[OTel] Generate pkg-config file for grpcpp_otel_plugin (#36686)

Public Changes -
* Add a pkgconfig installer for `grpcpp_otel_plugin`

Example Changes -
* Add example of how to use the pkgconfig for `grpcpp_otel_plugin` with the existing OpenTelemetry example.
* Add another OpenTelemetry example that uses OTel's OStream exporter. This makes it easier to test the pkgconfig file for `grpcpp_otel_plugin` since the OStream exporter does not require any additional dependencies, as opposed to the Prometheus exporter.

Test changes -
* Modify `run_distrib_test_cmake_pkgconfig.sh` test to install opentelemetry and build the example with the OStream exporter.

Closes #36686

PiperOrigin-RevId: 636965475

CMakeLists.txt

@@ -37015,3 +37015,14 @@ generate_pkgconfig(
   "-lgrpc++_unsecure"
   "-laddress_sorting -lupb_message_lib -lupb_mem_lib -lupb_base_lib -lutf8_range_lib"
   "grpc++_unsecure.pc")
+
+# grpcpp_otel_plugin .pc file
+generate_pkgconfig(
+  "gRPC++ OpenTelemetry Plugin"
+  "OpenTelemetry Plugin for gRPC C++"
+  "${gRPC_CPP_VERSION}"
+  "absl_algorithm_container absl_any_invocable absl_base absl_bind_front absl_check absl_cleanup absl_config absl_cord absl_core_headers absl_flags absl_flags_marshalling absl_flat_hash_map absl_flat_hash_set absl_function_ref absl_hash absl_inlined_vector absl_log absl_log_globals absl_log_severity absl_memory absl_no_destructor absl_optional absl_random_bit_gen_ref absl_random_distributions absl_random_random absl_span absl_status absl_statusor absl_str_format absl_strings absl_synchronization absl_time absl_type_traits absl_utility absl_variant gpr grpc grpc++ opentelemetry_api"
+  "libcares openssl re2 zlib"
+  "-lgrpcpp_otel_plugin"
+  "-laddress_sorting -lupb_textformat_lib -lupb_json_lib -lupb_message_lib -lupb_mem_lib -lupb_base_lib -lutf8_range_lib"
+  "grpcpp_otel_plugin.pc")

examples/cpp/otel/BUILD

@@ -14,12 +14,19 @@
 
 licenses(["notice"])
 
+package(
+    default_visibility = ["//examples/cpp/otel:__subpackages__"],
+)
+
 cc_library(
     name = "util",
     srcs = ["util.cc"],
     hdrs = ["util.h"],
+    defines = ["BAZEL_BUILD"],
     deps = [
         "//:grpc++",
+        "//:grpc++_reflection",
+        "//examples/protos:helloworld_cc_grpc",
         "@io_opentelemetry_cpp//sdk/src/metrics",
     ],
 )
@@ -32,7 +39,6 @@ cc_binary(
         "util",
         "//:grpc++",
         "//:grpcpp_otel_plugin",
-        "//examples/protos:helloworld_cc_grpc",
         "@com_google_absl//absl/flags:flag",
         "@com_google_absl//absl/flags:parse",
         "@io_opentelemetry_cpp//exporters/prometheus:prometheus_exporter",
@@ -47,9 +53,7 @@ cc_binary(
     deps = [
         "util",
         "//:grpc++",
-        "//:grpc++_reflection",
         "//:grpcpp_otel_plugin",
-        "//examples/protos:helloworld_cc_grpc",
         "@com_google_absl//absl/flags:flag",
         "@com_google_absl//absl/flags:parse",
         "@com_google_absl//absl/strings:str_format",

examples/cpp/otel/CMakeLists.txt

@@ -67,22 +67,21 @@ target_link_libraries(hw_grpc_proto
 add_library(util
   "util.cc")
 target_link_libraries(util
+  hw_grpc_proto
   opentelemetry-cpp::metrics
-  ${_GRPC_GRPCPP})
+  ${_GRPC_GRPCPP}
+  ${_REFLECTION}
+  ${_PROTOBUF_LIBPROTOBUF})
 
 # Targets greeter_callback_(client|server)
 foreach(_target
   greeter_callback_client greeter_callback_server)
   add_executable(${_target} "${_target}.cc")
   target_link_libraries(${_target}
-    hw_grpc_proto
     absl::flags
     absl::flags_parse
     opentelemetry-cpp::metrics
     opentelemetry-cpp::prometheus_exporter
-    ${_REFLECTION}
-    ${_GRPC_GRPCPP}
     gRPC::grpcpp_otel_plugin
-    util
+    util)
-    ${_PROTOBUF_LIBPROTOBUF})
 endforeach()

