First stab at config framework (#27014)

* First stab at config framework

* Automated change: Fix sanity tests

* add test for threaded initialization

* better test

* clang format

* better filenames

* Automated change: Fix sanity tests

Co-authored-by: ctiller <ctiller@users.noreply.github.com>

BUILD

@@ -783,6 +783,20 @@ grpc_cc_library(
     ],
 )
 
+grpc_cc_library(
+    name = "config",
+    srcs = [
+        "src/core/lib/config/core_configuration.cc",
+    ],
+    language = "c++",
+    public_hdrs = [
+        "src/core/lib/config/core_configuration.h",
+    ],
+    deps = [
+        "gpr_platform",
+    ],
+)
+
 grpc_cc_library(
     name = "debug_location",
     language = "c++",

CMakeLists.txt

@@ -843,6 +843,7 @@ if(gRPC_BUILD_TESTS)
   add_dependencies(buildtests_cxx connectivity_state_test)
   add_dependencies(buildtests_cxx context_allocator_end2end_test)
   add_dependencies(buildtests_cxx context_list_test)
+  add_dependencies(buildtests_cxx core_configuration_test)
   add_dependencies(buildtests_cxx delegating_channel_test)
   add_dependencies(buildtests_cxx destroy_grpclb_channel_with_active_connect_stress_test)
   add_dependencies(buildtests_cxx dual_ref_counted_test)
@@ -10233,6 +10234,41 @@ target_link_libraries(context_list_test
 )
 
 
+endif()
+if(gRPC_BUILD_TESTS)
+
+add_executable(core_configuration_test
+  src/core/lib/config/core_configuration.cc
+  test/core/config/core_configuration_test.cc
+  third_party/googletest/googletest/src/gtest-all.cc
+  third_party/googletest/googlemock/src/gmock-all.cc
+)
+
+target_include_directories(core_configuration_test
+  PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}
+    ${CMAKE_CURRENT_SOURCE_DIR}/include
+    ${_gRPC_ADDRESS_SORTING_INCLUDE_DIR}
+    ${_gRPC_RE2_INCLUDE_DIR}
+    ${_gRPC_SSL_INCLUDE_DIR}
+    ${_gRPC_UPB_GENERATED_DIR}
+    ${_gRPC_UPB_GRPC_GENERATED_DIR}
+    ${_gRPC_UPB_INCLUDE_DIR}
+    ${_gRPC_XXHASH_INCLUDE_DIR}
+    ${_gRPC_ZLIB_INCLUDE_DIR}
+    third_party/googletest/googletest/include
+    third_party/googletest/googletest
+    third_party/googletest/googlemock/include
+    third_party/googletest/googlemock
+    ${_gRPC_PROTO_GENS_DIR}
+)
+
+target_link_libraries(core_configuration_test
+  ${_gRPC_PROTOBUF_LIBRARIES}
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+)
+
+
 endif()
 if(gRPC_BUILD_TESTS)
 

build_autogenerated.yaml

@@ -5119,6 +5119,17 @@ targets:
   deps:
   - grpc_test_util
   uses_polling: false
+- name: core_configuration_test
+  gtest: true
+  build: test
+  language: c++
+  headers:
+  - src/core/lib/config/core_configuration.h
+  src:
+  - src/core/lib/config/core_configuration.cc
+  - test/core/config/core_configuration_test.cc
+  deps: []
+  uses_polling: false
 - name: delegating_channel_test
   gtest: true
   build: test

src/core/lib/config/core_configuration.cc

@@ -0,0 +1,53 @@
+// Copyright 2021 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.
+
+#include <grpc/impl/codegen/port_platform.h>
+
+#include "src/core/lib/config/core_configuration.h"
+
+namespace grpc_core {
+
+std::atomic<CoreConfiguration*> CoreConfiguration::config_;
+
+CoreConfiguration::Builder::Builder() = default;
+
+CoreConfiguration* CoreConfiguration::Builder::Build() {
+  return new CoreConfiguration;
+}
+
+CoreConfiguration::CoreConfiguration() = default;
+
+const CoreConfiguration& CoreConfiguration::BuildNewAndMaybeSet() {
+  // Construct builder, pass it up to code that knows about build configuration
+  Builder builder;
+  BuildCoreConfiguration(&builder);
+  // Use builder to construct a confguration
+  CoreConfiguration* p = builder.Build();
+  // Try to set configuration global - it's possible another thread raced us
+  // here, in which case we drop the work we did and use the one that got set
+  // first
+  CoreConfiguration* expected = nullptr;
+  if (!config_.compare_exchange_strong(expected, p,
+                                       std::memory_order_release)) {
+    delete p;
+    return *expected;
+  }
+  return *p;
+}
+
+void CoreConfiguration::Reset() {
+  delete config_.exchange(nullptr, std::memory_order_acquire);
+}
+
+}  // namespace grpc_core

