent_->shutting_down_) return;
@ -774,7 +760,7 @@ void XdsLb::FallbackHelper::RequestReresolution() {
 }

 void XdsLb::FallbackHelper::AddTraceEvent(TraceSeverity severity,
-                                          const char* message) {
+                                          StringView message) {
  if (parent_->shutting_down_ ||
      (!CalledByPendingFallback() && !CalledByCurrentFallback())) {
    return;
@ -793,8 +779,7 @@ XdsLb::LbChannelState::LbChannelState(RefCountedPtr<XdsLb> xdslb_policy,
      xdslb_policy_(std::move(xdslb_policy)) {
  GRPC_CLOSURE_INIT(&on_connectivity_changed_, OnConnectivityChangedLocked,
                    this, grpc_combiner_scheduler(xdslb_policy_->combiner()));
-  channel_ = xdslb_policy_->channel_control_helper()->CreateChannel(
-      balancer_name, args);
+  channel_ = CreateXdsBalancerChannel(balancer_name, args);
  GPR_ASSERT(channel_ != nullptr);
  eds_calld_.reset(New<RetryableLbCall<EdsCallState>>(
      Ref(DEBUG_LOCATION, "LbChannelState+eds")));
@ -1672,7 +1657,7 @@ grpc_channel_args* BuildBalancerChannelArgs(const grpc_channel_args* args) {
      // factory will re-add this arg with the right value.
      GRPC_ARG_SERVER_URI,
      // The LB channel should use the authority indicated by the target
-      // authority table (see \a grpc_lb_policy_xds_modify_lb_channel_args),
+      // authority table (see \a ModifyXdsBalancerChannelArgs),
      // as opposed to the authority from the parent channel.
      GRPC_ARG_DEFAULT_AUTHORITY,
      // Just as for \a GRPC_ARG_DEFAULT_AUTHORITY, the LB channel should be
@ -1703,7 +1688,7 @@ grpc_channel_args* BuildBalancerChannelArgs(const grpc_channel_args* args) {
      args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), args_to_add.data(),
      args_to_add.size());
  // Make any necessary modifications for security.
-  return grpc_lb_policy_xds_modify_lb_channel_args(new_args);
+  return ModifyXdsBalancerChannelArgs(new_args);
 }

 //
@ -2440,15 +2425,6 @@ XdsLb::LocalityMap::LocalityEntry::Helper::CreateSubchannel(
  return entry_->parent_->channel_control_helper()->CreateSubchannel(args);
 }

-grpc_channel* XdsLb::LocalityMap::LocalityEntry::Helper::CreateChannel(
-    const char* target, const grpc_channel_args& args) {
-  if (entry_->parent_->shutting_down_ ||
-      (!CalledByPendingChild() && !CalledByCurrentChild())) {
-    return nullptr;
-  }
-  return entry_->parent_->channel_control_helper()->CreateChannel(target, args);
-}
-
 void XdsLb::LocalityMap::LocalityEntry::Helper::UpdateState(
    grpc_connectivity_state state, UniquePtr<SubchannelPicker> picker) {
  if (entry_->parent_->shutting_down_) return;
@ -2510,7 +2486,7 @@ void XdsLb::LocalityMap::LocalityEntry::Helper::RequestReresolution() {
 }

 void XdsLb::LocalityMap::LocalityEntry::Helper::AddTraceEvent(
-    TraceSeverity severity, const char* message) {
+    TraceSeverity severity, StringView message) {
  if (entry_->parent_->shutting_down_ ||
      (!CalledByPendingChild() && !CalledByCurrentChild())) {
    return;
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.cc
@ -18,9 +18,19 @@

 #include <grpc/support/port_platform.h>

+#include <grpc/grpc.h>
+
 #include "src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h"

-grpc_channel_args* grpc_lb_policy_xds_modify_lb_channel_args(
-    grpc_channel_args* args) {
+namespace grpc_core {
+
+grpc_channel_args* ModifyXdsBalancerChannelArgs(grpc_channel_args* args) {
  return args;
 }
+
+grpc_channel* CreateXdsBalancerChannel(const char* target_uri,
+                                       const grpc_channel_args& args) {
+  return grpc_insecure_channel_create(target_uri, &args, nullptr);
+}
+
+}  // namespace grpc_core
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h
@ -23,14 +23,20 @@

 #include <grpc/impl/codegen/grpc_types.h>

+namespace grpc_core {
+
 /// Makes any necessary modifications to \a args for use in the xds
 /// balancer channel.
 ///
 /// Takes ownership of \a args.
 ///
 /// Caller takes ownership of the returned args.
-grpc_channel_args* grpc_lb_policy_xds_modify_lb_channel_args(
-    grpc_channel_args* args);
+grpc_channel_args* ModifyXdsBalancerChannelArgs(grpc_channel_args* args);
+
+grpc_channel* CreateXdsBalancerChannel(const char* target_uri,
+                                       const grpc_channel_args& args);
+
+}  // namespace grpc_core

 #endif /* GRPC_CORE_EXT_FILTERS_CLIENT_CHANNEL_LB_POLICY_XDS_XDS_CHANNEL_H \
        */
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel_secure.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel_secure.cc
@ -20,9 +20,11 @@

 #include "src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h"

+#include <string.h>
+
+#include <grpc/grpc_security.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/string_util.h>
-#include <string.h>

 #include "src/core/ext/filters/client_channel/client_channel.h"
 #include "src/core/ext/filters/client_channel/server_address.h"
@ -33,29 +35,48 @@
 #include "src/core/lib/security/transport/target_authority_table.h"
 #include "src/core/lib/slice/slice_internal.h"

-grpc_channel_args* grpc_lb_policy_xds_modify_lb_channel_args(
-    grpc_channel_args* args) {
-  const char* args_to_remove[1];
-  size_t num_args_to_remove = 0;
-  grpc_arg args_to_add[2];
-  size_t num_args_to_add = 0;
+namespace grpc_core {
+
+grpc_channel_args* ModifyXdsBalancerChannelArgs(grpc_channel_args* args) {
+  InlinedVector<const char*, 1> args_to_remove;
+  InlinedVector<grpc_arg, 2> args_to_add;
  // Substitute the channel credentials with a version without call
  // credentials: the load balancer is not necessarily trusted to handle
  // bearer token credentials.
  grpc_channel_credentials* channel_credentials =
      grpc_channel_credentials_find_in_args(args);
-  grpc_core::RefCountedPtr<grpc_channel_credentials> creds_sans_call_creds;
+  RefCountedPtr<grpc_channel_credentials> creds_sans_call_creds;
  if (channel_credentials != nullptr) {
    creds_sans_call_creds =
        channel_credentials->duplicate_without_call_credentials();
    GPR_ASSERT(creds_sans_call_creds != nullptr);
-    args_to_remove[num_args_to_remove++] = GRPC_ARG_CHANNEL_CREDENTIALS;
-    args_to_add[num_args_to_add++] =
-        grpc_channel_credentials_to_arg(creds_sans_call_creds.get());
+    args_to_remove.emplace_back(GRPC_ARG_CHANNEL_CREDENTIALS);
+    args_to_add.emplace_back(
+        grpc_channel_credentials_to_arg(creds_sans_call_creds.get()));
  }
  grpc_channel_args* result = grpc_channel_args_copy_and_add_and_remove(
-      args, args_to_remove, num_args_to_remove, args_to_add, num_args_to_add);
+      args, args_to_remove.data(), args_to_remove.size(), args_to_add.data(),
+      args_to_add.size());
  // Clean up.
  grpc_channel_args_destroy(args);
  return result;
 }
+
+grpc_channel* CreateXdsBalancerChannel(const char* target_uri,
+                                       const grpc_channel_args& args) {
+  grpc_channel_credentials* creds =
+      grpc_channel_credentials_find_in_args(&args);
+  if (creds == nullptr) {
+    // Build with security but parent channel is insecure.
+    return grpc_insecure_channel_create(target_uri, &args, nullptr);
+  }
+  const char* arg_to_remove = GRPC_ARG_CHANNEL_CREDENTIALS;
+  grpc_channel_args* new_args =
+      grpc_channel_args_copy_and_remove(&args, &arg_to_remove, 1);
+  grpc_channel* channel =
+      grpc_secure_channel_create(creds, target_uri, new_args, nullptr);
+  grpc_channel_args_destroy(new_args);
+  return channel;
+}
+
+}  // namespace grpc_core
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_client_stats.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_client_stats.cc
@ -143,7 +143,15 @@ XdsClientStats::Snapshot XdsClientStats::GetSnapshotAndReset() {
  }
  {
    MutexLock lock(&dropped_requests_mu_);
+#if GRPC_USE_CPP_STD_LIB
+    // This is a workaround for the case where some compilers cannot build
+    // move-assignment of map with non-copyable but movable key.
+    // https://stackoverflow.com/questions/36475497
+    std::swap(snapshot.dropped_requests, dropped_requests_);
+    dropped_requests_.clear();
+#else
    snapshot.dropped_requests = std::move(dropped_requests_);
+#endif
  }
  return snapshot;
 }
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_load_balancer_api.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_load_balancer_api.cc
@ -315,7 +315,15 @@ grpc_slice XdsLrsRequestCreateAndEncode(const char* server_name) {
 namespace {

 void LocalityStatsPopulate(envoy_api_v2_endpoint_UpstreamLocalityStats* output,
+#if GRPC_USE_CPP_STD_LIB
+                           // TODO(veblush): Clean up this
+                           // This is to address the difference between
+                           // std::map and Map. #else block will be gone
+                           // once using stdlib is enabled by default.
+                           Pair<const RefCountedPtr<XdsLocalityName>,
+#else
                           Pair<RefCountedPtr<XdsLocalityName>,
+#endif
                                XdsClientStats::LocalityStats::Snapshot>& input,
                           upb_arena* arena) {
  // Set sub_zone.
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_load_balancer_api.h
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_load_balancer_api.h
@ -37,7 +37,8 @@ struct XdsLocalityInfo {

  // This comparator only compares the locality names.
  struct Less {
-    bool operator()(const XdsLocalityInfo& lhs, const XdsLocalityInfo& rhs) {
+    bool operator()(const XdsLocalityInfo& lhs,
+                    const XdsLocalityInfo& rhs) const {
      return XdsLocalityName::Less()(lhs.locality_name, rhs.locality_name);
    }
  };
--- a/src/core/ext/filters/client_channel/resolving_lb_policy.cc
+++ b/src/core/ext/filters/client_channel/resolving_lb_policy.cc
@ -113,13 +113,6 @@ class ResolvingLoadBalancingPolicy::ResolvingControlHelper
    return parent_->channel_control_helper()->CreateSubchannel(args);
  }

-  grpc_channel* CreateChannel(const char* target,
-                              const grpc_channel_args& args) override {
-    if (parent_->resolver_ == nullptr) return nullptr;  // Shutting down.
-    if (!CalledByCurrentChild() && !CalledByPendingChild()) return nullptr;
-    return parent_->channel_control_helper()->CreateChannel(target, args);
-  }
-
  void UpdateState(grpc_connectivity_state state,
                   UniquePtr<SubchannelPicker> picker) override {
    if (parent_->resolver_ == nullptr) return;  // Shutting down.
@ -160,6 +153,8 @@ class ResolvingLoadBalancingPolicy::ResolvingControlHelper
    }
  }

+  void AddTraceEvent(TraceSeverity severity, StringView message) override {}
+
  void set_child(LoadBalancingPolicy* child) { child_ = child; }

 private:
@ -433,7 +428,7 @@ void ResolvingLoadBalancingPolicy::ConcatenateAndAddChannelTraceLocked(
    size_t len = 0;
    UniquePtr<char> message(gpr_strvec_flatten(&v, &len));
    channel_control_helper()->AddTraceEvent(ChannelControlHelper::TRACE_INFO,
-                                            message.get());
+                                            StringView(message.get()));
    gpr_strvec_destroy(&v);
  }
 }
--- a/src/core/ext/filters/load_reporting/registered_opencensus_objects.h
+++ b/src/core/ext/filters/load_reporting/registered_opencensus_objects.h
@ -22,6 +22,7 @@
 #include <grpc/support/port_platform.h>

 #include "opencensus/stats/stats.h"
+#include "opencensus/tags/tag_key.h"

 #include "src/cpp/server/load_reporter/constants.h"

@ -80,33 +81,33 @@ inline ::opencensus::stats::MeasureDouble MeasureOtherCallMetric() {

 // Tags.

-inline ::opencensus::stats::TagKey TagKeyToken() {
-  static const ::opencensus::stats::TagKey token =
-      opencensus::stats::TagKey::Register(kTagKeyToken);
+inline ::opencensus::tags::TagKey TagKeyToken() {
+  static const ::opencensus::tags::TagKey token =
+      opencensus::tags::TagKey::Register(kTagKeyToken);
  return token;
 }

-inline ::opencensus::stats::TagKey TagKeyHost() {
-  static const ::opencensus::stats::TagKey token =
-      opencensus::stats::TagKey::Register(kTagKeyHost);
+inline ::opencensus::tags::TagKey TagKeyHost() {
+  static const ::opencensus::tags::TagKey token =
+      opencensus::tags::TagKey::Register(kTagKeyHost);
  return token;
 }

-inline ::opencensus::stats::TagKey TagKeyUserId() {
-  static const ::opencensus::stats::TagKey token =
-      opencensus::stats::TagKey::Register(kTagKeyUserId);
+inline ::opencensus::tags::TagKey TagKeyUserId() {
+  static const ::opencensus::tags::TagKey token =
+      opencensus::tags::TagKey::Register(kTagKeyUserId);
  return token;
 }

-inline ::opencensus::stats::TagKey TagKeyStatus() {
-  static const ::opencensus::stats::TagKey token =
-      opencensus::stats::TagKey::Register(kTagKeyStatus);
+inline ::opencensus::tags::TagKey TagKeyStatus() {
+  static const ::opencensus::tags::TagKey token =
+      opencensus::tags::TagKey::Register(kTagKeyStatus);
  return token;
 }

-inline ::opencensus::stats::TagKey TagKeyMetricName() {
-  static const ::opencensus::stats::TagKey token =
-      opencensus::stats::TagKey::Register(kTagKeyMetricName);
+inline ::opencensus::tags::TagKey TagKeyMetricName() {
+  static const ::opencensus::tags::TagKey token =
+      opencensus::tags::TagKey::Register(kTagKeyMetricName);
  return token;
 }

--- a/src/core/ext/transport/chttp2/client/insecure/channel_create.cc
+++ b/src/core/ext/transport/chttp2/client/insecure/channel_create.cc
@ -46,27 +46,30 @@ class Chttp2InsecureClientChannelFactory : public ClientChannelFactory {
    grpc_channel_args_destroy(new_args);
    return s;
  }
+};