examples/cpp/otel/Makefile

@@ -0,0 +1,124 @@
+#
+# Copyright 2015 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.
+#
+
+# TODO(jtattermusch): Remove the hack to workaround protobuf bug. See https://github.com/protocolbuffers/protobuf/issues/12439
+# Hack: protobuf currently doesn't declare it's absl dependencies when protobuf.pc pkgconfig file is used.
+PROTOBUF_ABSL_DEPS = absl_absl_check absl_absl_log absl_algorithm absl_base absl_bind_front absl_bits absl_btree absl_cleanup absl_cord absl_core_headers absl_debugging absl_die_if_null absl_dynamic_annotations absl_flags absl_flat_hash_map absl_flat_hash_set absl_function_ref absl_hash absl_layout absl_log_initialize absl_log_severity absl_memory absl_node_hash_map absl_node_hash_set absl_optional absl_span absl_status absl_statusor absl_strings absl_synchronization absl_time absl_type_traits absl_utility absl_variant
+# TODO(jtattermusch): Remove the hack to workaround protobuf/utf8_range bug. See https://github.com/protocolbuffers/utf8_range/issues/20
+# Hack: utf8_range (which is protobuf's dependency) currently doesn't have a pkgconfig file, so we need to explicitly
+# tweak the list of libraries to link against to fix the build.
+PROTOBUF_UTF8_RANGE_LINK_LIBS = -lutf8_validity
+OPENTELEMETRY_LINK_LIBS = -lopentelemetry_metrics -lopentelemetry_exporter_prometheus -lopentelemetry_common -lopentelemetry_resources -lprometheus-cpp-pull -lprometheus-cpp-core
+
+HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
+SYSTEM ?= $(HOST_SYSTEM)
+CXX = g++
+CPPFLAGS += `pkg-config --cflags protobuf grpc absl_flags absl_flags_parse`
+ifeq ($(SYSTEM),Darwin)
+LDFLAGS += -L/usr/local/lib `pkg-config --libs --static protobuf grpc++ grpcpp_otel_plugin absl_flags absl_flags_parse $(PROTOBUF_ABSL_DEPS)` \
+           $(PROTOBUF_UTF8_RANGE_LINK_LIBS) \
+	       $(OPENTELEMETRY_LINK_LIBS) \
+           -pthread \
+           -lgrpc++_reflection \
+           -ldl
+else
+LDFLAGS += -L/usr/local/lib `pkg-config --libs --static protobuf grpc++ grpcpp_otel_plugin absl_flags absl_flags_parse $(PROTOBUF_ABSL_DEPS)` \
+           $(PROTOBUF_UTF8_RANGE_LINK_LIBS) \
+	       $(OPENTELEMETRY_LINK_LIBS) \
+           -pthread \
+           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed \
+           -ldl
+endif
+PROTOC = protoc
+GRPC_CPP_PLUGIN = grpc_cpp_plugin
+GRPC_CPP_PLUGIN_PATH ?= `which $(GRPC_CPP_PLUGIN)`
+
+PROTOS_PATH = ../../protos
+
+vpath %.proto $(PROTOS_PATH)
+
+all: system-check greeter_callback_client greeter_callback_server
+
+greeter_callback_client: util.o helloworld.pb.o helloworld.grpc.pb.o greeter_callback_client.o
+	$(CXX) $^ $(LDFLAGS) -o $@
+
+greeter_callback_server: util.o helloworld.pb.o helloworld.grpc.pb.o greeter_callback_server.o
+	$(CXX) $^ $(LDFLAGS) -o $@
+
+.PRECIOUS: %.grpc.pb.cc
+%.grpc.pb.cc: %.proto
+	$(PROTOC) -I $(PROTOS_PATH) --grpc_out=. --plugin=protoc-gen-grpc=$(GRPC_CPP_PLUGIN_PATH) $<
+
+.PRECIOUS: %.pb.cc
+%.pb.cc: %.proto
+	$(PROTOC) -I $(PROTOS_PATH) --cpp_out=. $<
+
+clean:
+	rm -f *.o *.pb.cc *.pb.h greeter_callback_client greeter_callback_server
+
+
+# The following is to test your system and ensure a smoother experience.
+# They are by no means necessary to actually compile a grpc-enabled software.
+
+PROTOC_CMD = which $(PROTOC)
+PROTOC_CHECK_CMD = $(PROTOC) --version | grep -q 'libprotoc.3\|libprotoc [0-9][0-9]\.'
+PLUGIN_CHECK_CMD = which $(GRPC_CPP_PLUGIN)
+HAS_PROTOC = $(shell $(PROTOC_CMD) > /dev/null && echo true || echo false)
+ifeq ($(HAS_PROTOC),true)
+HAS_VALID_PROTOC = $(shell $(PROTOC_CHECK_CMD) 2> /dev/null && echo true || echo false)
+endif
+HAS_PLUGIN = $(shell $(PLUGIN_CHECK_CMD) > /dev/null && echo true || echo false)
+
+SYSTEM_OK = false
+ifeq ($(HAS_VALID_PROTOC),true)
+ifeq ($(HAS_PLUGIN),true)
+SYSTEM_OK = true
+endif
+endif
+
+system-check:
+ifneq ($(HAS_VALID_PROTOC),true)
+	@echo " DEPENDENCY ERROR"
+	@echo
+	@echo "You don't have protoc 3.0.0 or newer installed in your path."
+	@echo "Please install an up-to-date version of Google protocol buffers."
+	@echo "You can find it here:"
+	@echo
+	@echo "   https://github.com/protocolbuffers/protobuf/releases"
+	@echo
+	@echo "Here is what I get when trying to evaluate your version of protoc:"
+	@echo
+	-$(PROTOC) --version
+	@echo
+	@echo
+endif
+ifneq ($(HAS_PLUGIN),true)
+	@echo " DEPENDENCY ERROR"
+	@echo
+	@echo "You don't have the grpc c++ protobuf plugin installed in your path."
+	@echo "Please install grpc. You can find it here:"
+	@echo
+	@echo "   https://github.com/grpc/grpc"
+	@echo
+	@echo "Here is what I get when trying to detect if you have the plugin:"
+	@echo
+	-which $(GRPC_CPP_PLUGIN)
+	@echo
+	@echo
+endif
+ifneq ($(SYSTEM_OK),true)
+	@false
+endif

examples/cpp/otel/greeter_callback_client.cc

@@ -16,12 +16,14 @@
  *
  */
 
-#include <condition_variable>
+// Explicitly define HAVE_ABSEIL to avoid conflict with OTel's Abseil
-#include <iostream>
+// version. Refer
-#include <memory>
+// https://github.com/open-telemetry/opentelemetry-cpp/issues/1042.
-#include <mutex>
+#ifndef HAVE_ABSEIL
+#define HAVE_ABSEIL
+#endif
+
 #include <string>
-#include <thread>
 
