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1 介绍

详见：https://grpc.io/docs/

2 示例

2.1 项目结构

grpc
├── helloworld
│   ├── BUILD
│   ├── greeter_client.cc
│   ├── greeter_server.cc
│   └── proto
│       ├── BUILD
│       └── helloworld.proto
└── WORKSPACE

2.2 源码

• helloworld/proto/helloworld.proto：定义要传输的消息

  // 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.
  
  syntax = "proto3";
  
  package helloworld;
  
  // The greeting service definition.
  service Greeter {
    // Sends a greeting
    rpc SayHello (HelloRequest) returns (HelloReply) {}
  }
  
  // The request message containing the user's name.
  message HelloRequest {
    string name = 1;
  }
  
  // The response message containing the greetings
  message HelloReply {
    string message = 1;
  }

• helloworld/proto/BUILD：生成 c++ 格式的头文件

  # Copyright 2020 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.
  
  package(default_visibility = ["//visibility:public"])
  
  load("@rules_proto//proto:defs.bzl", "proto_library")
  load("@com_github_grpc_grpc//bazel:cc_grpc_library.bzl", "cc_grpc_library")
  load("@com_github_grpc_grpc//bazel:grpc_build_system.bzl", "grpc_proto_library")
  
  # The following three rules demonstrate the usage of the cc_grpc_library rule in
  # in a mode compatible with the native proto_library and cc_proto_library rules.
  proto_library(
      name = "helloworld_proto",
      srcs = ["helloworld.proto"],
  )
  
  cc_proto_library(
      name = "helloworld_cc_proto",
      deps = [":helloworld_proto"],
  )
  
  cc_grpc_library(
      name = "helloworld_cc_grpc",
      srcs = [":helloworld_proto"],
      deps = [":helloworld_cc_proto"],
      grpc_only = True,
  )

• helloword/greeter_server.cc

  /*
   *
   * 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.
   *
   */
  
  #include <iostream>
  #include <memory>
  #include <string>
  
  #include <grpcpp/grpcpp.h>
  #include <grpcpp/health_check_service_interface.h>
  
  #include "helloworld/proto/helloworld.grpc.pb.h"
  
  using grpc::Server;
  using grpc::ServerBuilder;
  using grpc::ServerContext;
  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::Service {
    Status SayHello(ServerContext* context,
                    const HelloRequest* request,
                    HelloReply* reply) override {
      std::string prefix("Hello ");
      reply->set_message(prefix + request->name());
      return Status::OK;
    }
  };
  
  void RunServer() {
    std::string server_address("0.0.0.0:50051");
    GreeterServiceImpl service;
  
    grpc::EnableDefaultHealthCheckService(true);
    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) {
    RunServer();
  
    return 0;
  }

• helloword/greeter_client.cc

  /*
   *
   * 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.
   *
   */
  
  #include <iostream>
  #include <memory>
  #include <string>
  
  #include <grpcpp/grpcpp.h>
  
  #include "helloworld/proto/helloworld.grpc.pb.h"
  
  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.
      Status status = stub_->SayHello(&context, request, &reply);
  
      // 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) {
    // 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.
    // We indicate that the channel isn't authenticated (use of
    // InsecureChannelCredentials()).
    std::string target_str = "localhost:50051";
  
    GreeterClient greeter(
        grpc::CreateChannel(target_str, grpc::InsecureChannelCredentials()));
    std::string user("world");
    std::string reply = greeter.SayHello(user);
    std::cout << "Greeter received: " << reply << std::endl;
  
    return 0;
  }

• helloword/BUILD

  # Copyright 2020 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.
  
  package(default_visibility = ["//visibility:public"])
  
  load("@rules_cc//cc:defs.bzl", "cc_proto_library")
  load("@rules_proto//proto:defs.bzl", "proto_library")
  
  cc_binary(
      name = "greeter-client",
      srcs = ["greeter_client.cc"],
      deps = [
          "@com_github_grpc_grpc//:grpc++",
          "//helloworld/proto:helloworld_cc_grpc",
      ],
  )
  
  cc_binary(
      name = "greeter-server",
      srcs = ["greeter_server.cc"],
      deps = [
          "@com_github_grpc_grpc//:grpc++",
          "//helloworld/proto:helloworld_cc_grpc",
      ],
  )

• WORKSPACE：下载相关依赖

  workspace(name = "example")
  
  load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
  
  http_archive(
      name = "rules_proto",
      sha256 = "602e7161d9195e50246177e7c55b2f39950a9cf7366f74ed5f22fd45750cd208",
      strip_prefix = "rules_proto-97d8af4dc474595af3900dd85cb3a29ad28cc313",
      urls = [
          "https://mirror.bazel.build/github.com/bazelbuild/rules_proto/archive/97d8af4dc474595af3900dd85cb3a29ad28cc313.tar.gz",
          "https://github.com/bazelbuild/rules_proto/archive/97d8af4dc474595af3900dd85cb3a29ad28cc313.tar.gz",
      ],
  )
  load("@rules_proto//proto:repositories.bzl", "rules_proto_dependencies", "rules_proto_toolchains")
  rules_proto_dependencies()
  rules_proto_toolchains()
  
  
  http_archive(
      name = "com_google_protobuf",
      strip_prefix = "protobuf-3.10.1",
      sha256 = "d7cfd31620a352b2ee8c1ed883222a0d77e44346643458e062e86b1d069ace3e",
      urls = [
          "https://release.mad.st.meituan.com/bazel/deps/protobuf-all-3.10.1.tar.gz",
          "https://release.mad.st.sankuai.com/bazel/deps/protobuf-all-3.10.1.tar.gz"
      ]
  )
  
  http_archive(
      name = "com_github_grpc_grpc",
      sha256 = "393d5abc343db59b4d27b18819718bcd61f9c313f2ada35fb63992780d09d693",
      strip_prefix = "grpc-1.28.1",
      urls = [
          "https://release.mad.st.meituan.com/bazel/deps/grpc_deps/grpc-1.28.1-v1.tar.gz",
          "https://release.mad.st.sankuai.com/bazel/deps/grpc_deps/grpc-1.28.1-v1.tar.gz",
      ],
  )
  
  load("@com_github_grpc_grpc//bazel:grpc_deps.bzl", "grpc_deps")
  grpc_deps()
  
  load("@com_github_grpc_grpc//bazel:grpc_extra_deps.bzl", "grpc_extra_deps")
  grpc_extra_deps()

2.3 运行结果

服务端：

$ ./bazel-bin/helloworld/greeter-server
Server listening on 0.0.0.0:50051

客户端：

$ ./bazel-bin/helloworld/greeter-client
Greeter received: Hello world