-  grpc_channel* CreateChannel(const char* target,
-                              const grpc_channel_args* args) override {
-    if (target == nullptr) {
-      gpr_log(GPR_ERROR, "cannot create channel with NULL target name");
-      return nullptr;
-    }
-    // Add channel arg containing the server URI.
-    UniquePtr<char> canonical_target =
-        ResolverRegistry::AddDefaultPrefixIfNeeded(target);
-    grpc_arg arg = grpc_channel_arg_string_create(
-        const_cast<char*>(GRPC_ARG_SERVER_URI), canonical_target.get());
-    const char* to_remove[] = {GRPC_ARG_SERVER_URI};
-    grpc_channel_args* new_args =
-        grpc_channel_args_copy_and_add_and_remove(args, to_remove, 1, &arg, 1);
-    grpc_channel* channel =
-        grpc_channel_create(target, new_args, GRPC_CLIENT_CHANNEL, nullptr);
-    grpc_channel_args_destroy(new_args);
-    return channel;
+namespace {
+
+grpc_channel* CreateChannel(const char* target, const grpc_channel_args* args) {
+  if (target == nullptr) {
+    gpr_log(GPR_ERROR, "cannot create channel with NULL target name");
+    return nullptr;
  }
-};
+  // Add channel arg containing the server URI.
+  UniquePtr<char> canonical_target =
+      ResolverRegistry::AddDefaultPrefixIfNeeded(target);
+  grpc_arg arg = grpc_channel_arg_string_create(
+      const_cast<char*>(GRPC_ARG_SERVER_URI), canonical_target.get());
+  const char* to_remove[] = {GRPC_ARG_SERVER_URI};
+  grpc_channel_args* new_args =
+      grpc_channel_args_copy_and_add_and_remove(args, to_remove, 1, &arg, 1);
+  grpc_channel* channel =
+      grpc_channel_create(target, new_args, GRPC_CLIENT_CHANNEL, nullptr);
+  grpc_channel_args_destroy(new_args);
+  return channel;
+}
+
+}  // namespace

 }  // namespace grpc_core

@ -98,7 +101,7 @@ grpc_channel* grpc_insecure_channel_create(const char* target,
  grpc_arg arg = grpc_core::ClientChannelFactory::CreateChannelArg(g_factory);
  grpc_channel_args* new_args = grpc_channel_args_copy_and_add(args, &arg, 1);
  // Create channel.
-  grpc_channel* channel = g_factory->CreateChannel(target, new_args);
+  grpc_channel* channel = grpc_core::CreateChannel(target, new_args);
  // Clean up.
  grpc_channel_args_destroy(new_args);
  return channel != nullptr ? channel
--- a/src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc
+++ b/src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc
@ -58,26 +58,6 @@ class Chttp2SecureClientChannelFactory : public ClientChannelFactory {
    return s;
  }

-  grpc_channel* CreateChannel(const char* target,
-                              const grpc_channel_args* args) override {
-    if (target == nullptr) {
-      gpr_log(GPR_ERROR, "cannot create channel with NULL target name");
-      return nullptr;
-    }
-    // Add channel arg containing the server URI.
-    UniquePtr<char> canonical_target =
-        ResolverRegistry::AddDefaultPrefixIfNeeded(target);
-    grpc_arg arg = grpc_channel_arg_string_create(
-        const_cast<char*>(GRPC_ARG_SERVER_URI), canonical_target.get());
-    const char* to_remove[] = {GRPC_ARG_SERVER_URI};
-    grpc_channel_args* new_args =
-        grpc_channel_args_copy_and_add_and_remove(args, to_remove, 1, &arg, 1);
-    grpc_channel* channel =
-        grpc_channel_create(target, new_args, GRPC_CLIENT_CHANNEL, nullptr);
-    grpc_channel_args_destroy(new_args);
-    return channel;
-  }
-
 private:
  static grpc_channel_args* GetSecureNamingChannelArgs(
      const grpc_channel_args* args) {
@ -170,6 +150,29 @@ class Chttp2SecureClientChannelFactory : public ClientChannelFactory {
  }
 };

+namespace {
+
+grpc_channel* CreateChannel(const char* target, const grpc_channel_args* args) {
+  if (target == nullptr) {
+    gpr_log(GPR_ERROR, "cannot create channel with NULL target name");
+    return nullptr;
+  }
+  // Add channel arg containing the server URI.
+  UniquePtr<char> canonical_target =
+      ResolverRegistry::AddDefaultPrefixIfNeeded(target);
+  grpc_arg arg = grpc_channel_arg_string_create(
+      const_cast<char*>(GRPC_ARG_SERVER_URI), canonical_target.get());
+  const char* to_remove[] = {GRPC_ARG_SERVER_URI};
+  grpc_channel_args* new_args =
+      grpc_channel_args_copy_and_add_and_remove(args, to_remove, 1, &arg, 1);
+  grpc_channel* channel =
+      grpc_channel_create(target, new_args, GRPC_CLIENT_CHANNEL, nullptr);
+  grpc_channel_args_destroy(new_args);
+  return channel;
+}
+
+}  // namespace
+
 }  // namespace grpc_core

 namespace {
@ -209,7 +212,7 @@ grpc_channel* grpc_secure_channel_create(grpc_channel_credentials* creds,
        args, args_to_add, GPR_ARRAY_SIZE(args_to_add));
    new_args = creds->update_arguments(new_args);
    // Create channel.
-    channel = g_factory->CreateChannel(target, new_args);
+    channel = grpc_core::CreateChannel(target, new_args);
    // Clean up.
    grpc_channel_args_destroy(new_args);
  }
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
@ -2465,6 +2465,13 @@ static void cancel_stream_cb(void* user_data, uint32_t key, void* stream) {
 }

 static void end_all_the_calls(grpc_chttp2_transport* t, grpc_error* error) {
+  intptr_t http2_error;
+  // If there is no explicit grpc or HTTP/2 error, set to UNAVAILABLE on server.
+  if (!t->is_client && !grpc_error_has_clear_grpc_status(error) &&
+      !grpc_error_get_int(error, GRPC_ERROR_INT_HTTP2_ERROR, &http2_error)) {
+    error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS,
+                               GRPC_STATUS_UNAVAILABLE);
+  }
  cancel_stream_cb_args args = {error, t};
  grpc_chttp2_stream_map_for_each(&t->stream_map, cancel_stream_cb, &args);
  GRPC_ERROR_UNREF(error);
--- a/src/core/ext/transport/chttp2/transport/hpack_table.cc
+++ b/src/core/ext/transport/chttp2/transport/hpack_table.cc
@ -189,7 +189,7 @@ grpc_chttp2_hptbl_find_result grpc_chttp2_hptbl_find(

  /* See if the string is in the static table */
  for (i = 0; i < GRPC_CHTTP2_LAST_STATIC_ENTRY; i++) {
-    grpc_mdelem ent = grpc_static_mdelem_manifested[i];
+    grpc_mdelem ent = grpc_static_mdelem_manifested()[i];
    if (!grpc_slice_eq(GRPC_MDKEY(md), GRPC_MDKEY(ent))) continue;
    r.index = i + 1u;
    r.has_value = grpc_slice_eq(GRPC_MDVALUE(md), GRPC_MDVALUE(ent));
--- a/src/core/ext/transport/chttp2/transport/hpack_table.h
+++ b/src/core/ext/transport/chttp2/transport/hpack_table.h
@ -104,7 +104,7 @@ inline grpc_mdelem grpc_chttp2_hptbl_lookup(const grpc_chttp2_hptbl* tbl,
     reading the core static metadata table here; at that point we'd need our
     own singleton static metadata in the correct order. */
  return index <= GRPC_CHTTP2_LAST_STATIC_ENTRY
-             ? grpc_static_mdelem_manifested[index - 1]
+             ? grpc_static_mdelem_manifested()[index - 1]
             : grpc_chttp2_hptbl_lookup_dynamic_index(tbl, index);
 }
 /* add a table entry to the index */
@ -120,7 +120,7 @@ size_t grpc_chttp2_get_size_in_hpack_table(grpc_mdelem elem,
 inline uintptr_t grpc_chttp2_get_static_hpack_table_index(grpc_mdelem md) {
  uintptr_t index =
      reinterpret_cast<grpc_core::StaticMetadata*>(GRPC_MDELEM_DATA(md)) -
-      grpc_static_mdelem_table;
+      grpc_static_mdelem_table();
  if (index < GRPC_CHTTP2_LAST_STATIC_ENTRY) {
    return index + 1;  // Hpack static metadata element indices start at 1
  }
--- a/src/core/lib/channel/channelz.h
+++ b/src/core/lib/channel/channelz.h
@ -81,7 +81,10 @@ class BaseNode : public RefCounted<BaseNode> {
    kSocket,
  };

+ protected:
  BaseNode(EntityType type, UniquePtr<char> name);
+
+ public:
  virtual ~BaseNode();

  // All children must implement this function.
--- a/src/core/lib/gpr/log_linux.cc
+++ b/src/core/lib/gpr/log_linux.cc
@ -40,7 +40,7 @@
 #include <time.h>
 #include <unistd.h>

-static long gettid(void) { return syscall(__NR_gettid); }
+static long sys_gettid(void) { return syscall(__NR_gettid); }

 void gpr_log(const char* file, int line, gpr_log_severity severity,
             const char* format, ...) {
@ -70,7 +70,7 @@ void gpr_default_log(gpr_log_func_args* args) {
  gpr_timespec now = gpr_now(GPR_CLOCK_REALTIME);
  struct tm tm;
  static __thread long tid = 0;
-  if (tid == 0) tid = gettid();
+  if (tid == 0) tid = sys_gettid();

  timer = static_cast<time_t>(now.tv_sec);
  final_slash = strrchr(args->file, '/');
--- a/src/core/lib/gpr/log_posix.cc
+++ b/src/core/lib/gpr/log_posix.cc
@ -31,7 +31,7 @@
 #include <string.h>
 #include <time.h>

-static intptr_t gettid(void) { return (intptr_t)pthread_self(); }
+static intptr_t sys_gettid(void) { return (intptr_t)pthread_self(); }

 void gpr_log(const char* file, int line, gpr_log_severity severity,
             const char* format, ...) {
@ -86,7 +86,7 @@ void gpr_default_log(gpr_log_func_args* args) {
  char* prefix;
  gpr_asprintf(&prefix, "%s%s.%09d %7" PRIdPTR " %s:%d]",
               gpr_log_severity_string(args->severity), time_buffer,
-               (int)(now.tv_nsec), gettid(), display_file, args->line);
+               (int)(now.tv_nsec), sys_gettid(), display_file, args->line);

  fprintf(stderr, "%-70s %s\n", prefix, args->message);
  gpr_free(prefix);
--- a/src/core/lib/gprpp/abstract.h
+++ b/src/core/lib/gprpp/abstract.h
@ -19,6 +19,14 @@
 #ifndef GRPC_CORE_LIB_GPRPP_ABSTRACT_H
 #define GRPC_CORE_LIB_GPRPP_ABSTRACT_H

+#if GRPC_USE_CPP_STD_LIB
+
+#define GRPC_ABSTRACT_BASE_CLASS
+
+#define GRPC_ABSTRACT = 0
+
+#else
+
 // This is needed to support abstract base classes in the c core. Since gRPC
 // doesn't have a c++ runtime, it will hit a linker error on delete unless
 // we define a virtual operator delete. See this blog for more info:
@ -34,4 +42,6 @@
    GPR_ASSERT(false);                                                       \
  }

+#endif  // GRPC_USE_CPP_STD_LIB
+
 #endif /* GRPC_CORE_LIB_GPRPP_ABSTRACT_H */
--- a/src/core/lib/gprpp/map.h
+++ b/src/core/lib/gprpp/map.h
@ -27,12 +27,17 @@
 #include <functional>
 #include <iterator>

+#if GRPC_USE_CPP_STD_LIB
+#include <map>
+#endif
+
 #include "src/core/lib/gpr/useful.h"
 #include "src/core/lib/gprpp/memory.h"
 #include "src/core/lib/gprpp/pair.h"
 #include "src/core/lib/gprpp/ref_counted_ptr.h"

 namespace grpc_core {
+
 struct StringLess {
  bool operator()(const char* a, const char* b) const {
    return strcmp(a, b) < 0;
@ -50,6 +55,13 @@ struct RefCountedPtrLess {
  }
 };

+#if GRPC_USE_CPP_STD_LIB
+
+template <class Key, class T, class Compare = std::less<Key>>
+using Map = std::map<Key, T, Compare>;
+
+#else  // GRPC_USE_CPP_STD_LIB
+
 namespace testing {
 class MapTest;
 }
@ -63,6 +75,7 @@ class Map {
  typedef Pair<key_type, mapped_type> value_type;
  typedef Compare key_compare;
  class iterator;
+  class const_iterator;

  Map() = default;
  ~Map() { clear(); }
@ -83,6 +96,22 @@ class Map {
    return *this;
  }

+  // Copyable.
+  Map(const Map& other) {
+    for (const auto& p : other) {
+      emplace(p);
+    }
+  }
+  Map& operator=(const Map& other) {
+    if (this != &other) {
+      clear();
+      for (const auto& p : other) {
+        emplace(p);
+      }
+    }
+    return *this;
+  }
+
  T& operator[](key_type&& key);
  T& operator[](const key_type& key);
  iterator find(const key_type& k);
@ -117,6 +146,13 @@ class Map {

  iterator end() { return iterator(this, nullptr); }

+  const_iterator begin() const {
+    Entry* curr = GetMinEntry(root_);
+    return const_iterator(this, curr);
+  }
+
+  const_iterator end() const { return const_iterator(this, nullptr); }
+
  iterator lower_bound(const Key& k) {
    // This is a workaround for "const key_compare compare;"
    // because some versions of compilers cannot build this by requiring
@ -209,6 +245,53 @@ class Map<Key, T, Compare>::iterator
  GrpcMap* map_;
 };

+template <class Key, class T, class Compare>
+class Map<Key, T, Compare>::const_iterator
+    : public std::iterator<std::input_iterator_tag, Pair<Key, T>, int32_t,
+                           Pair<Key, T>*, Pair<Key, T>&> {
+ public:
+  const_iterator(const const_iterator& iter)
+      : curr_(iter.curr_), map_(iter.map_) {}
+  bool operator==(const const_iterator& rhs) const {
+    return (curr_ == rhs.curr_);
+  }
+  bool operator!=(const const_iterator& rhs) const {
+    return (curr_ != rhs.curr_);
+  }
+
+  const_iterator& operator++() {
+    curr_ = map_->InOrderSuccessor(curr_);
+    return *this;
+  }
+
+  const_iterator operator++(int) {
+    Entry* prev = curr_;
+    curr_ = map_->InOrderSuccessor(curr_);
+    return const_iterator(map_, prev);
+  }
+
+  const_iterator& operator=(const const_iterator& other) {
+    if (this != &other) {
+      this->curr_ = other.curr_;
+      this->map_ = other.map_;
+    }
+    return *this;
+  }
+
+  // operator*()
+  const value_type& operator*() const { return curr_->pair; }
+
+  // operator->()
+  const value_type* operator->() const { return &curr_->pair; }
+
+ private:
+  friend class Map<key_type, mapped_type, key_compare>;
+  using GrpcMap = typename ::grpc_core::Map<Key, T, Compare>;
+  const_iterator(const GrpcMap* map, Entry* curr) : curr_(curr), map_(map) {}
+  Entry* curr_;
+  const GrpcMap* map_;
+};
+
 template <class Key, class T, class Compare>
 T& Map<Key, T, Compare>::operator[](key_type&& key) {
  auto iter = find(key);
@ -466,5 +549,9 @@ int Map<Key, T, Compare>::CompareKeys(const key_type& lhs,
  }
  return left_comparison ? -1 : 1;
 }
+
+#endif  // GRPC_USE_CPP_STD_LIB
+
 }  // namespace grpc_core
+
 #endif /* GRPC_CORE_LIB_GPRPP_MAP_H */
--- a/src/core/lib/iomgr/ev_epollex_linux.cc
+++ b/src/core/lib/iomgr/ev_epollex_linux.cc
@ -1077,7 +1077,7 @@ static void end_worker(grpc_pollset* pollset, grpc_pollset_worker* worker,
 }

 #ifndef NDEBUG
-static long gettid(void) { return syscall(__NR_gettid); }
+static long sys_gettid(void) { return syscall(__NR_gettid); }
 #endif