 #include "absl/flags/flag.h"
 #include "absl/flags/parse.h"
@@ -30,13 +32,10 @@
 #include "opentelemetry/sdk/metrics/meter_provider.h"
 
 #include <grpcpp/ext/otel_plugin.h>
-#include <grpcpp/grpcpp.h>
 
 #ifdef BAZEL_BUILD
 #include "examples/cpp/otel/util.h"
-#include "examples/protos/helloworld.grpc.pb.h"
 #else
-#include "helloworld.grpc.pb.h"
 #include "util.h"
 #endif
 
@@ -44,64 +43,6 @@ ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
 ABSL_FLAG(std::string, prometheus_endpoint, "localhost:9465",
           "Prometheus exporter endpoint");
 
-using grpc::Channel;
-using grpc::ClientContext;
-using grpc::Status;
-using helloworld::Greeter;
-using helloworld::HelloReply;
-using helloworld::HelloRequest;
-
-class GreeterClient {
- public:
-  GreeterClient(std::shared_ptr<Channel> channel)
-      : stub_(Greeter::NewStub(channel)) {}
-
-  // Assembles the client's payload, sends it and presents the response back
-  // from the server.
-  std::string SayHello(const std::string& user) {
-    // Data we are sending to the server.
-    HelloRequest request;
-    request.set_name(user);
-
-    // Container for the data we expect from the server.
-    HelloReply reply;
-
-    // Context for the client. It could be used to convey extra information to
-    // the server and/or tweak certain RPC behaviors.
-    ClientContext context;
-
-    // The actual RPC.
-    std::mutex mu;
-    std::condition_variable cv;
-    bool done = false;
-    Status status;
-    stub_->async()->SayHello(&context, &request, &reply,
-                             [&mu, &cv, &done, &status](Status s) {
-                               status = std::move(s);
-                               std::lock_guard<std::mutex> lock(mu);
-                               done = true;
-                               cv.notify_one();
-                             });
-
-    std::unique_lock<std::mutex> lock(mu);
-    while (!done) {
-      cv.wait(lock);
-    }
-
-    // Act upon its status.
-    if (status.ok()) {
-      return reply.message();
-    } else {
-      std::cout << status.error_code() << ": " << status.error_message()
-                << std::endl;
-      return "RPC failed";
-    }
-  }
-
- private:
-  std::unique_ptr<Greeter::Stub> stub_;
-};
-
 int main(int argc, char** argv) {
   absl::ParseCommandLine(argc, argv);
   // Register a global gRPC OpenTelemetry plugin configured with a prometheus
@@ -125,20 +66,9 @@ int main(int argc, char** argv) {
               << status.ToString() << std::endl;
     return static_cast<int>(status.code());
   }
-  // Instantiate the client. It requires a channel, out of which the actual RPCs
+
-  // are created. This channel models a connection to an endpoint specified by
-  // the argument "--target=" which is the only expected argument.
-  std::string target_str = absl::GetFlag(FLAGS_target);
-  grpc::ChannelArguments args;
   // Continuously send RPCs every second.
-  while (true) {
+  RunClient(absl::GetFlag(FLAGS_target));
-    GreeterClient greeter(grpc::CreateCustomChannel(
-        target_str, grpc::InsecureChannelCredentials(), args));
-    std::string user("world");
-    std::string reply = greeter.SayHello(user);
-    std::cout << "Greeter received: " << reply << std::endl;
-    std::this_thread::sleep_for(std::chrono::seconds(1));
-  }
 
   return 0;
 }

examples/cpp/otel/greeter_callback_server.cc

@@ -16,6 +16,13 @@
  *
  */
 
+// Explicitly define HAVE_ABSEIL to avoid conflict with OTel's Abseil
+// version. Refer
+// https://github.com/open-telemetry/opentelemetry-cpp/issues/1042.
+#ifndef HAVE_ABSEIL
+#define HAVE_ABSEIL
+#endif
+
 #include <iostream>
 #include <memory>
 #include <string>
@@ -28,15 +35,10 @@
 #include "opentelemetry/sdk/metrics/meter_provider.h"
 
 #include <grpcpp/ext/otel_plugin.h>
-#include <grpcpp/ext/proto_server_reflection_plugin.h>
-#include <grpcpp/grpcpp.h>
-#include <grpcpp/health_check_service_interface.h>
 
 #ifdef BAZEL_BUILD
 #include "examples/cpp/otel/util.h"
-#include "examples/protos/helloworld.grpc.pb.h"
 #else
-#include "helloworld.grpc.pb.h"
 #include "util.h"
 #endif
 
@@ -44,50 +46,6 @@ ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
 ABSL_FLAG(std::string, prometheus_endpoint, "localhost:9464",
           "Prometheus exporter endpoint");
 