src/core/lib/config/core_configuration.h

@@ -0,0 +1,74 @@
+// Copyright 2021 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.
+
+#ifndef GRPC_CORE_LIB_CONFIG_CORE_CONFIGURATION_H
+#define GRPC_CORE_LIB_CONFIG_CORE_CONFIGURATION_H
+
+#include <grpc/impl/codegen/port_platform.h>
+
+#include <atomic>
+
+namespace grpc_core {
+
+// Global singleton that stores library configuration - factories, etc...
+// that plugins might choose to extend.
+class CoreConfiguration {
+ public:
+  CoreConfiguration(const CoreConfiguration&) = delete;
+  CoreConfiguration& operator=(const CoreConfiguration&) = delete;
+
+  // Builder is passed to plugins, etc... at initialization time to collect
+  // their configuration and assemble the published CoreConfiguration.
+  class Builder {
+   public:
+   private:
+    friend class CoreConfiguration;
+
+    Builder();
+    CoreConfiguration* Build();
+  };
+
+  // Lifetime methods
+
+  // Get the core configuration; if it does not exist, create it.
+  static const CoreConfiguration& Get() {
+    CoreConfiguration* p = config_.load(std::memory_order_acquire);
+    if (p != nullptr) {
+      return *p;
+    }
+    return BuildNewAndMaybeSet();
+  }
+
+  // Drop the core configuration. Users must ensure no other threads are
+  // accessing the configuration.
+  static void Reset();
+
+  // Accessors
+
+ private:
+  CoreConfiguration();
+
+  // Create a new CoreConfiguration, and either set it or throw it away.
+  // We allow multiple CoreConfiguration's to be created in parallel.
+  static const CoreConfiguration& BuildNewAndMaybeSet();
+
+  // The configuration
+  static std::atomic<CoreConfiguration*> config_;
+};
+
+extern void BuildCoreConfiguration(CoreConfiguration::Builder* builder);
+
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_LIB_CONFIG_CORE_CONFIGURATION_H */

test/core/config/BUILD

@@ -0,0 +1,31 @@
+# Copyright 2021 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.
+
+load("//bazel:grpc_build_system.bzl", "grpc_cc_test", "grpc_package")
+
+licenses(["notice"])
+
+grpc_package(name = "test/core/config")
+
+grpc_cc_test(
+    name = "core_configuration_test",
+    srcs = ["core_configuration_test.cc"],
+    external_deps = ["gtest"],
+    language = "c++",
+    uses_polling = False,
+    deps = [
+        "//:config",
+        "//test/core/util:grpc_suppressions",
+    ],
+)

test/core/config/core_configuration_test.cc

@@ -0,0 +1,71 @@
+// Copyright 2021 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.
+
+#include "src/core/lib/config/core_configuration.h"
+#include <gtest/gtest.h>
+#include <chrono>
+#include <thread>
+
+namespace grpc_core {
+
+// Allow substitution of config builder - in real code this would iterate
+// through all plugins
+namespace testing {
+using ConfigBuilderFunction = std::function<void(CoreConfiguration::Builder*)>;
+static ConfigBuilderFunction g_mock_builder;
+}  // namespace testing
+
+void BuildCoreConfiguration(CoreConfiguration::Builder* builder) {
+  ::grpc_core::testing::g_mock_builder(builder);
+}
+
+namespace testing {
+// Helper for testing - clear out any state, rebuild configuration with fn being
+// the initializer
+void InitConfigWithBuilder(ConfigBuilderFunction fn) {
+  CoreConfiguration::Reset();
+  g_mock_builder = fn;
+  CoreConfiguration::Get();
+  g_mock_builder = nullptr;
+}
+
+TEST(ConfigTest, NoopConfig) {
+  InitConfigWithBuilder([](CoreConfiguration::Builder*) {});
+  CoreConfiguration::Get();
+}
+
+TEST(ConfigTest, ThreadedInit) {
+  CoreConfiguration::Reset();
+  g_mock_builder = [](CoreConfiguration::Builder*) {
+    std::this_thread::sleep_for(std::chrono::seconds(1));
+  };
+  std::vector<std::thread> threads;
+  threads.reserve(64);
+  for (int i = 0; i < 64; i++) {
+    threads.push_back(std::thread([]() { CoreConfiguration::Get(); }));
+  }
+  for (auto& t : threads) {
+    t.join();
+  }
+  g_mock_builder = nullptr;
+  CoreConfiguration::Get();
+}
+}  // namespace testing
+
+}  // namespace grpc_core
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}

tools/run_tests/generated/tests.json

@@ -4369,6 +4369,30 @@
     ],
     "uses_polling": false
   },
+  {
+    "args": [],
+    "benchmark": false,
+    "ci_platforms": [
+      "linux",
+      "mac",
+      "posix",
+      "windows"
+    ],
+    "cpu_cost": 1.0,
+    "exclude_configs": [],
+    "exclude_iomgrs": [],
+    "flaky": false,
+    "gtest": true,
+    "language": "c++",
+    "name": "core_configuration_test",
+    "platforms": [
+      "linux",
+      "mac",
+      "posix",
+      "windows"
+    ],
+    "uses_polling": false
+  },
   {
     "args": [],
     "benchmark": false,