 /* pollset->mu lock must be held by the caller before calling this.
@ -1097,7 +1097,7 @@ static grpc_error* pollset_work(grpc_pollset* pollset,
 #define WORKER_PTR (&worker)
 #endif
 #ifndef NDEBUG
-  WORKER_PTR->originator = gettid();
+  WORKER_PTR->originator = sys_gettid();
 #endif
  if (GRPC_TRACE_FLAG_ENABLED(grpc_polling_trace)) {
    gpr_log(GPR_INFO,
--- a/src/core/lib/iomgr/tcp_server_custom.cc
+++ b/src/core/lib/iomgr/tcp_server_custom.cc
@ -392,7 +392,7 @@ static grpc_error* tcp_server_add_port(grpc_tcp_server* s,
  socket->endpoint = nullptr;
  socket->listener = nullptr;
  socket->connector = nullptr;
-  grpc_custom_socket_vtable->init(socket, family);
+  error = grpc_custom_socket_vtable->init(socket, family);

  if (error == GRPC_ERROR_NONE) {
    error = add_socket_to_server(s, socket, addr, port_index, &sp);
--- a/src/core/lib/security/credentials/credentials.h
+++ b/src/core/lib/security/credentials/credentials.h
@ -110,11 +110,17 @@ struct grpc_channel_credentials
  create_security_connector(
      grpc_core::RefCountedPtr<grpc_call_credentials> call_creds,
      const char* target, const grpc_channel_args* args,
-      grpc_channel_args** new_args) {
+      grpc_channel_args** new_args)
+#if GRPC_USE_CPP_STD_LIB
+      = 0;
+#else
+  {
    // Tell clang-tidy that call_creds cannot be passed as const-ref.
    call_creds.reset();
-    GRPC_ABSTRACT;
+    gpr_log(GPR_ERROR, "Function marked GRPC_ABSTRACT was not implemented");
+    GPR_ASSERT(false);
  }
+#endif

  // Creates a version of the channel credentials without any attached call
  // credentials. This can be used in order to open a channel to a non-trusted
--- a/src/core/lib/slice/slice_intern.cc
+++ b/src/core/lib/slice/slice_intern.cc
@ -138,11 +138,12 @@ grpc_slice grpc_slice_maybe_static_intern(grpc_slice slice,
  for (uint32_t i = 0; i <= max_static_metadata_hash_probe; i++) {
    static_metadata_hash_ent ent =
        static_metadata_hash[(hash + i) % GPR_ARRAY_SIZE(static_metadata_hash)];
+    const grpc_core::StaticMetadataSlice* static_slice_table =
+        grpc_static_slice_table();
    if (ent.hash == hash && ent.idx < GRPC_STATIC_MDSTR_COUNT &&
-        grpc_slice_eq_static_interned(slice,
-                                      grpc_static_slice_table[ent.idx])) {
+        grpc_slice_eq_static_interned(slice, static_slice_table[ent.idx])) {
      *returned_slice_is_different = true;
-      return grpc_static_slice_table[ent.idx];
+      return static_slice_table[ent.idx];
    }
  }

@ -168,10 +169,11 @@ static const grpc_core::StaticMetadataSlice* MatchStaticSlice(
  for (uint32_t i = 0; i <= max_static_metadata_hash_probe; i++) {
    static_metadata_hash_ent ent =
        static_metadata_hash[(hash + i) % GPR_ARRAY_SIZE(static_metadata_hash)];
+    const grpc_core::StaticMetadataSlice* static_slice_table =
+        grpc_static_slice_table();
    if (ent.hash == hash && ent.idx < GRPC_STATIC_MDSTR_COUNT &&
-        grpc_static_slice_table[ent.idx].Equals(
-            std::forward<SliceArgs>(args)...)) {
-      return &grpc_static_slice_table[ent.idx];
+        static_slice_table[ent.idx].Equals(std::forward<SliceArgs>(args)...)) {
+      return &static_slice_table[ent.idx];
    }
  }
  return nullptr;
@ -318,9 +320,11 @@ void grpc_slice_intern_init(void) {
    static_metadata_hash[i].idx = GRPC_STATIC_MDSTR_COUNT;
  }
  max_static_metadata_hash_probe = 0;
+  const grpc_core::StaticMetadataSlice* static_slice_table =
+      grpc_static_slice_table();
  for (size_t i = 0; i < GRPC_STATIC_MDSTR_COUNT; i++) {
    grpc_static_metadata_hash_values[i] =
-        grpc_slice_default_hash_internal(grpc_static_slice_table[i]);
+        grpc_slice_default_hash_internal(static_slice_table[i]);
    for (size_t j = 0; j < GPR_ARRAY_SIZE(static_metadata_hash); j++) {
      size_t slot = (grpc_static_metadata_hash_values[i] + j) %
                    GPR_ARRAY_SIZE(static_metadata_hash);
@ -336,7 +340,7 @@ void grpc_slice_intern_init(void) {
  }
  // Handle KV hash for all static mdelems.
  for (size_t i = 0; i < GRPC_STATIC_MDELEM_COUNT; ++i) {
-    grpc_static_mdelem_table[i].HashInit();
+    grpc_static_mdelem_table()[i].HashInit();
  }
 }

--- a/src/core/lib/slice/slice_internal.h
+++ b/src/core/lib/slice/slice_internal.h
@ -182,7 +182,7 @@ struct StaticSliceRefcount {
        index(index) {}

  grpc_slice_refcount base;
-  uint32_t index;
+  const uint32_t index;
 };

 extern grpc_slice_refcount kNoopRefcount;
--- a/src/core/lib/slice/slice_utils.h
+++ b/src/core/lib/slice/slice_utils.h
@ -108,7 +108,7 @@ struct ManagedMemorySlice : public grpc_slice {
    return !grpc_slice_differs_refcounted(other, *this);
  }
  bool Equals(const char* buf, const size_t len) const {
-    return data.refcounted.length == len &&
+    return data.refcounted.length == len && buf != nullptr &&
           memcmp(buf, data.refcounted.bytes, len) == 0;
  }
 };
@ -153,10 +153,14 @@ struct ExternallyManagedSlice : public UnmanagedMemorySlice {
 };

 struct StaticMetadataSlice : public ManagedMemorySlice {
-  StaticMetadataSlice(grpc_slice_refcount* ref, size_t length, uint8_t* bytes) {
+  StaticMetadataSlice(grpc_slice_refcount* ref, size_t length,
+                      const uint8_t* bytes) {
    refcount = ref;
    data.refcounted.length = length;
-    data.refcounted.bytes = bytes;
+    // NB: grpc_slice may or may not point to a static slice, but we are
+    // definitely pointing to static data here. Since we are not changing
+    // the underlying C-type, we need a const_cast here.
+    data.refcounted.bytes = const_cast<uint8_t*>(bytes);
  }
 };

--- a/src/core/lib/surface/init.cc
+++ b/src/core/lib/surface/init.cc
@ -134,6 +134,7 @@ void grpc_init(void) {
    grpc_core::Fork::GlobalInit();
    grpc_fork_handlers_auto_register();
    grpc_stats_init();
+    grpc_init_static_metadata_ctx();
    grpc_slice_intern_init();
    grpc_mdctx_global_init();
    grpc_channel_init_init();
@ -191,6 +192,8 @@ void grpc_shutdown_internal_locked(void) {
  grpc_core::ApplicationCallbackExecCtx::GlobalShutdown();
  g_shutting_down = false;
  gpr_cv_broadcast(g_shutting_down_cv);
+  // Absolute last action will be to delete static metadata context.
+  grpc_destroy_static_metadata_ctx();
 }

 void grpc_shutdown_internal(void* ignored) {
--- a/src/core/lib/transport/metadata.cc
+++ b/src/core/lib/transport/metadata.cc
@ -269,9 +269,9 @@ void grpc_mdctx_global_shutdown() {
 #ifndef NDEBUG
 static int is_mdelem_static(grpc_mdelem e) {
  return reinterpret_cast<grpc_core::StaticMetadata*>(GRPC_MDELEM_DATA(e)) >=
-             &grpc_static_mdelem_table[0] &&
+             &grpc_static_mdelem_table()[0] &&
         reinterpret_cast<grpc_core::StaticMetadata*>(GRPC_MDELEM_DATA(e)) <
-             &grpc_static_mdelem_table[GRPC_STATIC_MDELEM_COUNT];
+             &grpc_static_mdelem_table()[GRPC_STATIC_MDELEM_COUNT];
 }
 #endif