-using grpc::CallbackServerContext;
-using grpc::Server;
-using grpc::ServerBuilder;
-using grpc::ServerUnaryReactor;
-using grpc::Status;
-using helloworld::Greeter;
-using helloworld::HelloReply;
-using helloworld::HelloRequest;
-
-// Logic and data behind the server's behavior.
-class GreeterServiceImpl final : public Greeter::CallbackService {
-  ServerUnaryReactor* SayHello(CallbackServerContext* context,
-                               const HelloRequest* request,
-                               HelloReply* reply) override {
-    std::string prefix("Hello ");
-    reply->set_message(prefix + request->name());
-
-    ServerUnaryReactor* reactor = context->DefaultReactor();
-    reactor->Finish(Status::OK);
-    return reactor;
-  }
-};
-
-void RunServer(uint16_t port) {
-  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
-  GreeterServiceImpl service;
-
-  grpc::EnableDefaultHealthCheckService(true);
-  grpc::reflection::InitProtoReflectionServerBuilderPlugin();
-  ServerBuilder builder;
-  // Listen on the given address without any authentication mechanism.
-  builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
-  // Register "service" as the instance through which we'll communicate with
-  // clients. In this case it corresponds to an *synchronous* service.
-  builder.RegisterService(&service);
-  // Finally assemble the server.
-  std::unique_ptr<Server> server(builder.BuildAndStart());
-  std::cout << "Server listening on " << server_address << std::endl;
-
-  // Wait for the server to shutdown. Note that some other thread must be
-  // responsible for shutting down the server for this call to ever return.
-  server->Wait();
-}
-
 int main(int argc, char** argv) {
   absl::ParseCommandLine(argc, argv);
   // Register a global gRPC OpenTelemetry plugin configured with a prometheus

examples/cpp/otel/ostream/BUILD

@@ -0,0 +1,44 @@
+# Copyright 2023 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.
+
+licenses(["notice"])
+
+cc_binary(
+    name = "greeter_callback_client",
+    srcs = ["greeter_callback_client.cc"],
+    defines = ["BAZEL_BUILD"],
+    deps = [
+        "//:grpcpp_otel_plugin",
+        "//examples/cpp/otel:util",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@io_opentelemetry_cpp//exporters/ostream:ostream_metric_exporter",
+        "@io_opentelemetry_cpp//sdk/src/metrics",
+    ],
+)
+
+cc_binary(
+    name = "greeter_callback_server",
+    srcs = ["greeter_callback_server.cc"],
+    defines = ["BAZEL_BUILD"],
+    deps = [
+        "//:grpcpp_otel_plugin",
+        "//examples/cpp/otel:util",
+        "@com_google_absl//absl/flags:flag",
+        "@com_google_absl//absl/flags:parse",
+        "@com_google_absl//absl/strings:str_format",
+        "@io_opentelemetry_cpp//exporters/ostream:ostream_metric_exporter",
+        "@io_opentelemetry_cpp//sdk/src/metrics",
+    ],
+)

examples/cpp/otel/ostream/CMakeLists.txt

@@ -0,0 +1,85 @@
+# Copyright 2018 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.
+#
+# cmake build file for C++ gRPC OpenTelemetry example.
+# Assumes absl, protobuf, prometheus-cpp, opentelemetry-cpp and gRPC (with -DgRPC_BUILD_OPENTELEMETRY_PLUGIN=ON) have been installed using cmake.
+# See cmake_externalproject/CMakeLists.txt for all-in-one cmake build
+# that automatically builds all the dependencies before building helloworld.
+
+cmake_minimum_required(VERSION 3.13)
+
+project(grpc_opentelemetry_example C CXX)
+
+include(../../cmake/common.cmake)
+
+# Find opentelemetry-cpp package
+find_package(opentelemetry-cpp CONFIG REQUIRED)
+
+# Proto file
+get_filename_component(hw_proto "../../../protos/helloworld.proto" ABSOLUTE)
+get_filename_component(hw_proto_path "${hw_proto}" PATH)
+
+# Generated sources
+set(hw_proto_srcs "${CMAKE_CURRENT_BINARY_DIR}/helloworld.pb.cc")
+set(hw_proto_hdrs "${CMAKE_CURRENT_BINARY_DIR}/helloworld.pb.h")
+set(hw_grpc_srcs "${CMAKE_CURRENT_BINARY_DIR}/helloworld.grpc.pb.cc")
+set(hw_grpc_hdrs "${CMAKE_CURRENT_BINARY_DIR}/helloworld.grpc.pb.h")
+add_custom_command(
+      OUTPUT "${hw_proto_srcs}" "${hw_proto_hdrs}" "${hw_grpc_srcs}" "${hw_grpc_hdrs}"
+      COMMAND ${_PROTOBUF_PROTOC}
+      ARGS --grpc_out "${CMAKE_CURRENT_BINARY_DIR}"
+        --cpp_out "${CMAKE_CURRENT_BINARY_DIR}"
+        -I "${hw_proto_path}"
+        --plugin=protoc-gen-grpc="${_GRPC_CPP_PLUGIN_EXECUTABLE}"
+        "${hw_proto}"
+      DEPENDS "${hw_proto}")
+
+# Include generated *.pb.h files
+include_directories("${CMAKE_CURRENT_BINARY_DIR}")
+include_directories("${CMAKE_SOURCE_DIR}")
+
+# hw_grpc_proto
+add_library(hw_grpc_proto
+  ${hw_grpc_srcs}
+  ${hw_grpc_hdrs}
+  ${hw_proto_srcs}
+  ${hw_proto_hdrs})
+target_link_libraries(hw_grpc_proto
+  ${_REFLECTION}
+  ${_GRPC_GRPCPP}
+  ${_PROTOBUF_LIBPROTOBUF})
+
+# util
+add_library(util
+  "../util.cc")
+target_link_libraries(util
+  hw_grpc_proto
+  opentelemetry-cpp::metrics
+  ${_GRPC_GRPCPP}
+  ${_REFLECTION}
+  ${_PROTOBUF_LIBPROTOBUF})
+
+# Targets greeter_callback_(client|server)
+foreach(_target
+  greeter_callback_client greeter_callback_server)
+  add_executable(${_target} "${_target}.cc")
+  target_link_libraries(${_target}
+    absl::flags
+    absl::flags_parse
+    opentelemetry-cpp::metrics
+    opentelemetry-cpp::ostream_metrics_exporter
+    gRPC::grpcpp_otel_plugin
+    util
+    ${_PROTOBUF_LIBPROTOBUF})
+endforeach()