@ -569,7 +569,7 @@ void* grpc_mdelem_get_user_data(grpc_mdelem md, void (*destroy_func)(void*)) {
          grpc_static_mdelem_user_data
              [reinterpret_cast<grpc_core::StaticMetadata*>(
                   GRPC_MDELEM_DATA(md)) -
-               grpc_static_mdelem_table]);
+               grpc_static_mdelem_table()]);
    case GRPC_MDELEM_STORAGE_ALLOCATED: {
      auto* am = reinterpret_cast<AllocatedMetadata*>(GRPC_MDELEM_DATA(md));
      return get_user_data(am->user_data(), destroy_func);
@ -611,7 +611,7 @@ void* grpc_mdelem_set_user_data(grpc_mdelem md, void (*destroy_func)(void*),
          grpc_static_mdelem_user_data
              [reinterpret_cast<grpc_core::StaticMetadata*>(
                   GRPC_MDELEM_DATA(md)) -
-               grpc_static_mdelem_table]);
+               grpc_static_mdelem_table()]);
    case GRPC_MDELEM_STORAGE_ALLOCATED: {
      auto* am = reinterpret_cast<AllocatedMetadata*>(GRPC_MDELEM_DATA(md));
      return set_user_data(am->user_data(), destroy_func, data);
--- a/src/core/lib/transport/static_metadata.cc
+++ b/src/core/lib/transport/static_metadata.cc
--- a/src/core/lib/transport/static_metadata.h
+++ b/src/core/lib/transport/static_metadata.h
@ -37,240 +37,262 @@ static_assert(
    std::is_trivially_destructible<grpc_core::StaticMetadataSlice>::value,
    "grpc_core::StaticMetadataSlice must be trivially destructible.");
 #define GRPC_STATIC_MDSTR_COUNT 108
-extern const grpc_core::StaticMetadataSlice
-    grpc_static_slice_table[GRPC_STATIC_MDSTR_COUNT];
+
+void grpc_init_static_metadata_ctx(void);
+void grpc_destroy_static_metadata_ctx(void);
+namespace grpc_core {
+#ifndef NDEBUG
+constexpr uint64_t kGrpcStaticMetadataInitCanary = 0xCAFEF00DC0FFEE11L;
+uint64_t StaticMetadataInitCanary();
+#endif
+extern const StaticMetadataSlice* g_static_metadata_slice_table;
+}
+inline const grpc_core::StaticMetadataSlice* grpc_static_slice_table() {
+  GPR_DEBUG_ASSERT(grpc_core::StaticMetadataInitCanary() ==
+                   grpc_core::kGrpcStaticMetadataInitCanary);
+  GPR_DEBUG_ASSERT(grpc_core::g_static_metadata_slice_table != nullptr);
+  return grpc_core::g_static_metadata_slice_table;
+}
+
 /* ":path" */
-#define GRPC_MDSTR_PATH (grpc_static_slice_table[0])
+#define GRPC_MDSTR_PATH (grpc_static_slice_table()[0])
 /* ":method" */
-#define GRPC_MDSTR_METHOD (grpc_static_slice_table[1])
+#define GRPC_MDSTR_METHOD (grpc_static_slice_table()[1])
 /* ":status" */
-#define GRPC_MDSTR_STATUS (grpc_static_slice_table[2])
+#define GRPC_MDSTR_STATUS (grpc_static_slice_table()[2])
 /* ":authority" */
-#define GRPC_MDSTR_AUTHORITY (grpc_static_slice_table[3])
+#define GRPC_MDSTR_AUTHORITY (grpc_static_slice_table()[3])
 /* ":scheme" */
-#define GRPC_MDSTR_SCHEME (grpc_static_slice_table[4])
+#define GRPC_MDSTR_SCHEME (grpc_static_slice_table()[4])
 /* "te" */
-#define GRPC_MDSTR_TE (grpc_static_slice_table[5])
+#define GRPC_MDSTR_TE (grpc_static_slice_table()[5])
 /* "grpc-message" */
-#define GRPC_MDSTR_GRPC_MESSAGE (grpc_static_slice_table[6])
+#define GRPC_MDSTR_GRPC_MESSAGE (grpc_static_slice_table()[6])
 /* "grpc-status" */
-#define GRPC_MDSTR_GRPC_STATUS (grpc_static_slice_table[7])
+#define GRPC_MDSTR_GRPC_STATUS (grpc_static_slice_table()[7])
 /* "grpc-payload-bin" */
-#define GRPC_MDSTR_GRPC_PAYLOAD_BIN (grpc_static_slice_table[8])
+#define GRPC_MDSTR_GRPC_PAYLOAD_BIN (grpc_static_slice_table()[8])
 /* "grpc-encoding" */
-#define GRPC_MDSTR_GRPC_ENCODING (grpc_static_slice_table[9])
+#define GRPC_MDSTR_GRPC_ENCODING (grpc_static_slice_table()[9])
 /* "grpc-accept-encoding" */
-#define GRPC_MDSTR_GRPC_ACCEPT_ENCODING (grpc_static_slice_table[10])
+#define GRPC_MDSTR_GRPC_ACCEPT_ENCODING (grpc_static_slice_table()[10])
 /* "grpc-server-stats-bin" */
-#define GRPC_MDSTR_GRPC_SERVER_STATS_BIN (grpc_static_slice_table[11])
+#define GRPC_MDSTR_GRPC_SERVER_STATS_BIN (grpc_static_slice_table()[11])
 /* "grpc-tags-bin" */
-#define GRPC_MDSTR_GRPC_TAGS_BIN (grpc_static_slice_table[12])
+#define GRPC_MDSTR_GRPC_TAGS_BIN (grpc_static_slice_table()[12])
 /* "grpc-trace-bin" */
-#define GRPC_MDSTR_GRPC_TRACE_BIN (grpc_static_slice_table[13])
+#define GRPC_MDSTR_GRPC_TRACE_BIN (grpc_static_slice_table()[13])
 /* "content-type" */
-#define GRPC_MDSTR_CONTENT_TYPE (grpc_static_slice_table[14])
+#define GRPC_MDSTR_CONTENT_TYPE (grpc_static_slice_table()[14])
 /* "content-encoding" */
-#define GRPC_MDSTR_CONTENT_ENCODING (grpc_static_slice_table[15])
+#define GRPC_MDSTR_CONTENT_ENCODING (grpc_static_slice_table()[15])
 /* "accept-encoding" */
-#define GRPC_MDSTR_ACCEPT_ENCODING (grpc_static_slice_table[16])
+#define GRPC_MDSTR_ACCEPT_ENCODING (grpc_static_slice_table()[16])
 /* "grpc-internal-encoding-request" */
-#define GRPC_MDSTR_GRPC_INTERNAL_ENCODING_REQUEST (grpc_static_slice_table[17])
+#define GRPC_MDSTR_GRPC_INTERNAL_ENCODING_REQUEST \
+  (grpc_static_slice_table()[17])
 /* "grpc-internal-stream-encoding-request" */
 #define GRPC_MDSTR_GRPC_INTERNAL_STREAM_ENCODING_REQUEST \
-  (grpc_static_slice_table[18])
+  (grpc_static_slice_table()[18])
 /* "user-agent" */
-#define GRPC_MDSTR_USER_AGENT (grpc_static_slice_table[19])
+#define GRPC_MDSTR_USER_AGENT (grpc_static_slice_table()[19])
 /* "host" */
-#define GRPC_MDSTR_HOST (grpc_static_slice_table[20])
+#define GRPC_MDSTR_HOST (grpc_static_slice_table()[20])
 /* "grpc-previous-rpc-attempts" */
-#define GRPC_MDSTR_GRPC_PREVIOUS_RPC_ATTEMPTS (grpc_static_slice_table[21])
+#define GRPC_MDSTR_GRPC_PREVIOUS_RPC_ATTEMPTS (grpc_static_slice_table()[21])
 /* "grpc-retry-pushback-ms" */
-#define GRPC_MDSTR_GRPC_RETRY_PUSHBACK_MS (grpc_static_slice_table[22])
+#define GRPC_MDSTR_GRPC_RETRY_PUSHBACK_MS (grpc_static_slice_table()[22])
 /* "grpc-timeout" */
-#define GRPC_MDSTR_GRPC_TIMEOUT (grpc_static_slice_table[23])
+#define GRPC_MDSTR_GRPC_TIMEOUT (grpc_static_slice_table()[23])
 /* "1" */
-#define GRPC_MDSTR_1 (grpc_static_slice_table[24])
+#define GRPC_MDSTR_1 (grpc_static_slice_table()[24])
 /* "2" */
-#define GRPC_MDSTR_2 (grpc_static_slice_table[25])
+#define GRPC_MDSTR_2 (grpc_static_slice_table()[25])
 /* "3" */
-#define GRPC_MDSTR_3 (grpc_static_slice_table[26])
+#define GRPC_MDSTR_3 (grpc_static_slice_table()[26])
 /* "4" */
-#define GRPC_MDSTR_4 (grpc_static_slice_table[27])
+#define GRPC_MDSTR_4 (grpc_static_slice_table()[27])
 /* "" */
-#define GRPC_MDSTR_EMPTY (grpc_static_slice_table[28])
+#define GRPC_MDSTR_EMPTY (grpc_static_slice_table()[28])
 /* "grpc.wait_for_ready" */
-#define GRPC_MDSTR_GRPC_DOT_WAIT_FOR_READY (grpc_static_slice_table[29])
+#define GRPC_MDSTR_GRPC_DOT_WAIT_FOR_READY (grpc_static_slice_table()[29])
 /* "grpc.timeout" */
-#define GRPC_MDSTR_GRPC_DOT_TIMEOUT (grpc_static_slice_table[30])
+#define GRPC_MDSTR_GRPC_DOT_TIMEOUT (grpc_static_slice_table()[30])
 /* "grpc.max_request_message_bytes" */
 #define GRPC_MDSTR_GRPC_DOT_MAX_REQUEST_MESSAGE_BYTES \
-  (grpc_static_slice_table[31])
+  (grpc_static_slice_table()[31])
 /* "grpc.max_response_message_bytes" */
 #define GRPC_MDSTR_GRPC_DOT_MAX_RESPONSE_MESSAGE_BYTES \
-  (grpc_static_slice_table[32])
+  (grpc_static_slice_table()[32])
 /* "/grpc.lb.v1.LoadBalancer/BalanceLoad" */
 #define GRPC_MDSTR_SLASH_GRPC_DOT_LB_DOT_V1_DOT_LOADBALANCER_SLASH_BALANCELOAD \
-  (grpc_static_slice_table[33])
+  (grpc_static_slice_table()[33])
 /* "/envoy.service.load_stats.v2.LoadReportingService/StreamLoadStats" */
 #define GRPC_MDSTR_SLASH_ENVOY_DOT_SERVICE_DOT_LOAD_STATS_DOT_V2_DOT_LOADREPORTINGSERVICE_SLASH_STREAMLOADSTATS \
-  (grpc_static_slice_table[34])
+  (grpc_static_slice_table()[34])
 /* "/envoy.api.v2.EndpointDiscoveryService/StreamEndpoints" */
 #define GRPC_MDSTR_SLASH_ENVOY_DOT_API_DOT_V2_DOT_ENDPOINTDISCOVERYSERVICE_SLASH_STREAMENDPOINTS \
-  (grpc_static_slice_table[35])
+  (grpc_static_slice_table()[35])
 /* "/grpc.health.v1.Health/Watch" */
 #define GRPC_MDSTR_SLASH_GRPC_DOT_HEALTH_DOT_V1_DOT_HEALTH_SLASH_WATCH \
-  (grpc_static_slice_table[36])
+  (grpc_static_slice_table()[36])
 /* "/envoy.service.discovery.v2.AggregatedDiscoveryService/StreamAggregatedResources"
 */
 #define GRPC_MDSTR_SLASH_ENVOY_DOT_SERVICE_DOT_DISCOVERY_DOT_V2_DOT_AGGREGATEDDISCOVERYSERVICE_SLASH_STREAMAGGREGATEDRESOURCES \
-  (grpc_static_slice_table[37])
+  (grpc_static_slice_table()[37])
 /* "deflate" */
-#define GRPC_MDSTR_DEFLATE (grpc_static_slice_table[38])
+#define GRPC_MDSTR_DEFLATE (grpc_static_slice_table()[38])
 /* "gzip" */
-#define GRPC_MDSTR_GZIP (grpc_static_slice_table[39])
+#define GRPC_MDSTR_GZIP (grpc_static_slice_table()[39])
 /* "stream/gzip" */
-#define GRPC_MDSTR_STREAM_SLASH_GZIP (grpc_static_slice_table[40])
+#define GRPC_MDSTR_STREAM_SLASH_GZIP (grpc_static_slice_table()[40])
 /* "GET" */
-#define GRPC_MDSTR_GET (grpc_static_slice_table[41])
+#define GRPC_MDSTR_GET (grpc_static_slice_table()[41])
 /* "POST" */
-#define GRPC_MDSTR_POST (grpc_static_slice_table[42])
+#define GRPC_MDSTR_POST (grpc_static_slice_table()[42])
 /* "/" */
-#define GRPC_MDSTR_SLASH (grpc_static_slice_table[43])
+#define GRPC_MDSTR_SLASH (grpc_static_slice_table()[43])
 /* "/index.html" */
-#define GRPC_MDSTR_SLASH_INDEX_DOT_HTML (grpc_static_slice_table[44])
+#define GRPC_MDSTR_SLASH_INDEX_DOT_HTML (grpc_static_slice_table()[44])
 /* "http" */
-#define GRPC_MDSTR_HTTP (grpc_static_slice_table[45])
+#define GRPC_MDSTR_HTTP (grpc_static_slice_table()[45])
 /* "https" */
-#define GRPC_MDSTR_HTTPS (grpc_static_slice_table[46])
+#define GRPC_MDSTR_HTTPS (grpc_static_slice_table()[46])
 /* "200" */
-#define GRPC_MDSTR_200 (grpc_static_slice_table[47])
+#define GRPC_MDSTR_200 (grpc_static_slice_table()[47])
 /* "204" */
-#define GRPC_MDSTR_204 (grpc_static_slice_table[48])
+#define GRPC_MDSTR_204 (grpc_static_slice_table()[48])
 /* "206" */
-#define GRPC_MDSTR_206 (grpc_static_slice_table[49])
+#define GRPC_MDSTR_206 (grpc_static_slice_table()[49])
 /* "304" */
-#define GRPC_MDSTR_304 (grpc_static_slice_table[50])
+#define GRPC_MDSTR_304 (grpc_static_slice_table()[50])
 /* "400" */
-#define GRPC_MDSTR_400 (grpc_static_slice_table[51])
+#define GRPC_MDSTR_400 (grpc_static_slice_table()[51])
 /* "404" */
-#define GRPC_MDSTR_404 (grpc_static_slice_table[52])
+#define GRPC_MDSTR_404 (grpc_static_slice_table()[52])
 /* "500" */
-#define GRPC_MDSTR_500 (grpc_static_slice_table[53])
+#define GRPC_MDSTR_500 (grpc_static_slice_table()[53])
 /* "accept-charset" */
-#define GRPC_MDSTR_ACCEPT_CHARSET (grpc_static_slice_table[54])
+#define GRPC_MDSTR_ACCEPT_CHARSET (grpc_static_slice_table()[54])
 /* "gzip, deflate" */
-#define GRPC_MDSTR_GZIP_COMMA_DEFLATE (grpc_static_slice_table[55])
+#define GRPC_MDSTR_GZIP_COMMA_DEFLATE (grpc_static_slice_table()[55])
 /* "accept-language" */
-#define GRPC_MDSTR_ACCEPT_LANGUAGE (grpc_static_slice_table[56])
+#define GRPC_MDSTR_ACCEPT_LANGUAGE (grpc_static_slice_table()[56])
 /* "accept-ranges" */
-#define GRPC_MDSTR_ACCEPT_RANGES (grpc_static_slice_table[57])
+#define GRPC_MDSTR_ACCEPT_RANGES (grpc_static_slice_table()[57])
 /* "accept" */
-#define GRPC_MDSTR_ACCEPT (grpc_static_slice_table[58])
+#define GRPC_MDSTR_ACCEPT (grpc_static_slice_table()[58])
 /* "access-control-allow-origin" */
-#define GRPC_MDSTR_ACCESS_CONTROL_ALLOW_ORIGIN (grpc_static_slice_table[59])
+#define GRPC_MDSTR_ACCESS_CONTROL_ALLOW_ORIGIN (grpc_static_slice_table()[59])
 /* "age" */
-#define GRPC_MDSTR_AGE (grpc_static_slice_table[60])
+#define GRPC_MDSTR_AGE (grpc_static_slice_table()[60])
 /* "allow" */
-#define GRPC_MDSTR_ALLOW (grpc_static_slice_table[61])
+#define GRPC_MDSTR_ALLOW (grpc_static_slice_table()[61])
 /* "authorization" */
-#define GRPC_MDSTR_AUTHORIZATION (grpc_static_slice_table[62])
+#define GRPC_MDSTR_AUTHORIZATION (grpc_static_slice_table()[62])
 /* "cache-control" */
-#define GRPC_MDSTR_CACHE_CONTROL (grpc_static_slice_table[63])
+#define GRPC_MDSTR_CACHE_CONTROL (grpc_static_slice_table()[63])
 /* "content-disposition" */
-#define GRPC_MDSTR_CONTENT_DISPOSITION (grpc_static_slice_table[64])
+#define GRPC_MDSTR_CONTENT_DISPOSITION (grpc_static_slice_table()[64])
 /* "content-language" */
-#define GRPC_MDSTR_CONTENT_LANGUAGE (grpc_static_slice_table[65])
+#define GRPC_MDSTR_CONTENT_LANGUAGE (grpc_static_slice_table()[65])
 /* "content-length" */
-#define GRPC_MDSTR_CONTENT_LENGTH (grpc_static_slice_table[66])
+#define GRPC_MDSTR_CONTENT_LENGTH (grpc_static_slice_table()[66])
 /* "content-location" */
-#define GRPC_MDSTR_CONTENT_LOCATION (grpc_static_slice_table[67])
+#define GRPC_MDSTR_CONTENT_LOCATION (grpc_static_slice_table()[67])
 /* "content-range" */
-#define GRPC_MDSTR_CONTENT_RANGE (grpc_static_slice_table[68])
+#define GRPC_MDSTR_CONTENT_RANGE (grpc_static_slice_table()[68])
 /* "cookie" */
-#define GRPC_MDSTR_COOKIE (grpc_static_slice_table[69])
+#define GRPC_MDSTR_COOKIE (grpc_static_slice_table()[69])
 /* "date" */
-#define GRPC_MDSTR_DATE (grpc_static_slice_table[70])
+#define GRPC_MDSTR_DATE (grpc_static_slice_table()[70])
 /* "etag" */
-#define GRPC_MDSTR_ETAG (grpc_static_slice_table[71])
+#define GRPC_MDSTR_ETAG (grpc_static_slice_table()[71])
 /* "expect" */
-#define GRPC_MDSTR_EXPECT (grpc_static_slice_table[72])
+#define GRPC_MDSTR_EXPECT (grpc_static_slice_table()[72])
 /* "expires" */
-#define GRPC_MDSTR_EXPIRES (grpc_static_slice_table[73])
+#define GRPC_MDSTR_EXPIRES (grpc_static_slice_table()[73])
 /* "from" */
-#define GRPC_MDSTR_FROM (grpc_static_slice_table[74])
+#define GRPC_MDSTR_FROM (grpc_static_slice_table()[74])
 /* "if-match" */
-#define GRPC_MDSTR_IF_MATCH (grpc_static_slice_table[75])
+#define GRPC_MDSTR_IF_MATCH (grpc_static_slice_table()[75])
 /* "if-modified-since" */
-#define GRPC_MDSTR_IF_MODIFIED_SINCE (grpc_static_slice_table[76])
+#define GRPC_MDSTR_IF_MODIFIED_SINCE (grpc_static_slice_table()[76])
 /* "if-none-match" */
-#define GRPC_MDSTR_IF_NONE_MATCH (grpc_static_slice_table[77])
+#define GRPC_MDSTR_IF_NONE_MATCH (grpc_static_slice_table()[77])
 /* "if-range" */
-#define GRPC_MDSTR_IF_RANGE (grpc_static_slice_table[78])
+#define GRPC_MDSTR_IF_RANGE (grpc_static_slice_table()[78])
 /* "if-unmodified-since" */
-#define GRPC_MDSTR_IF_UNMODIFIED_SINCE (grpc_static_slice_table[79])
+#define GRPC_MDSTR_IF_UNMODIFIED_SINCE (grpc_static_slice_table()[79])
 /* "last-modified" */
-#define GRPC_MDSTR_LAST_MODIFIED (grpc_static_slice_table[80])
+#define GRPC_MDSTR_LAST_MODIFIED (grpc_static_slice_table()[80])
 /* "link" */
-#define GRPC_MDSTR_LINK (grpc_static_slice_table[81])
+#define GRPC_MDSTR_LINK (grpc_static_slice_table()[81])
 /* "location" */
-#define GRPC_MDSTR_LOCATION (grpc_static_slice_table[82])
+#define GRPC_MDSTR_LOCATION (grpc_static_slice_table()[82])
 /* "max-forwards" */
-#define GRPC_MDSTR_MAX_FORWARDS (grpc_static_slice_table[83])
+#define GRPC_MDSTR_MAX_FORWARDS (grpc_static_slice_table()[83])
 /* "proxy-authenticate" */
-#define GRPC_MDSTR_PROXY_AUTHENTICATE (grpc_static_slice_table[84])
+#define GRPC_MDSTR_PROXY_AUTHENTICATE (grpc_static_slice_table()[84])
 /* "proxy-authorization" */
-#define GRPC_MDSTR_PROXY_AUTHORIZATION (grpc_static_slice_table[85])
+#define GRPC_MDSTR_PROXY_AUTHORIZATION (grpc_static_slice_table()[85])
 /* "range" */
-#define GRPC_MDSTR_RANGE (grpc_static_slice_table[86])
+#define GRPC_MDSTR_RANGE (grpc_static_slice_table()[86])
 /* "referer" */
-#define GRPC_MDSTR_REFERER (grpc_static_slice_table[87])
+#define GRPC_MDSTR_REFERER (grpc_static_slice_table()[87])
 /* "refresh" */
-#define GRPC_MDSTR_REFRESH (grpc_static_slice_table[88])
+#define GRPC_MDSTR_REFRESH (grpc_static_slice_table()[88])
 /* "retry-after" */
-#define GRPC_MDSTR_RETRY_AFTER (grpc_static_slice_table[89])
+#define GRPC_MDSTR_RETRY_AFTER (grpc_static_slice_table()[89])
 /* "server" */
-#define GRPC_MDSTR_SERVER (grpc_static_slice_table[90])
+#define GRPC_MDSTR_SERVER (grpc_static_slice_table()[90])
 /* "set-cookie" */
-#define GRPC_MDSTR_SET_COOKIE (grpc_static_slice_table[91])
+#define GRPC_MDSTR_SET_COOKIE (grpc_static_slice_table()[91])
 /* "strict-transport-security" */
-#define GRPC_MDSTR_STRICT_TRANSPORT_SECURITY (grpc_static_slice_table[92])
+#define GRPC_MDSTR_STRICT_TRANSPORT_SECURITY (grpc_static_slice_table()[92])
 /* "transfer-encoding" */
-#define GRPC_MDSTR_TRANSFER_ENCODING (grpc_static_slice_table[93])
+#define GRPC_MDSTR_TRANSFER_ENCODING (grpc_static_slice_table()[93])
 /* "vary" */
-#define GRPC_MDSTR_VARY (grpc_static_slice_table[94])
+#define GRPC_MDSTR_VARY (grpc_static_slice_table()[94])
 /* "via" */
-#define GRPC_MDSTR_VIA (grpc_static_slice_table[95])
+#define GRPC_MDSTR_VIA (grpc_static_slice_table()[95])
 /* "www-authenticate" */
-#define GRPC_MDSTR_WWW_AUTHENTICATE (grpc_static_slice_table[96])
+#define GRPC_MDSTR_WWW_AUTHENTICATE (grpc_static_slice_table()[96])
 /* "0" */
-#define GRPC_MDSTR_0 (grpc_static_slice_table[97])
+#define GRPC_MDSTR_0 (grpc_static_slice_table()[97])
 /* "identity" */
-#define GRPC_MDSTR_IDENTITY (grpc_static_slice_table[98])
+#define GRPC_MDSTR_IDENTITY (grpc_static_slice_table()[98])
 /* "trailers" */
-#define GRPC_MDSTR_TRAILERS (grpc_static_slice_table[99])
+#define GRPC_MDSTR_TRAILERS (grpc_static_slice_table()[99])
 /* "application/grpc" */
-#define GRPC_MDSTR_APPLICATION_SLASH_GRPC (grpc_static_slice_table[100])
+#define GRPC_MDSTR_APPLICATION_SLASH_GRPC (grpc_static_slice_table()[100])
 /* "grpc" */
-#define GRPC_MDSTR_GRPC (grpc_static_slice_table[101])
+#define GRPC_MDSTR_GRPC (grpc_static_slice_table()[101])
 /* "PUT" */
-#define GRPC_MDSTR_PUT (grpc_static_slice_table[102])
+#define GRPC_MDSTR_PUT (grpc_static_slice_table()[102])
 /* "lb-cost-bin" */
-#define GRPC_MDSTR_LB_COST_BIN (grpc_static_slice_table[103])
+#define GRPC_MDSTR_LB_COST_BIN (grpc_static_slice_table()[103])
 /* "identity,deflate" */
-#define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE (grpc_static_slice_table[104])
+#define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE (grpc_static_slice_table()[104])
 /* "identity,gzip" */
-#define GRPC_MDSTR_IDENTITY_COMMA_GZIP (grpc_static_slice_table[105])
+#define GRPC_MDSTR_IDENTITY_COMMA_GZIP (grpc_static_slice_table()[105])
 /* "deflate,gzip" */
-#define GRPC_MDSTR_DEFLATE_COMMA_GZIP (grpc_static_slice_table[106])
+#define GRPC_MDSTR_DEFLATE_COMMA_GZIP (grpc_static_slice_table()[106])
 /* "identity,deflate,gzip" */
 #define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE_COMMA_GZIP \
-  (grpc_static_slice_table[107])
+  (grpc_static_slice_table()[107])

 namespace grpc_core {
 struct StaticSliceRefcount;
+extern StaticSliceRefcount* g_static_metadata_slice_refcounts;
+}  // namespace grpc_core
+inline grpc_core::StaticSliceRefcount* grpc_static_metadata_refcounts() {
+  GPR_DEBUG_ASSERT(grpc_core::StaticMetadataInitCanary() ==
+                   grpc_core::kGrpcStaticMetadataInitCanary);
+  GPR_DEBUG_ASSERT(grpc_core::g_static_metadata_slice_refcounts != nullptr);
+  return grpc_core::g_static_metadata_slice_refcounts;
 }
-extern grpc_core::StaticSliceRefcount
-    grpc_static_metadata_refcounts[GRPC_STATIC_MDSTR_COUNT];
+
 #define GRPC_IS_STATIC_METADATA_STRING(slice) \
  ((slice).refcount != NULL &&                \
   (slice).refcount->GetType() == grpc_slice_refcount::Type::STATIC)
@ -280,196 +302,216 @@ extern grpc_core::StaticSliceRefcount
       ->index)

 #define GRPC_STATIC_MDELEM_COUNT 85
-extern grpc_core::StaticMetadata
-    grpc_static_mdelem_table[GRPC_STATIC_MDELEM_COUNT];
+
+namespace grpc_core {
+extern StaticMetadata* g_static_mdelem_table;
+extern grpc_mdelem* g_static_mdelem_manifested;
+}  // namespace grpc_core
+inline grpc_core::StaticMetadata* grpc_static_mdelem_table() {
+  GPR_DEBUG_ASSERT(grpc_core::StaticMetadataInitCanary() ==
+                   grpc_core::kGrpcStaticMetadataInitCanary);
+  GPR_DEBUG_ASSERT(grpc_core::g_static_mdelem_table != nullptr);
+  return grpc_core::g_static_mdelem_table;
+}
+inline grpc_mdelem* grpc_static_mdelem_manifested() {
+  GPR_DEBUG_ASSERT(grpc_core::StaticMetadataInitCanary() ==
+                   grpc_core::kGrpcStaticMetadataInitCanary);
+  GPR_DEBUG_ASSERT(grpc_core::g_static_mdelem_manifested != nullptr);
+  return grpc_core::g_static_mdelem_manifested;
+}
+
 extern uintptr_t grpc_static_mdelem_user_data[GRPC_STATIC_MDELEM_COUNT];
-extern grpc_mdelem grpc_static_mdelem_manifested[GRPC_STATIC_MDELEM_COUNT];
 /* ":authority": "" */
-#define GRPC_MDELEM_AUTHORITY_EMPTY (grpc_static_mdelem_manifested[0])
+#define GRPC_MDELEM_AUTHORITY_EMPTY (grpc_static_mdelem_manifested()[0])
 /* ":method": "GET" */
-#define GRPC_MDELEM_METHOD_GET (grpc_static_mdelem_manifested[1])
+#define GRPC_MDELEM_METHOD_GET (grpc_static_mdelem_manifested()[1])
 /* ":method": "POST" */
-#define GRPC_MDELEM_METHOD_POST (grpc_static_mdelem_manifested[2])
+#define GRPC_MDELEM_METHOD_POST (grpc_static_mdelem_manifested()[2])
 /* ":path": "/" */
-#define GRPC_MDELEM_PATH_SLASH (grpc_static_mdelem_manifested[3])
+#define GRPC_MDELEM_PATH_SLASH (grpc_static_mdelem_manifested()[3])
 /* ":path": "/index.html" */
-#define GRPC_MDELEM_PATH_SLASH_INDEX_DOT_HTML (grpc_static_mdelem_manifested[4])
+#define GRPC_MDELEM_PATH_SLASH_INDEX_DOT_HTML \
+  (grpc_static_mdelem_manifested()[4])
 /* ":scheme": "http" */
-#define GRPC_MDELEM_SCHEME_HTTP (grpc_static_mdelem_manifested[5])
+#define GRPC_MDELEM_SCHEME_HTTP (grpc_static_mdelem_manifested()[5])
 /* ":scheme": "https" */
-#define GRPC_MDELEM_SCHEME_HTTPS (grpc_static_mdelem_manifested[6])
+#define GRPC_MDELEM_SCHEME_HTTPS (grpc_static_mdelem_manifested()[6])
 /* ":status": "200" */
-#define GRPC_MDELEM_STATUS_200 (grpc_static_mdelem_manifested[7])
+#define GRPC_MDELEM_STATUS_200 (grpc_static_mdelem_manifested()[7])
 /* ":status": "204" */
-#define GRPC_MDELEM_STATUS_204 (grpc_static_mdelem_manifested[8])
+#define GRPC_MDELEM_STATUS_204 (grpc_static_mdelem_manifested()[8])
 /* ":status": "206" */
-#define GRPC_MDELEM_STATUS_206 (grpc_static_mdelem_manifested[9])
+#define GRPC_MDELEM_STATUS_206 (grpc_static_mdelem_manifested()[9])
 /* ":status": "304" */
-#define GRPC_MDELEM_STATUS_304 (grpc_static_mdelem_manifested[10])
+#define GRPC_MDELEM_STATUS_304 (grpc_static_mdelem_manifested()[10])
 /* ":status": "400" */
-#define GRPC_MDELEM_STATUS_400 (grpc_static_mdelem_manifested[11])
+#define GRPC_MDELEM_STATUS_400 (grpc_static_mdelem_manifested()[11])
 /* ":status": "404" */
-#define GRPC_MDELEM_STATUS_404 (grpc_static_mdelem_manifested[12])
+#define GRPC_MDELEM_STATUS_404 (grpc_static_mdelem_manifested()[12])
 /* ":status": "500" */
-#define GRPC_MDELEM_STATUS_500 (grpc_static_mdelem_manifested[13])
+#define GRPC_MDELEM_STATUS_500 (grpc_static_mdelem_manifested()[13])
 /* "accept-charset": "" */
-#define GRPC_MDELEM_ACCEPT_CHARSET_EMPTY (grpc_static_mdelem_manifested[14])
+#define GRPC_MDELEM_ACCEPT_CHARSET_EMPTY (grpc_static_mdelem_manifested()[14])
 /* "accept-encoding": "gzip, deflate" */
 #define GRPC_MDELEM_ACCEPT_ENCODING_GZIP_COMMA_DEFLATE \
-  (grpc_static_mdelem_manifested[15])
+  (grpc_static_mdelem_manifested()[15])
 /* "accept-language": "" */
-#define GRPC_MDELEM_ACCEPT_LANGUAGE_EMPTY (grpc_static_mdelem_manifested[16])
+#define GRPC_MDELEM_ACCEPT_LANGUAGE_EMPTY (grpc_static_mdelem_manifested()[16])
 /* "accept-ranges": "" */
-#define GRPC_MDELEM_ACCEPT_RANGES_EMPTY (grpc_static_mdelem_manifested[17])
+#define GRPC_MDELEM_ACCEPT_RANGES_EMPTY (grpc_static_mdelem_manifested()[17])
 /* "accept": "" */
-#define GRPC_MDELEM_ACCEPT_EMPTY (grpc_static_mdelem_manifested[18])
+#define GRPC_MDELEM_ACCEPT_EMPTY (grpc_static_mdelem_manifested()[18])
 /* "access-control-allow-origin": "" */
 #define GRPC_MDELEM_ACCESS_CONTROL_ALLOW_ORIGIN_EMPTY \
-  (grpc_static_mdelem_manifested[19])
+  (grpc_static_mdelem_manifested()[19])
 /* "age": "" */
-#define GRPC_MDELEM_AGE_EMPTY (grpc_static_mdelem_manifested[20])
+#define GRPC_MDELEM_AGE_EMPTY (grpc_static_mdelem_manifested()[20])
 /* "allow": "" */
-#define GRPC_MDELEM_ALLOW_EMPTY (grpc_static_mdelem_manifested[21])
+#define GRPC_MDELEM_ALLOW_EMPTY (grpc_static_mdelem_manifested()[21])
 /* "authorization": "" */
-#define GRPC_MDELEM_AUTHORIZATION_EMPTY (grpc_static_mdelem_manifested[22])
+#define GRPC_MDELEM_AUTHORIZATION_EMPTY (grpc_static_mdelem_manifested()[22])
 /* "cache-control": "" */
-#define GRPC_MDELEM_CACHE_CONTROL_EMPTY (grpc_static_mdelem_manifested[23])
+#define GRPC_MDELEM_CACHE_CONTROL_EMPTY (grpc_static_mdelem_manifested()[23])
 /* "content-disposition": "" */
 #define GRPC_MDELEM_CONTENT_DISPOSITION_EMPTY \
-  (grpc_static_mdelem_manifested[24])
+  (grpc_static_mdelem_manifested()[24])
 /* "content-encoding": "" */
-#define GRPC_MDELEM_CONTENT_ENCODING_EMPTY (grpc_static_mdelem_manifested[25])
+#define GRPC_MDELEM_CONTENT_ENCODING_EMPTY (grpc_static_mdelem_manifested()[25])
 /* "content-language": "" */
-#define GRPC_MDELEM_CONTENT_LANGUAGE_EMPTY (grpc_static_mdelem_manifested[26])
+#define GRPC_MDELEM_CONTENT_LANGUAGE_EMPTY (grpc_static_mdelem_manifested()[26])
 /* "content-length": "" */
-#define GRPC_MDELEM_CONTENT_LENGTH_EMPTY (grpc_static_mdelem_manifested[27])
+#define GRPC_MDELEM_CONTENT_LENGTH_EMPTY (grpc_static_mdelem_manifested()[27])
 /* "content-location": "" */
-#define GRPC_MDELEM_CONTENT_LOCATION_EMPTY (grpc_static_mdelem_manifested[28])
+#define GRPC_MDELEM_CONTENT_LOCATION_EMPTY (grpc_static_mdelem_manifested()[28])
 /* "content-range": "" */
-#define GRPC_MDELEM_CONTENT_RANGE_EMPTY (grpc_static_mdelem_manifested[29])
+#define GRPC_MDELEM_CONTENT_RANGE_EMPTY (grpc_static_mdelem_manifested()[29])
 /* "content-type": "" */
-#define GRPC_MDELEM_CONTENT_TYPE_EMPTY (grpc_static_mdelem_manifested[30])
+#define GRPC_MDELEM_CONTENT_TYPE_EMPTY (grpc_static_mdelem_manifested()[30])
 /* "cookie": "" */
-#define GRPC_MDELEM_COOKIE_EMPTY (grpc_static_mdelem_manifested[31])
+#define GRPC_MDELEM_COOKIE_EMPTY (grpc_static_mdelem_manifested()[31])
 /* "date": "" */
-#define GRPC_MDELEM_DATE_EMPTY (grpc_static_mdelem_manifested[32])
+#define GRPC_MDELEM_DATE_EMPTY (grpc_static_mdelem_manifested()[32])
 /* "etag": "" */
-#define GRPC_MDELEM_ETAG_EMPTY (grpc_static_mdelem_manifested[33])
+#define GRPC_MDELEM_ETAG_EMPTY (grpc_static_mdelem_manifested()[33])
 /* "expect": "" */
-#define GRPC_MDELEM_EXPECT_EMPTY (grpc_static_mdelem_manifested[34])
+#define GRPC_MDELEM_EXPECT_EMPTY (grpc_static_mdelem_manifested()[34])
 /* "expires": "" */
-#define GRPC_MDELEM_EXPIRES_EMPTY (grpc_static_mdelem_manifested[35])
+#define GRPC_MDELEM_EXPIRES_EMPTY (grpc_static_mdelem_manifested()[35])
 /* "from": "" */
-#define GRPC_MDELEM_FROM_EMPTY (grpc_static_mdelem_manifested[36])
+#define GRPC_MDELEM_FROM_EMPTY (grpc_static_mdelem_manifested()[36])
 /* "host": "" */
-#define GRPC_MDELEM_HOST_EMPTY (grpc_static_mdelem_manifested[37])
+#define GRPC_MDELEM_HOST_EMPTY (grpc_static_mdelem_manifested()[37])
 /* "if-match": "" */
-#define GRPC_MDELEM_IF_MATCH_EMPTY (grpc_static_mdelem_manifested[38])
+#define GRPC_MDELEM_IF_MATCH_EMPTY (grpc_static_mdelem_manifested()[38])
 /* "if-modified-since": "" */
-#define GRPC_MDELEM_IF_MODIFIED_SINCE_EMPTY (grpc_static_mdelem_manifested[39])
+#define GRPC_MDELEM_IF_MODIFIED_SINCE_EMPTY \
+  (grpc_static_mdelem_manifested()[39])
 /* "if-none-match": "" */
-#define GRPC_MDELEM_IF_NONE_MATCH_EMPTY (grpc_static_mdelem_manifested[40])
+#define GRPC_MDELEM_IF_NONE_MATCH_EMPTY (grpc_static_mdelem_manifested()[40])
 /* "if-range": "" */
-#define GRPC_MDELEM_IF_RANGE_EMPTY (grpc_static_mdelem_manifested[41])
+#define GRPC_MDELEM_IF_RANGE_EMPTY (grpc_static_mdelem_manifested()[41])
 /* "if-unmodified-since": "" */
 #define GRPC_MDELEM_IF_UNMODIFIED_SINCE_EMPTY \
-  (grpc_static_mdelem_manifested[42])
+  (grpc_static_mdelem_manifested()[42])
 /* "last-modified": "" */
-#define GRPC_MDELEM_LAST_MODIFIED_EMPTY (grpc_static_mdelem_manifested[43])
+#define GRPC_MDELEM_LAST_MODIFIED_EMPTY (grpc_static_mdelem_manifested()[43])
 /* "link": "" */
-#define GRPC_MDELEM_LINK_EMPTY (grpc_static_mdelem_manifested[44])
+#define GRPC_MDELEM_LINK_EMPTY (grpc_static_mdelem_manifested()[44])
 /* "location": "" */
-#define GRPC_MDELEM_LOCATION_EMPTY (grpc_static_mdelem_manifested[45])
+#define GRPC_MDELEM_LOCATION_EMPTY (grpc_static_mdelem_manifested()[45])
 /* "max-forwards": "" */
-#define GRPC_MDELEM_MAX_FORWARDS_EMPTY (grpc_static_mdelem_manifested[46])