examples/cpp/otel/ostream/Makefile

@@ -0,0 +1,127 @@
+#
+# Copyright 2015 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.
+#
+
+# TODO(jtattermusch): Remove the hack to workaround protobuf bug. See https://github.com/protocolbuffers/protobuf/issues/12439
+# Hack: protobuf currently doesn't declare it's absl dependencies when protobuf.pc pkgconfig file is used.
+PROTOBUF_ABSL_DEPS = absl_absl_check absl_absl_log absl_algorithm absl_base absl_bind_front absl_bits absl_btree absl_cleanup absl_cord absl_core_headers absl_debugging absl_die_if_null absl_dynamic_annotations absl_flags absl_flat_hash_map absl_flat_hash_set absl_function_ref absl_hash absl_layout absl_log_initialize absl_log_severity absl_memory absl_node_hash_map absl_node_hash_set absl_optional absl_span absl_status absl_statusor absl_strings absl_synchronization absl_time absl_type_traits absl_utility absl_variant
+# TODO(jtattermusch): Remove the hack to workaround protobuf/utf8_range bug. See https://github.com/protocolbuffers/utf8_range/issues/20
+# Hack: utf8_range (which is protobuf's dependency) currently doesn't have a pkgconfig file, so we need to explicitly
+# tweak the list of libraries to link against to fix the build.
+PROTOBUF_UTF8_RANGE_LINK_LIBS = -lutf8_validity
+OPENTELEMETRY_LINK_LIBS = -lopentelemetry_metrics -lopentelemetry_exporter_ostream_metrics -lopentelemetry_resources -lopentelemetry_common
+
+HOST_SYSTEM = $(shell uname | cut -f 1 -d_)
+SYSTEM ?= $(HOST_SYSTEM)
+CXX = g++
+CPPFLAGS += `pkg-config --cflags protobuf grpc absl_flags absl_flags_parse`
+ifeq ($(SYSTEM),Darwin)
+LDFLAGS += -L/usr/local/lib `pkg-config --libs --static protobuf grpc++ grpcpp_otel_plugin absl_flags absl_flags_parse $(PROTOBUF_ABSL_DEPS)` \
+           $(PROTOBUF_UTF8_RANGE_LINK_LIBS) \
+	       $(OPENTELEMETRY_LINK_LIBS) \
+           -pthread \
+           -lgrpc++_reflection \
+           -ldl
+else
+LDFLAGS += -L/usr/local/lib `pkg-config --libs --static protobuf grpc++ grpcpp_otel_plugin absl_flags absl_flags_parse $(PROTOBUF_ABSL_DEPS)` \
+           $(PROTOBUF_UTF8_RANGE_LINK_LIBS) \
+	       $(OPENTELEMETRY_LINK_LIBS) \
+           -pthread \
+           -Wl,--no-as-needed -lgrpc++_reflection -Wl,--as-needed \
+           -ldl
+endif
+PROTOC = protoc
+GRPC_CPP_PLUGIN = grpc_cpp_plugin
+GRPC_CPP_PLUGIN_PATH ?= `which $(GRPC_CPP_PLUGIN)`
+
+PROTOS_PATH = ../../../protos
+
+vpath %.proto $(PROTOS_PATH)
+
+all: system-check greeter_callback_client greeter_callback_server
+
+greeter_callback_client: util.o helloworld.pb.o helloworld.grpc.pb.o greeter_callback_client.o
+	$(CXX) $^ $(LDFLAGS) -o $@
+
+greeter_callback_server: util.o helloworld.pb.o helloworld.grpc.pb.o greeter_callback_server.o
+	$(CXX) $^ $(LDFLAGS) -o $@
+
+.PRECIOUS: %.grpc.pb.cc
+%.grpc.pb.cc: %.proto
+	$(PROTOC) -I $(PROTOS_PATH) --grpc_out=. --plugin=protoc-gen-grpc=$(GRPC_CPP_PLUGIN_PATH) $<
+
+.PRECIOUS: %.pb.cc
+%.pb.cc: %.proto
+	$(PROTOC) -I $(PROTOS_PATH) --cpp_out=. $<
+
+util.o: ../util.cc
+	$(CXX) $^ -I . -I $(CPPFLAGS) -c -o $@
+
+clean:
+	rm -f *.o *.pb.cc *.pb.h greeter_callback_client greeter_callback_server
+
+
+# The following is to test your system and ensure a smoother experience.
+# They are by no means necessary to actually compile a grpc-enabled software.
+
+PROTOC_CMD = which $(PROTOC)
+PROTOC_CHECK_CMD = $(PROTOC) --version | grep -q 'libprotoc.3\|libprotoc [0-9][0-9]\.'
+PLUGIN_CHECK_CMD = which $(GRPC_CPP_PLUGIN)
+HAS_PROTOC = $(shell $(PROTOC_CMD) > /dev/null && echo true || echo false)
+ifeq ($(HAS_PROTOC),true)
+HAS_VALID_PROTOC = $(shell $(PROTOC_CHECK_CMD) 2> /dev/null && echo true || echo false)
+endif
+HAS_PLUGIN = $(shell $(PLUGIN_CHECK_CMD) > /dev/null && echo true || echo false)
+
+SYSTEM_OK = false
+ifeq ($(HAS_VALID_PROTOC),true)
+ifeq ($(HAS_PLUGIN),true)
+SYSTEM_OK = true
+endif
+endif
+
+system-check:
+ifneq ($(HAS_VALID_PROTOC),true)
+	@echo " DEPENDENCY ERROR"
+	@echo
+	@echo "You don't have protoc 3.0.0 or newer installed in your path."
+	@echo "Please install an up-to-date version of Google protocol buffers."
+	@echo "You can find it here:"
+	@echo
+	@echo "   https://github.com/protocolbuffers/protobuf/releases"
+	@echo
+	@echo "Here is what I get when trying to evaluate your version of protoc:"
+	@echo
+	-$(PROTOC) --version
+	@echo
+	@echo
+endif
+ifneq ($(HAS_PLUGIN),true)
+	@echo " DEPENDENCY ERROR"
+	@echo
+	@echo "You don't have the grpc c++ protobuf plugin installed in your path."
+	@echo "Please install grpc. You can find it here:"
+	@echo
+	@echo "   https://github.com/grpc/grpc"
+	@echo
+	@echo "Here is what I get when trying to detect if you have the plugin:"
+	@echo
+	-which $(GRPC_CPP_PLUGIN)
+	@echo
+	@echo
+endif
+ifneq ($(SYSTEM_OK),true)
+	@false
+endif

examples/cpp/otel/ostream/greeter_callback_client.cc

@@ -0,0 +1,79 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+// Explicitly define HAVE_ABSEIL to avoid conflict with OTel's Abseil
+// version. Refer
+// https://github.com/open-telemetry/opentelemetry-cpp/issues/1042.
+#ifndef HAVE_ABSEIL
+#define HAVE_ABSEIL
+#endif
+
+#include <string>
+
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "opentelemetry/exporters/ostream/metric_exporter.h"
+#include "opentelemetry/exporters/ostream/metric_exporter_factory.h"
+#include "opentelemetry/sdk/metrics/export/periodic_exporting_metric_reader.h"
+#include "opentelemetry/sdk/metrics/export/periodic_exporting_metric_reader_factory.h"
+#include "opentelemetry/sdk/metrics/meter_provider.h"
+
+#include <grpcpp/ext/otel_plugin.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/cpp/otel/util.h"
+#else
+#include "../util.h"
+#endif
+
+ABSL_FLAG(std::string, target, "localhost:50051", "Server address");
+
+int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
+  // Register a global gRPC OpenTelemetry plugin configured with an ostream
+  // exporter.
+  auto ostream_exporter =
+      opentelemetry::exporter::metrics::OStreamMetricExporterFactory::Create();
+  opentelemetry::sdk::metrics::PeriodicExportingMetricReaderOptions
+      reader_options;
+  reader_options.export_interval_millis = std::chrono::milliseconds(1000);
+  reader_options.export_timeout_millis = std::chrono::milliseconds(500);
+  auto reader =
+      opentelemetry::sdk::metrics::PeriodicExportingMetricReaderFactory::Create(
+          std::move(ostream_exporter), reader_options);
+  auto meter_provider =
+      std::make_shared<opentelemetry::sdk::metrics::MeterProvider>();
+  // The default histogram boundaries are not granular enough for RPCs. Override
+  // the "grpc.client.attempt.duration" view as recommended by
+  // https://github.com/grpc/proposal/blob/master/A66-otel-stats.md.
+  AddLatencyView(meter_provider.get(), "grpc.client.attempt.duration", "s");
+  meter_provider->AddMetricReader(std::move(reader));
+  auto status = grpc::OpenTelemetryPluginBuilder()
+                    .SetMeterProvider(std::move(meter_provider))
+                    .BuildAndRegisterGlobal();
+  if (!status.ok()) {
+    std::cerr << "Failed to register gRPC OpenTelemetry Plugin: "
+              << status.ToString() << std::endl;
+    return static_cast<int>(status.code());
+  }
+
+  // Continuously send RPCs every second.
+  RunClient(absl::GetFlag(FLAGS_target));
+
+  return 0;
+}