+#define GRPC_MDELEM_MAX_FORWARDS_EMPTY (grpc_static_mdelem_manifested()[46])
 /* "proxy-authenticate": "" */
-#define GRPC_MDELEM_PROXY_AUTHENTICATE_EMPTY (grpc_static_mdelem_manifested[47])
+#define GRPC_MDELEM_PROXY_AUTHENTICATE_EMPTY \
+  (grpc_static_mdelem_manifested()[47])
 /* "proxy-authorization": "" */
 #define GRPC_MDELEM_PROXY_AUTHORIZATION_EMPTY \
-  (grpc_static_mdelem_manifested[48])
+  (grpc_static_mdelem_manifested()[48])
 /* "range": "" */
-#define GRPC_MDELEM_RANGE_EMPTY (grpc_static_mdelem_manifested[49])
+#define GRPC_MDELEM_RANGE_EMPTY (grpc_static_mdelem_manifested()[49])
 /* "referer": "" */
-#define GRPC_MDELEM_REFERER_EMPTY (grpc_static_mdelem_manifested[50])
+#define GRPC_MDELEM_REFERER_EMPTY (grpc_static_mdelem_manifested()[50])
 /* "refresh": "" */
-#define GRPC_MDELEM_REFRESH_EMPTY (grpc_static_mdelem_manifested[51])
+#define GRPC_MDELEM_REFRESH_EMPTY (grpc_static_mdelem_manifested()[51])
 /* "retry-after": "" */
-#define GRPC_MDELEM_RETRY_AFTER_EMPTY (grpc_static_mdelem_manifested[52])
+#define GRPC_MDELEM_RETRY_AFTER_EMPTY (grpc_static_mdelem_manifested()[52])
 /* "server": "" */
-#define GRPC_MDELEM_SERVER_EMPTY (grpc_static_mdelem_manifested[53])
+#define GRPC_MDELEM_SERVER_EMPTY (grpc_static_mdelem_manifested()[53])
 /* "set-cookie": "" */
-#define GRPC_MDELEM_SET_COOKIE_EMPTY (grpc_static_mdelem_manifested[54])
+#define GRPC_MDELEM_SET_COOKIE_EMPTY (grpc_static_mdelem_manifested()[54])
 /* "strict-transport-security": "" */
 #define GRPC_MDELEM_STRICT_TRANSPORT_SECURITY_EMPTY \
-  (grpc_static_mdelem_manifested[55])
+  (grpc_static_mdelem_manifested()[55])
 /* "transfer-encoding": "" */
-#define GRPC_MDELEM_TRANSFER_ENCODING_EMPTY (grpc_static_mdelem_manifested[56])
+#define GRPC_MDELEM_TRANSFER_ENCODING_EMPTY \
+  (grpc_static_mdelem_manifested()[56])
 /* "user-agent": "" */
-#define GRPC_MDELEM_USER_AGENT_EMPTY (grpc_static_mdelem_manifested[57])
+#define GRPC_MDELEM_USER_AGENT_EMPTY (grpc_static_mdelem_manifested()[57])
 /* "vary": "" */
-#define GRPC_MDELEM_VARY_EMPTY (grpc_static_mdelem_manifested[58])
+#define GRPC_MDELEM_VARY_EMPTY (grpc_static_mdelem_manifested()[58])
 /* "via": "" */
-#define GRPC_MDELEM_VIA_EMPTY (grpc_static_mdelem_manifested[59])
+#define GRPC_MDELEM_VIA_EMPTY (grpc_static_mdelem_manifested()[59])
 /* "www-authenticate": "" */
-#define GRPC_MDELEM_WWW_AUTHENTICATE_EMPTY (grpc_static_mdelem_manifested[60])
+#define GRPC_MDELEM_WWW_AUTHENTICATE_EMPTY (grpc_static_mdelem_manifested()[60])
 /* "grpc-status": "0" */
-#define GRPC_MDELEM_GRPC_STATUS_0 (grpc_static_mdelem_manifested[61])
+#define GRPC_MDELEM_GRPC_STATUS_0 (grpc_static_mdelem_manifested()[61])
 /* "grpc-status": "1" */
-#define GRPC_MDELEM_GRPC_STATUS_1 (grpc_static_mdelem_manifested[62])
+#define GRPC_MDELEM_GRPC_STATUS_1 (grpc_static_mdelem_manifested()[62])
 /* "grpc-status": "2" */
-#define GRPC_MDELEM_GRPC_STATUS_2 (grpc_static_mdelem_manifested[63])
+#define GRPC_MDELEM_GRPC_STATUS_2 (grpc_static_mdelem_manifested()[63])
 /* "grpc-encoding": "identity" */
-#define GRPC_MDELEM_GRPC_ENCODING_IDENTITY (grpc_static_mdelem_manifested[64])
+#define GRPC_MDELEM_GRPC_ENCODING_IDENTITY (grpc_static_mdelem_manifested()[64])
 /* "grpc-encoding": "gzip" */
-#define GRPC_MDELEM_GRPC_ENCODING_GZIP (grpc_static_mdelem_manifested[65])
+#define GRPC_MDELEM_GRPC_ENCODING_GZIP (grpc_static_mdelem_manifested()[65])
 /* "grpc-encoding": "deflate" */
-#define GRPC_MDELEM_GRPC_ENCODING_DEFLATE (grpc_static_mdelem_manifested[66])
+#define GRPC_MDELEM_GRPC_ENCODING_DEFLATE (grpc_static_mdelem_manifested()[66])
 /* "te": "trailers" */
-#define GRPC_MDELEM_TE_TRAILERS (grpc_static_mdelem_manifested[67])
+#define GRPC_MDELEM_TE_TRAILERS (grpc_static_mdelem_manifested()[67])
 /* "content-type": "application/grpc" */
 #define GRPC_MDELEM_CONTENT_TYPE_APPLICATION_SLASH_GRPC \
-  (grpc_static_mdelem_manifested[68])
+  (grpc_static_mdelem_manifested()[68])
 /* ":scheme": "grpc" */
-#define GRPC_MDELEM_SCHEME_GRPC (grpc_static_mdelem_manifested[69])
+#define GRPC_MDELEM_SCHEME_GRPC (grpc_static_mdelem_manifested()[69])
 /* ":method": "PUT" */
-#define GRPC_MDELEM_METHOD_PUT (grpc_static_mdelem_manifested[70])
+#define GRPC_MDELEM_METHOD_PUT (grpc_static_mdelem_manifested()[70])
 /* "accept-encoding": "" */
-#define GRPC_MDELEM_ACCEPT_ENCODING_EMPTY (grpc_static_mdelem_manifested[71])
+#define GRPC_MDELEM_ACCEPT_ENCODING_EMPTY (grpc_static_mdelem_manifested()[71])
 /* "content-encoding": "identity" */
 #define GRPC_MDELEM_CONTENT_ENCODING_IDENTITY \
-  (grpc_static_mdelem_manifested[72])
+  (grpc_static_mdelem_manifested()[72])
 /* "content-encoding": "gzip" */
-#define GRPC_MDELEM_CONTENT_ENCODING_GZIP (grpc_static_mdelem_manifested[73])
+#define GRPC_MDELEM_CONTENT_ENCODING_GZIP (grpc_static_mdelem_manifested()[73])
 /* "lb-cost-bin": "" */
-#define GRPC_MDELEM_LB_COST_BIN_EMPTY (grpc_static_mdelem_manifested[74])
+#define GRPC_MDELEM_LB_COST_BIN_EMPTY (grpc_static_mdelem_manifested()[74])
 /* "grpc-accept-encoding": "identity" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_IDENTITY \
-  (grpc_static_mdelem_manifested[75])
+  (grpc_static_mdelem_manifested()[75])
 /* "grpc-accept-encoding": "deflate" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_DEFLATE \
-  (grpc_static_mdelem_manifested[76])
+  (grpc_static_mdelem_manifested()[76])
 /* "grpc-accept-encoding": "identity,deflate" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_IDENTITY_COMMA_DEFLATE \
-  (grpc_static_mdelem_manifested[77])
+  (grpc_static_mdelem_manifested()[77])
 /* "grpc-accept-encoding": "gzip" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_GZIP \
-  (grpc_static_mdelem_manifested[78])
+  (grpc_static_mdelem_manifested()[78])
 /* "grpc-accept-encoding": "identity,gzip" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_IDENTITY_COMMA_GZIP \
-  (grpc_static_mdelem_manifested[79])
+  (grpc_static_mdelem_manifested()[79])
 /* "grpc-accept-encoding": "deflate,gzip" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_DEFLATE_COMMA_GZIP \
-  (grpc_static_mdelem_manifested[80])
+  (grpc_static_mdelem_manifested()[80])
 /* "grpc-accept-encoding": "identity,deflate,gzip" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_IDENTITY_COMMA_DEFLATE_COMMA_GZIP \
-  (grpc_static_mdelem_manifested[81])
+  (grpc_static_mdelem_manifested()[81])
 /* "accept-encoding": "identity" */
-#define GRPC_MDELEM_ACCEPT_ENCODING_IDENTITY (grpc_static_mdelem_manifested[82])
+#define GRPC_MDELEM_ACCEPT_ENCODING_IDENTITY \
+  (grpc_static_mdelem_manifested()[82])
 /* "accept-encoding": "gzip" */
-#define GRPC_MDELEM_ACCEPT_ENCODING_GZIP (grpc_static_mdelem_manifested[83])
+#define GRPC_MDELEM_ACCEPT_ENCODING_GZIP (grpc_static_mdelem_manifested()[83])
 /* "accept-encoding": "identity,gzip" */
 #define GRPC_MDELEM_ACCEPT_ENCODING_IDENTITY_COMMA_GZIP \
-  (grpc_static_mdelem_manifested[84])
+  (grpc_static_mdelem_manifested()[84])

 grpc_mdelem grpc_static_mdelem_for_static_strings(intptr_t a, intptr_t b);
 typedef enum {
@ -539,15 +581,15 @@ typedef union {
       : GRPC_BATCH_CALLOUTS_COUNT)

 extern const uint8_t grpc_static_accept_encoding_metadata[8];
-#define GRPC_MDELEM_ACCEPT_ENCODING_FOR_ALGORITHMS(algs)                      \
-  (GRPC_MAKE_MDELEM(                                                          \
-      &grpc_static_mdelem_table[grpc_static_accept_encoding_metadata[(algs)]] \
-           .data(),                                                           \
-      GRPC_MDELEM_STORAGE_STATIC))
+#define GRPC_MDELEM_ACCEPT_ENCODING_FOR_ALGORITHMS(algs)                \
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table()                         \
+                         [grpc_static_accept_encoding_metadata[(algs)]] \
+                             .data(),                                   \
+                    GRPC_MDELEM_STORAGE_STATIC))

 extern const uint8_t grpc_static_accept_stream_encoding_metadata[4];
 #define GRPC_MDELEM_ACCEPT_STREAM_ENCODING_FOR_ALGORITHMS(algs)                \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table                                  \
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table()                                \
                         [grpc_static_accept_stream_encoding_metadata[(algs)]] \
                             .data(),                                          \
                    GRPC_MDELEM_STORAGE_STATIC))
--- a/src/cpp/client/secure_credentials.cc
+++ b/src/cpp/client/secure_credentials.cc
@ -407,7 +407,7 @@ int MetadataCredentialsPluginWrapper::GetMetadata(
    *num_creds_md = 0;
    *status = GRPC_STATUS_OK;
    *error_details = nullptr;
-    return true;
+    return 1;
  }
  if (w->plugin_->IsBlocking()) {
    // The internals of context may be destroyed if GetMetadata is cancelled.
--- a/src/cpp/ext/filters/census/grpc_plugin.cc
+++ b/src/cpp/ext/filters/census/grpc_plugin.cc
@ -22,6 +22,7 @@

 #include <grpcpp/server_context.h>

+#include "opencensus/tags/tag_key.h"
 #include "opencensus/trace/span.h"
 #include "src/cpp/ext/filters/census/channel_filter.h"
 #include "src/cpp/ext/filters/census/client_filter.h"
@ -33,27 +34,27 @@ namespace grpc {
 // These measure definitions should be kept in sync across opencensus
 // implementations--see
 // https://github.com/census-instrumentation/opencensus-java/blob/master/contrib/grpc_metrics/src/main/java/io/opencensus/contrib/grpc/metrics/RpcMeasureConstants.java.
-::opencensus::stats::TagKey ClientMethodTagKey() {
+::opencensus::tags::TagKey ClientMethodTagKey() {
  static const auto method_tag_key =
-      ::opencensus::stats::TagKey::Register("grpc_client_method");
+      ::opencensus::tags::TagKey::Register("grpc_client_method");
  return method_tag_key;
 }

-::opencensus::stats::TagKey ClientStatusTagKey() {
+::opencensus::tags::TagKey ClientStatusTagKey() {
  static const auto status_tag_key =
-      ::opencensus::stats::TagKey::Register("grpc_client_status");
+      ::opencensus::tags::TagKey::Register("grpc_client_status");
  return status_tag_key;
 }

-::opencensus::stats::TagKey ServerMethodTagKey() {
+::opencensus::tags::TagKey ServerMethodTagKey() {
  static const auto method_tag_key =
-      ::opencensus::stats::TagKey::Register("grpc_server_method");
+      ::opencensus::tags::TagKey::Register("grpc_server_method");
  return method_tag_key;
 }

-::opencensus::stats::TagKey ServerStatusTagKey() {
+::opencensus::tags::TagKey ServerStatusTagKey() {
  static const auto status_tag_key =
-      ::opencensus::stats::TagKey::Register("grpc_server_status");
+      ::opencensus::tags::TagKey::Register("grpc_server_status");
  return status_tag_key;
 }

--- a/src/cpp/ext/filters/census/grpc_plugin.h
+++ b/src/cpp/ext/filters/census/grpc_plugin.h
@ -24,6 +24,7 @@
 #include "absl/strings/string_view.h"
 #include "include/grpcpp/opencensus.h"
 #include "opencensus/stats/stats.h"
+#include "opencensus/tags/tag_key.h"

 namespace grpc_impl {
 class ServerContext;
@ -32,10 +33,10 @@ class ServerContext;
 namespace grpc {

 // The tag keys set when recording RPC stats.
-::opencensus::stats::TagKey ClientMethodTagKey();
-::opencensus::stats::TagKey ClientStatusTagKey();
-::opencensus::stats::TagKey ServerMethodTagKey();
-::opencensus::stats::TagKey ServerStatusTagKey();
+::opencensus::tags::TagKey ClientMethodTagKey();
+::opencensus::tags::TagKey ClientStatusTagKey();
+::opencensus::tags::TagKey ServerMethodTagKey();
+::opencensus::tags::TagKey ServerStatusTagKey();

 // Names of measures used by the plugin--users can create views on these
 // measures but should not record data for them.
--- a/src/cpp/server/load_reporter/load_reporter.cc
+++ b/src/cpp/server/load_reporter/load_reporter.cc
@ -29,6 +29,7 @@
 #include "src/cpp/server/load_reporter/load_reporter.h"

 #include "opencensus/stats/internal/set_aggregation_window.h"
+#include "opencensus/tags/tag_key.h"

 namespace grpc {
 namespace load_reporter {
@ -38,12 +39,12 @@ CpuStatsProvider::CpuStatsSample CpuStatsProviderDefaultImpl::GetCpuStats() {
 }

 CensusViewProvider::CensusViewProvider()
-    : tag_key_token_(::opencensus::stats::TagKey::Register(kTagKeyToken)),
-      tag_key_host_(::opencensus::stats::TagKey::Register(kTagKeyHost)),
-      tag_key_user_id_(::opencensus::stats::TagKey::Register(kTagKeyUserId)),
-      tag_key_status_(::opencensus::stats::TagKey::Register(kTagKeyStatus)),
+    : tag_key_token_(::opencensus::tags::TagKey::Register(kTagKeyToken)),
+      tag_key_host_(::opencensus::tags::TagKey::Register(kTagKeyHost)),
+      tag_key_user_id_(::opencensus::tags::TagKey::Register(kTagKeyUserId)),
+      tag_key_status_(::opencensus::tags::TagKey::Register(kTagKeyStatus)),
      tag_key_metric_name_(
-          ::opencensus::stats::TagKey::Register(kTagKeyMetricName)) {
+          ::opencensus::tags::TagKey::Register(kTagKeyMetricName)) {
  // One view related to starting a call.
  auto vd_start_count =
      ::opencensus::stats::ViewDescriptor()
--- a/src/cpp/server/load_reporter/load_reporter.h
+++ b/src/cpp/server/load_reporter/load_reporter.h
@ -34,6 +34,7 @@
 #include "src/proto/grpc/lb/v1/load_reporter.grpc.pb.h"

 #include "opencensus/stats/stats.h"
+#include "opencensus/tags/tag_key.h"

 namespace grpc {
 namespace load_reporter {
@ -75,11 +76,11 @@ class CensusViewProvider {
 private:
  ViewDescriptorMap view_descriptor_map_;
  // Tag keys.
-  ::opencensus::stats::TagKey tag_key_token_;
-  ::opencensus::stats::TagKey tag_key_host_;
-  ::opencensus::stats::TagKey tag_key_user_id_;
-  ::opencensus::stats::TagKey tag_key_status_;
-  ::opencensus::stats::TagKey tag_key_metric_name_;
+  ::opencensus::tags::TagKey tag_key_token_;
+  ::opencensus::tags::TagKey tag_key_host_;
+  ::opencensus::tags::TagKey tag_key_user_id_;
+  ::opencensus::tags::TagKey tag_key_status_;
+  ::opencensus::tags::TagKey tag_key_metric_name_;
 };

 // The default implementation fetches the real stats from Census.
--- a/src/csharp/experimental/README.md
+++ b/src/csharp/experimental/README.md
@ -23,7 +23,7 @@ Unity and provide feedback!

 How to test gRPC in a Unity project

-1. Create a Unity project that targets .NET 4.x (Edit -> Project Settings -> Editor -> Scripting Runtime Version). gRPC uses APIs that are only available in .NET4.5+ so this is a requirement.
+1. Create a Unity project that targets .NET 4.x Equivalent (Edit -> Project Settings -> Player -> Configuration -> Scripting Runtime Version). gRPC uses APIs that are only available in .NET4.5+ so this is a requirement.

 2. Download the latest development build of `grpc_unity_package.VERSION.zip` from
   [daily builds](https://packages.grpc.io/)
--- a/src/objective-c/tests/BUILD
+++ b/src/objective-c/tests/BUILD
@ -63,9 +63,6 @@ grpc_objc_testing_library(
    data = [":TestCertificates"],
    defines = [
        "DEBUG=1",
-        "PB_FIELD_32BIT=1",
-        "PB_NO_PACKED_STRUCTS=1",
-        "PB_ENABLE_MALLOC=1",
        "HOST_PORT_LOCALSSL=localhost:5051",
        "HOST_PORT_LOCAL=localhost:5050",
        "HOST_PORT_REMOTE=grpc-test.sandbox.googleapis.com",
--- a/src/objective-c/tests/Tests.xcodeproj/project.pbxproj
+++ b/src/objective-c/tests/Tests.xcodeproj/project.pbxproj
@ -1721,9 +1721,6 @@
 					"$(inherited)",
 					"COCOAPODS=1",
 					"GPB_USE_PROTOBUF_FRAMEWORK_IMPORTS=1",
-					"PB_FIELD_32BIT=1",
-					"PB_NO_PACKED_STRUCTS=1",
-					"PB_ENABLE_MALLOC=1",
 					"GRPC_TEST_OBJC=1",
 				);
 				INFOPLIST_FILE = MacTests/Info.plist;
--- a/src/proto/grpc/testing/BUILD
+++ b/src/proto/grpc/testing/BUILD
@ -75,7 +75,7 @@ proto_library(

 py_proto_library(
    name = "empty_py_pb2",
-    srcs = [":empty_proto_descriptor"],
+    deps = [":empty_proto_descriptor"],
 )

 py_grpc_library(
@ -97,7 +97,7 @@ proto_library(

 py_proto_library(
    name = "py_messages_proto",
-    srcs = [":messages_proto_descriptor"],
+    deps = [":messages_proto_descriptor"],
 )

 py_grpc_library(
@ -206,7 +206,7 @@ proto_library(

 py_proto_library(
    name = "py_test_proto",
-    srcs = [":test_proto_descriptor"],
+    deps = [":test_proto_descriptor"],
 )

 py_grpc_library(
--- a/src/proto/grpc/testing/proto2/BUILD.bazel
+++ b/src/proto/grpc/testing/proto2/BUILD.bazel
@ -10,7 +10,7 @@ proto_library(

 py_proto_library(
    name = "empty2_proto",
-    srcs = [":empty2_proto_descriptor"],
+    deps = [":empty2_proto_descriptor"],
 )

 proto_library(
@ -23,6 +23,6 @@ proto_library(

 py_proto_library(
    name = "empty2_extensions_proto",
-    srcs = [":empty2_extensions_proto_descriptor"],
+    deps = [":empty2_extensions_proto_descriptor"],
 )

--- a/src/python/grpcio/grpc/init.py
+++ b/src/python/grpcio/grpc/init.py
@ -1747,6 +1747,64 @@ def dynamic_ssl_server_credentials(initial_certificate_configuration,
            certificate_configuration_fetcher, require_client_authentication))


+@enum.unique
+class LocalConnectionType(enum.Enum):
+    """Types of local connection for local credential creation.
+
+    Attributes:
+      UDS: Unix domain socket connections
+      LOCAL_TCP: Local TCP connections.
+    """
+    UDS = _cygrpc.LocalConnectionType.uds
+    LOCAL_TCP = _cygrpc.LocalConnectionType.local_tcp
+
+
+def local_channel_credentials(local_connect_type=LocalConnectionType.LOCAL_TCP):
+    """Creates a local ChannelCredentials used for local connections.
+
+    This is an EXPERIMENTAL API.
+
+    Local credentials are used by local TCP endpoints (e.g. localhost:10000)
+    also UDS connections. It allows them to create secure channel, hence
+    transmitting call credentials become possible.
+
+    It is useful for 1) eliminating insecure_channel usage; 2) enable unit
+    testing for call credentials without setting up secrets.
+
+    Args:
+      local_connect_type: Local connection type (either
+        grpc.LocalConnectionType.UDS or grpc.LocalConnectionType.LOCAL_TCP)
+
+    Returns:
+      A ChannelCredentials for use with a local Channel
+    """
+    return ChannelCredentials(
+        _cygrpc.channel_credentials_local(local_connect_type.value))
+
+
+def local_server_credentials(local_connect_type=LocalConnectionType.LOCAL_TCP):
+    """Creates a local ServerCredentials used for local connections.
+
+    This is an EXPERIMENTAL API.
+
+    Local credentials are used by local TCP endpoints (e.g. localhost:10000)
+    also UDS connections. It allows them to create secure channel, hence
+    transmitting call credentials become possible.
+
+    It is useful for 1) eliminating insecure_channel usage; 2) enable unit
+    testing for call credentials without setting up secrets.
+
+    Args:
+      local_connect_type: Local connection type (either
+        grpc.LocalConnectionType.UDS or grpc.LocalConnectionType.LOCAL_TCP)
+
+    Returns:
+      A ServerCredentials for use with a local Server
+    """
+    return ServerCredentials(
+        _cygrpc.server_credentials_local(local_connect_type.value))
+
+
 def channel_ready_future(channel):
    """Creates a Future that tracks when a Channel is ready.

@ -1916,6 +1974,7 @@ __all__ = (
    'ClientCallDetails',
    'ServerCertificateConfiguration',
    'ServerCredentials',
+    'LocalConnectionType',
    'UnaryUnaryMultiCallable',
    'UnaryStreamMultiCallable',
    'StreamUnaryMultiCallable',
@ -1942,6 +2001,8 @@ __all__ = (
    'access_token_call_credentials',
    'composite_call_credentials',
    'composite_channel_credentials',
+    'local_channel_credentials',
+    'local_server_credentials',
    'ssl_server_credentials',
    'ssl_server_certificate_configuration',
    'dynamic_ssl_server_credentials',
--- a/src/python/grpcio/grpc/_cython/_cygrpc/credentials.pxd.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/credentials.pxd.pxi
@ -97,3 +97,8 @@ cdef class ServerCredentials:
  cdef object cert_config_fetcher
  # whether C-core has asked for the initial_cert_config
  cdef bint initial_cert_config_fetched
+
+
+cdef class LocalChannelCredentials(ChannelCredentials):
+
+  cdef grpc_local_connect_type _local_connect_type
--- a/src/python/grpcio/grpc/_cython/_cygrpc/credentials.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/credentials.pyx.pxi
@ -328,3 +328,25 @@ cdef grpc_ssl_certificate_config_reload_status _server_cert_config_fetcher_wrapp
      cert_config.c_ssl_pem_key_cert_pairs_count)
  return GRPC_SSL_CERTIFICATE_CONFIG_RELOAD_NEW

+
+class LocalConnectionType:
+  uds = UDS
+  local_tcp = LOCAL_TCP
+
+cdef class LocalChannelCredentials(ChannelCredentials):
+
+  def __cinit__(self, grpc_local_connect_type local_connect_type):
+    self._local_connect_type = local_connect_type
+
+  cdef grpc_channel_credentials *c(self) except *:
+    cdef grpc_local_connect_type local_connect_type
+    local_connect_type = self._local_connect_type
+    return grpc_local_credentials_create(local_connect_type)
+
+def channel_credentials_local(grpc_local_connect_type local_connect_type):
+  return LocalChannelCredentials(local_connect_type)
+
+def server_credentials_local(grpc_local_connect_type local_connect_type):
+  cdef ServerCredentials credentials = ServerCredentials()
+  credentials.c_credentials = grpc_local_server_credentials_create(local_connect_type)
+  return credentials
--- a/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/grpc.pxi
@ -584,6 +584,12 @@ cdef extern from "grpc/grpc_security.h":

  void grpc_auth_context_release(grpc_auth_context *context)