examples/cpp/otel/ostream/greeter_callback_server.cc

@@ -0,0 +1,78 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+// Explicitly define HAVE_ABSEIL to avoid conflict with OTel's Abseil
+// version. Refer
+// https://github.com/open-telemetry/opentelemetry-cpp/issues/1042.
+#ifndef HAVE_ABSEIL
+#define HAVE_ABSEIL
+#endif
+
+#include <iostream>
+#include <memory>
+#include <string>
+
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "opentelemetry/exporters/ostream/metric_exporter.h"
+#include "opentelemetry/exporters/ostream/metric_exporter_factory.h"
+#include "opentelemetry/sdk/metrics/export/periodic_exporting_metric_reader.h"
+#include "opentelemetry/sdk/metrics/export/periodic_exporting_metric_reader_factory.h"
+#include "opentelemetry/sdk/metrics/meter_provider.h"
+
+#include <grpcpp/ext/otel_plugin.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/cpp/otel/util.h"
+#else
+#include "../util.h"
+#endif
+
+ABSL_FLAG(uint16_t, port, 50051, "Server port for the service");
+
+int main(int argc, char** argv) {
+  absl::ParseCommandLine(argc, argv);
+  // Register a global gRPC OpenTelemetry plugin configured with an ostream
+  // exporter.
+  auto ostream_exporter =
+      opentelemetry::exporter::metrics::OStreamMetricExporterFactory::Create();
+  opentelemetry::sdk::metrics::PeriodicExportingMetricReaderOptions
+      reader_options;
+  reader_options.export_interval_millis = std::chrono::milliseconds(1000);
+  reader_options.export_timeout_millis = std::chrono::milliseconds(500);
+  auto reader =
+      opentelemetry::sdk::metrics::PeriodicExportingMetricReaderFactory::Create(
+          std::move(ostream_exporter), reader_options);
+  auto meter_provider =
+      std::make_shared<opentelemetry::sdk::metrics::MeterProvider>();
+  // The default histogram boundaries are not granular enough for RPCs. Override
+  // the "grpc.server.call.duration" view as recommended by
+  // https://github.com/grpc/proposal/blob/master/A66-otel-stats.md.
+  AddLatencyView(meter_provider.get(), "grpc.server.call.duration", "s");
+  meter_provider->AddMetricReader(std::move(reader));
+  auto status = grpc::OpenTelemetryPluginBuilder()
+                    .SetMeterProvider(std::move(meter_provider))
+                    .BuildAndRegisterGlobal();
+  if (!status.ok()) {
+    std::cerr << "Failed to register gRPC OpenTelemetry Plugin: "
+              << status.ToString() << std::endl;
+    return static_cast<int>(status.code());
+  }
+  RunServer(absl::GetFlag(FLAGS_port));
+  return 0;
+}

examples/cpp/otel/util.cc

@@ -16,17 +16,42 @@
 //
 //
 
-#ifdef BAZEL_BUILD
+// Explicitly define HAVE_ABSEIL to avoid conflict with OTel's Abseil
-#include "examples/cpp/otel/util.h"
+// version. Refer
-#else
+// https://github.com/open-telemetry/opentelemetry-cpp/issues/1042.
-#include "util.h"
+#ifndef HAVE_ABSEIL
+#define HAVE_ABSEIL
 #endif
 
+#include <condition_variable>
+#include <mutex>
+
 #include "opentelemetry/sdk/metrics/view/instrument_selector_factory.h"
 #include "opentelemetry/sdk/metrics/view/meter_selector_factory.h"
 #include "opentelemetry/sdk/metrics/view/view_factory.h"
 
+#include <grpcpp/ext/proto_server_reflection_plugin.h>
 #include <grpcpp/grpcpp.h>
+#include <grpcpp/health_check_service_interface.h>
+
+#ifdef BAZEL_BUILD
+#include "examples/cpp/otel/util.h"
+#include "examples/protos/helloworld.grpc.pb.h"
+#else
+#include "helloworld.grpc.pb.h"
+#include "util.h"
+#endif
+
+using grpc::CallbackServerContext;
+using grpc::Channel;
+using grpc::ClientContext;
+using grpc::Server;
+using grpc::ServerBuilder;
+using grpc::ServerUnaryReactor;
+using grpc::Status;
+using helloworld::Greeter;
+using helloworld::HelloReply;
+using helloworld::HelloRequest;
 
 void AddLatencyView(opentelemetry::sdk::metrics::MeterProvider* provider,
                     const std::string& name, const std::string& unit) {
@@ -48,3 +73,109 @@ void AddLatencyView(opentelemetry::sdk::metrics::MeterProvider* provider,
           opentelemetry::sdk::metrics::AggregationType::kHistogram,
           std::move(histogram_config)));
 }
+
+namespace {
+
+class GreeterClient {
+ public:
+  GreeterClient(std::shared_ptr<Channel> channel)
+      : stub_(Greeter::NewStub(channel)) {}
+
+  // Assembles the client's payload, sends it and presents the response back
+  // from the server.
+  std::string SayHello(const std::string& user) {
+    // Data we are sending to the server.
+    HelloRequest request;
+    request.set_name(user);
+
+    // Container for the data we expect from the server.
+    HelloReply reply;
+
+    // Context for the client. It could be used to convey extra information to
+    // the server and/or tweak certain RPC behaviors.
+    ClientContext context;
+
+    // The actual RPC.
+    std::mutex mu;
+    std::condition_variable cv;
+    bool done = false;
+    Status status;
+    stub_->async()->SayHello(&context, &request, &reply,
+                             [&mu, &cv, &done, &status](Status s) {
+                               status = std::move(s);
+                               std::lock_guard<std::mutex> lock(mu);
+                               done = true;
+                               cv.notify_one();
+                             });
+
+    std::unique_lock<std::mutex> lock(mu);
+    while (!done) {
+      cv.wait(lock);
+    }
+
+    // Act upon its status.
+    if (status.ok()) {
+      return reply.message();
+    } else {
+      std::cout << status.error_code() << ": " << status.error_message()
+                << std::endl;
+      return "RPC failed";
+    }
+  }
+
+ private:
+  std::unique_ptr<Greeter::Stub> stub_;
+};
+
+// Logic and data behind the server's behavior.
+class GreeterServiceImpl final : public Greeter::CallbackService {
+  ServerUnaryReactor* SayHello(CallbackServerContext* context,
+                               const HelloRequest* request,
+                               HelloReply* reply) override {
+    std::string prefix("Hello ");
+    reply->set_message(prefix + request->name());
+
+    ServerUnaryReactor* reactor = context->DefaultReactor();
+    reactor->Finish(Status::OK);
+    return reactor;
+  }
+};
+
+}  // namespace
+
+void RunServer(uint16_t port) {
+  std::string server_address = absl::StrFormat("0.0.0.0:%d", port);
+  GreeterServiceImpl service;
+
+  grpc::EnableDefaultHealthCheckService(true);
+  grpc::reflection::InitProtoReflectionServerBuilderPlugin();
+  ServerBuilder builder;
+  // Listen on the given address without any authentication mechanism.
+  builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
+  // Register "service" as the instance through which we'll communicate with
+  // clients. In this case it corresponds to an *synchronous* service.
+  builder.RegisterService(&service);
+  // Finally assemble the server.
+  std::unique_ptr<Server> server(builder.BuildAndStart());
+  std::cout << "Server listening on " << server_address << std::endl;
+
+  // Wait for the server to shutdown. Note that some other thread must be
+  // responsible for shutting down the server for this call to ever return.
+  server->Wait();
+}
+
+void RunClient(const std::string& target_str) {
+  // Instantiate the client. It requires a channel, out of which the actual RPCs
+  // are created. This channel models a connection to an endpoint specified by
+  // the argument "--target=" which is the only expected argument.
+  grpc::ChannelArguments args;
+  // Continuously send RPCs every second.
+  while (true) {
+    GreeterClient greeter(grpc::CreateCustomChannel(
+        target_str, grpc::InsecureChannelCredentials(), args));
+    std::string user("world");
+    std::string reply = greeter.SayHello(user);
+    std::cout << "Greeter received: " << reply << std::endl;
+    std::this_thread::sleep_for(std::chrono::seconds(1));
+  }
+}