+  grpc_channel_credentials *grpc_local_credentials_create(
+    grpc_local_connect_type type)
+  grpc_server_credentials *grpc_local_server_credentials_create(
+    grpc_local_connect_type type)
+
+
 cdef extern from "grpc/compression.h":

  ctypedef enum grpc_compression_algorithm:
@ -624,3 +630,9 @@ cdef extern from "grpc/impl/codegen/compression_types.h":

  const char *_GRPC_COMPRESSION_REQUEST_ALGORITHM_MD_KEY \
    "GRPC_COMPRESSION_REQUEST_ALGORITHM_MD_KEY"
+
+
+cdef extern from "grpc/grpc_security_constants.h":
+  ctypedef enum grpc_local_connect_type:
+    UDS
+    LOCAL_TCP
--- a/src/python/grpcio_channelz/grpc_channelz/v1/BUILD.bazel
+++ b/src/python/grpcio_channelz/grpc_channelz/v1/BUILD.bazel
@ -3,7 +3,7 @@ package(default_visibility = ["//visibility:public"])

 py_proto_library(
    name = "channelz_py_pb2",
-    srcs = ["//src/proto/grpc/channelz:channelz_proto_descriptors"],
+    deps = ["//src/proto/grpc/channelz:channelz_proto_descriptors"],
 )

 py_grpc_library(
--- a/src/python/grpcio_health_checking/grpc_health/v1/BUILD.bazel
+++ b/src/python/grpcio_health_checking/grpc_health/v1/BUILD.bazel
@ -3,7 +3,7 @@ package(default_visibility = ["//visibility:public"])

 py_proto_library(
    name = "health_py_pb2",
-    srcs = ["//src/proto/grpc/health/v1:health_proto_descriptor",],
+    deps = ["//src/proto/grpc/health/v1:health_proto_descriptor",],
 )

 py_grpc_library(
--- a/src/python/grpcio_reflection/grpc_reflection/v1alpha/BUILD.bazel
+++ b/src/python/grpcio_reflection/grpc_reflection/v1alpha/BUILD.bazel
@ -5,7 +5,7 @@ package(default_visibility = ["//visibility:public"])

 py_proto_library(
    name = "reflection_py_pb2",
-    srcs = ["//src/proto/grpc/reflection/v1alpha:reflection_proto_descriptor",],
+    deps = ["//src/proto/grpc/reflection/v1alpha:reflection_proto_descriptor",],
 )

 py_grpc_library(
--- a/src/python/grpcio_testing/grpc_testing/_server/_servicer_context.py
+++ b/src/python/grpcio_testing/grpc_testing/_server/_servicer_context.py
@ -74,7 +74,8 @@ class ServicerContext(grpc.ServicerContext):
            _common.fuss_with_metadata(trailing_metadata))

    def abort(self, code, details):
-        raise NotImplementedError()
+        with self._rpc._condition:
+            self._rpc._abort(code, details)

    def abort_with_status(self, status):
        raise NotImplementedError()
--- a/src/python/grpcio_tests/commands.py
+++ b/src/python/grpcio_tests/commands.py
@ -154,7 +154,9 @@ class TestGevent(setuptools.Command):
        'channelz._channelz_servicer_test.ChannelzServicerTest.test_many_subchannels_and_sockets',
        'channelz._channelz_servicer_test.ChannelzServicerTest.test_streaming_rpc',
        # TODO(https://github.com/grpc/grpc/issues/15411) enable this test
-        'unit._cython._channel_test.ChannelTest.test_negative_deadline_connectivity'
+        'unit._cython._channel_test.ChannelTest.test_negative_deadline_connectivity',
+        # TODO(https://github.com/grpc/grpc/issues/15411) enable this test
+        'unit._local_credentials_test.LocalCredentialsTest',
    )
    BANNED_WINDOWS_TESTS = (
        # TODO(https://github.com/grpc/grpc/pull/15411) enable this test
--- a/src/python/grpcio_tests/tests/tests.json
+++ b/src/python/grpcio_tests/tests/tests.json
@ -53,6 +53,7 @@
  "unit._interceptor_test.InterceptorTest",
  "unit._invalid_metadata_test.InvalidMetadataTest",
  "unit._invocation_defects_test.InvocationDefectsTest",
+  "unit._local_credentials_test.LocalCredentialsTest",
  "unit._logging_test.LoggingTest",
  "unit._metadata_code_details_test.MetadataCodeDetailsTest",
  "unit._metadata_flags_test.MetadataFlagsTest",
--- a/src/python/grpcio_tests/tests/unit/BUILD.bazel
+++ b/src/python/grpcio_tests/tests/unit/BUILD.bazel
@ -19,6 +19,7 @@ GRPCIO_TESTS_UNIT = [
    "_interceptor_test.py",
    "_invalid_metadata_test.py",
    "_invocation_defects_test.py",
+    "_local_credentials_test.py",
    "_logging_test.py",
    "_metadata_code_details_test.py",
    "_metadata_test.py",
--- a/src/python/grpcio_tests/tests/unit/_api_test.py
+++ b/src/python/grpcio_tests/tests/unit/_api_test.py
@ -60,6 +60,9 @@ class AllTest(unittest.TestCase):
            'ServiceRpcHandler',
            'Server',
            'ServerInterceptor',
+            'LocalConnectionType',
+            'local_channel_credentials',
+            'local_server_credentials',
            'unary_unary_rpc_method_handler',
            'unary_stream_rpc_method_handler',
            'stream_unary_rpc_method_handler',
--- a/src/python/grpcio_tests/tests/unit/_local_credentials_test.py
+++ b/src/python/grpcio_tests/tests/unit/_local_credentials_test.py
@ -0,0 +1,75 @@
+# Copyright 2019 The gRPC Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Test of RPCs made using local credentials."""
+
+import unittest
+import os
+from concurrent.futures import ThreadPoolExecutor
+import grpc
+
+
+class _GenericHandler(grpc.GenericRpcHandler):
+
+    def service(self, handler_call_details):
+        return grpc.unary_unary_rpc_method_handler(
+            lambda request, unused_context: request)
+
+
+class LocalCredentialsTest(unittest.TestCase):
+
+    def _create_server(self):
+        server = grpc.server(ThreadPoolExecutor())
+        server.add_generic_rpc_handlers((_GenericHandler(),))
+        return server
+
+    @unittest.skipIf(os.name == 'nt',
+                     'TODO(https://github.com/grpc/grpc/issues/20078)')
+    def test_local_tcp(self):
+        server_addr = 'localhost:{}'
+        channel_creds = grpc.local_channel_credentials(
+            grpc.LocalConnectionType.LOCAL_TCP)
+        server_creds = grpc.local_server_credentials(
+            grpc.LocalConnectionType.LOCAL_TCP)
+
+        server = self._create_server()
+        port = server.add_secure_port(server_addr.format(0), server_creds)
+        server.start()
+        with grpc.secure_channel(server_addr.format(port),
+                                 channel_creds) as channel:
+            self.assertEqual(b'abc',
+                             channel.unary_unary('/test/method')(
+                                 b'abc', wait_for_ready=True))
+        server.stop(None)
+
+    @unittest.skipIf(os.name == 'nt',
+                     'Unix Domain Socket is not supported on Windows')
+    def test_uds(self):
+        server_addr = 'unix:/tmp/grpc_fullstack_test'
+        channel_creds = grpc.local_channel_credentials(
+            grpc.LocalConnectionType.UDS)
+        server_creds = grpc.local_server_credentials(
+            grpc.LocalConnectionType.UDS)
+
+        server = self._create_server()
+        server.add_secure_port(server_addr, server_creds)
+        server.start()
+        with grpc.secure_channel(server_addr, channel_creds) as channel:
+            self.assertEqual(b'abc',
+                             channel.unary_unary('/test/method')(
+                                 b'abc', wait_for_ready=True))
+        server.stop(None)
+
+
+if __name__ == '__main__':
+    unittest.main()
--- a/templates/CMakeLists.txt.template
+++ b/templates/CMakeLists.txt.template
@ -145,8 +145,6 @@
  ## Some libraries are shared even with BUILD_SHARED_LIBRARIES=OFF
  set(CMAKE_POSITION_INDEPENDENT_CODE TRUE)
  
-  add_definitions(-DPB_FIELD_32BIT)
-
  if (MSVC)
    include(cmake/msvc_static_runtime.cmake)
    add_definitions(-D_WIN32_WINNT=0x600 -D_SCL_SECURE_NO_WARNINGS -D_CRT_SECURE_NO_WARNINGS -D_WINSOCK_DEPRECATED_NO_WARNINGS)
--- a/templates/Makefile.template
+++ b/templates/Makefile.template
@ -321,7 +321,7 @@
  endif

  GTEST_LIB = -Ithird_party/googletest/googletest/include -Ithird_party/googletest/googletest third_party/googletest/googletest/src/gtest-all.cc -Ithird_party/googletest/googlemock/include -Ithird_party/googletest/googlemock third_party/googletest/googlemock/src/gmock-all.cc
-  GTEST_LIB += -lgflags
+  GTEST_LIB += -lgflags -std=c++11
  ifeq ($(V),1)
  E = @:
  Q =
--- a/templates/config.m4.template
+++ b/templates/config.m4.template
@ -16,8 +16,8 @@

    LIBS="-lpthread $LIBS"

-    CFLAGS="-Wall -Werror -Wno-parentheses-equality -Wno-unused-value -std=c11 -g -O2 -D PB_FIELD_32BIT=1"
-    CXXFLAGS="-std=c++11 -fno-exceptions -fno-rtti -g -O2 -D PB_FIELD_32BIT=1"
+    CFLAGS="-Wall -Werror -Wno-parentheses-equality -Wno-unused-value -std=c11 -g -O2"
+    CXXFLAGS="-std=c++11 -fno-exceptions -fno-rtti -g -O2"
    GRPC_SHARED_LIBADD="-lpthread $GRPC_SHARED_LIBADD"
    PHP_REQUIRE_CXX()
    PHP_ADD_LIBRARY(pthread)
--- a/templates/config.w32.template
+++ b/templates/config.w32.template
@ -23,7 +23,6 @@
    EXTENSION("grpc", grpc_source, null,
      "/DOPENSSL_NO_ASM /D_GNU_SOURCE /DWIN32_LEAN_AND_MEAN "+
      "/D_HAS_EXCEPTIONS=0 /DNOMINMAX /DGRPC_ARES=0 /D_WIN32_WINNT=0x600 "+
-      "/DPB_FIELD_32BIT "+
      "/I"+configure_module_dirname+" "+
      "/I"+configure_module_dirname+"\\include "+
      "/I"+configure_module_dirname+"\\src\\core\\ext\\upb-generated "+
--- a/templates/gRPC-C++.podspec.template
+++ b/templates/gRPC-C++.podspec.template
@ -170,7 +170,7 @@
    s.pod_target_xcconfig = {
      'HEADER_SEARCH_PATHS' => '"$(inherited)" "$(PODS_TARGET_SRCROOT)/include"',
      'USER_HEADER_SEARCH_PATHS' => '"$(PODS_TARGET_SRCROOT)"',
-      'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1" "PB_NO_PACKED_STRUCTS=1"',
+      'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1"',
      'CLANG_WARN_STRICT_PROTOTYPES' => 'NO',
      'CLANG_WARN_DOCUMENTATION_COMMENTS' => 'NO',

--- a/templates/gRPC-Core.podspec.template
+++ b/templates/gRPC-Core.podspec.template
@ -144,12 +144,12 @@
      # build.
      'USE_HEADERMAP' => 'NO',
      'ALWAYS_SEARCH_USER_PATHS' => 'NO',
-      'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1" "PB_NO_PACKED_STRUCTS=1"',
+      'GCC_PREPROCESSOR_DEFINITIONS' => '"$(inherited)" "COCOAPODS=1"',
      'CLANG_WARN_STRICT_PROTOTYPES' => 'NO',
    }

    s.default_subspecs = 'Interface', 'Implementation'
-    s.compiler_flags = '-DGRPC_ARES=0', '-DPB_FIELD_32BIT'
+    s.compiler_flags = '-DGRPC_ARES=0'
    s.libraries = 'c++'

    # Like many other C libraries, gRPC-Core has its public headers under `include/<libname>/` and its
--- a/templates/tools/dockerfile/debian_testing_repo.include
+++ b/templates/tools/dockerfile/debian_testing_repo.include
@ -1,3 +0,0 @@
-# Add Debian 'testing' repository
-RUN echo 'deb http://ftp.de.debian.org/debian testing main' >> /etc/apt/sources.list
-RUN echo 'APT::Default-Release "stable";' | tee -a /etc/apt/apt.conf.d/00local
--- a/templates/tools/dockerfile/interoptest/grpc_interop_python/Dockerfile.template
+++ b/templates/tools/dockerfile/interoptest/grpc_interop_python/Dockerfile.template
@ -16,5 +16,5 @@
  
  <%include file="../../python_stretch.include"/>

-  RUN apt-get update && apt-get -t testing install -y python3.7 python3-all-dev
+  RUN apt-get update && apt-get -t stable install -y python3.7 python3-all-dev
  RUN curl https://bootstrap.pypa.io/get-pip.py | python3.7
--- a/templates/tools/dockerfile/python_stretch.include
+++ b/templates/tools/dockerfile/python_stretch.include
@ -3,7 +3,9 @@ FROM debian:stretch
 <%include file="./apt_get_basic.include"/>
 <%include file="./gcp_api_libraries.include"/>
 <%include file="./apt_get_python_27.include"/>
-<%include file="./debian_testing_repo.include"/>
+# Add Debian 'buster' repository, we will need it for installing newer versions of python
+RUN echo 'deb http://ftp.de.debian.org/debian buster main' >> /etc/apt/sources.list
+RUN echo 'APT::Default-Release "stretch";' | tee -a /etc/apt/apt.conf.d/00local
 <%include file="./run_tests_addons.include"/>
 # Define the default command.
 CMD ["bash"]
--- a/templates/tools/dockerfile/test/cxx_jessie_x86/Dockerfile.template
+++ b/templates/tools/dockerfile/test/cxx_jessie_x86/Dockerfile.template
@ -14,7 +14,7 @@
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
-  FROM 32bit/debian:jessie
+  FROM i386/debian:jessie
  RUN sed -i '/deb http:\/\/http.debian.net\/debian jessie-updates main/d' /etc/apt/sources.list
  
  <%include file="../../apt_get_basic.include"/>
--- a/templates/tools/dockerfile/test/python_stretch_3.6_x64/Dockerfile.template
+++ b/templates/tools/dockerfile/test/python_stretch_3.6_x64/Dockerfile.template
@ -16,5 +16,17 @@

  <%include file="../../python_stretch.include"/>

-  RUN apt-get update && apt-get -t testing install -y python3.6 python3-all-dev
-  RUN curl https://bootstrap.pypa.io/get-pip.py | python3.6
+  RUN apt-get install -y jq zlib1g-dev libssl-dev
+
+  RUN apt-get install -y jq build-essential libffi-dev
+
+  RUN cd /tmp && ${'\\'}
+    wget -q https://github.com/python/cpython/archive/v3.6.9.tar.gz && ${'\\'}
+    tar xzvf v3.6.9.tar.gz && ${'\\'}
+    cd cpython-3.6.9 && ${'\\'}
+    ./configure && ${'\\'}
+    make install
+
+  RUN python3.6 -m ensurepip && ${'\\'}
+      python3.6 -m pip install coverage
+
--- a/templates/tools/dockerfile/test/python_stretch_3.7_x64/Dockerfile.template
+++ b/templates/tools/dockerfile/test/python_stretch_3.7_x64/Dockerfile.template
@ -16,7 +16,7 @@

  <%include file="../../python_stretch.include"/>

-  RUN apt-get update && apt-get -t testing install -y python3.7 python3-all-dev
+  RUN apt-get update && apt-get -t buster install -y python3.7 python3-all-dev
  RUN curl https://bootstrap.pypa.io/get-pip.py | python3.7

  # for Python test coverage reporting
--- a/templates/tools/dockerfile/test/python_stretch_3.8_x64/Dockerfile.template
+++ b/templates/tools/dockerfile/test/python_stretch_3.8_x64/Dockerfile.template
@ -18,11 +18,14 @@
  <%include file="../../python_stretch.include"/>
  RUN apt-get install -y jq zlib1g-dev libssl-dev

-  COPY get_cpython.sh /tmp
-  RUN apt-get install -y jq build-essential libffi-dev && ${'\\'}
-    chmod +x /tmp/get_cpython.sh && ${'\\'}
-    /tmp/get_cpython.sh && ${'\\'}
-    rm /tmp/get_cpython.sh
+  RUN apt-get install -y jq build-essential libffi-dev
+
+  RUN cd /tmp && ${'\\'}
+    wget -q https://github.com/python/cpython/archive/v3.8.0b3.tar.gz && ${'\\'}
+    tar xzvf v3.8.0b3.tar.gz && ${'\\'}
+    cd cpython-3.8.0b3 && ${'\\'}
+    ./configure && ${'\\'}
+    make install

  RUN python3.8 -m ensurepip && ${'\\'}
      python3.8 -m pip install coverage
--- a/templates/tools/dockerfile/test/sanity/Dockerfile.template
+++ b/templates/tools/dockerfile/test/sanity/Dockerfile.template
@ -18,7 +18,7 @@
  <%include file="../../cxx_deps.include"/>
  #========================
  # Sanity test dependencies
-  RUN apt-get update && apt-get -t testing install -y python3.7 python3-all-dev
+  RUN apt-get update && apt-get -t buster install -y python3.7 python3-all-dev
  RUN curl https://bootstrap.pypa.io/get-pip.py | python3.7
  # Make Python 3.7 the default Python 3 version
  RUN update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.7 1
--- a/Show More
+++ b/Show More