examples/cpp/otel/util.h

@@ -28,4 +28,6 @@
 void AddLatencyView(opentelemetry::sdk::metrics::MeterProvider* provider,
                     const std::string& name, const std::string& unit);
 
+void RunServer(uint16_t port);
+void RunClient(const std::string& target_str);
 #endif  // GRPCPP_EXAMPLES_CPP_OTEL_UTIL_H

templates/CMakeLists.txt.template

@@ -119,7 +119,10 @@
       if lib_name == 'protobuf':
         # TODO(jtattermusch): add better way of excluding explicit protobuf dependency.
         continue
-      requires.add(lib_name)
+      if lib_name == 'opentelemetry-cpp::api':
+        requires.add('opentelemetry_api')
+      else:
+        requires.add(lib_name)
     return list(sorted(requires))
 
   def get_pkgconfig_requires_private(lib):
@@ -1142,3 +1145,14 @@
     "${" ".join(get_pkgconfig_libs("grpc++_unsecure"))}"
     "${" ".join(get_pkgconfig_libs_private("grpc++_unsecure"))}"
     "grpc++_unsecure.pc")
+
+  # grpcpp_otel_plugin .pc file
+  generate_pkgconfig(
+    "gRPC++ OpenTelemetry Plugin"
+    "OpenTelemetry Plugin for gRPC C++"
+    "<%text>${gRPC_CPP_VERSION}</%text>"
+    "${" ".join(get_pkgconfig_requires("grpcpp_otel_plugin"))}"
+    "${" ".join(get_pkgconfig_requires_private("grpcpp_otel_plugin"))}"
+    "${" ".join(get_pkgconfig_libs("grpcpp_otel_plugin"))}"
+    "${" ".join(get_pkgconfig_libs_private("grpcpp_otel_plugin"))}"
+    "grpcpp_otel_plugin.pc")

test/distrib/cpp/run_distrib_test_cmake_pkgconfig.sh

@@ -65,6 +65,13 @@ cmake -DCMAKE_BUILD_TYPE=Release ../..
 make "-j${GRPC_CPP_DISTRIBTEST_BUILD_COMPILER_JOBS}" install
 popd
 
+# Install OpenTelemetry
+mkdir -p "third_party/opentelemetry-cpp/cmake/build"
+pushd "third_party/opentelemetry-cpp/cmake/build"
+cmake -DCMAKE_BUILD_TYPE=Release -DWITH_ABSEIL=ON -DBUILD_TESTING=OFF -DWITH_BENCHMARK=OFF ../..
+make "-j${GRPC_CPP_DISTRIBTEST_BUILD_COMPILER_JOBS}" install
+popd
+
 # Just before installing gRPC, wipe out contents of all the submodules to simulate
 # a standalone build from an archive.
 # Get list of submodules from the .gitmodules file since for "git submodule foreach"
@@ -88,6 +95,7 @@ cmake \
   -DgRPC_RE2_PROVIDER=package \
   -DgRPC_SSL_PROVIDER=package \
   -DgRPC_ZLIB_PROVIDER=package \
+  -DgRPC_BUILD_GRPCPP_OTEL_PLUGIN=ON \
   ../..
 make "-j${GRPC_CPP_DISTRIBTEST_BUILD_COMPILER_JOBS}" install
 popd
@@ -111,3 +119,8 @@ popd
 pushd examples/cpp/route_guide
 make "-j${GRPC_CPP_DISTRIBTEST_BUILD_COMPILER_JOBS}"
 popd
+
+# Build otel example using Makefile and pkg-config
+pushd examples/cpp/otel/ostream
+make "-j${GRPC_CPP_DISTRIBTEST_BUILD_COMPILER_JOBS}"
+popd