examples/cpp/interceptors/server.cc

/*
 *
 * 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.
 *
 */

#include <iostream>
#include <memory>
#include <string>
#include <vector>

#include <grpcpp/grpcpp.h>
#include <grpcpp/support/server_interceptor.h>

#ifdef BAZEL_BUILD
#include "examples/protos/keyvaluestore.grpc.pb.h"
#else
#include "keyvaluestore.grpc.pb.h"
#endif

using grpc::CallbackServerContext;
using grpc::Server;
using grpc::ServerBidiReactor;
using grpc::ServerBuilder;
using grpc::Status;
using grpc::experimental::InterceptionHookPoints;
using grpc::experimental::Interceptor;
using grpc::experimental::InterceptorBatchMethods;
using grpc::experimental::ServerInterceptorFactoryInterface;
using grpc::experimental::ServerRpcInfo;
using keyvaluestore::KeyValueStore;
using keyvaluestore::Request;
using keyvaluestore::Response;

// This is a simple interceptor that logs whenever it gets a request, which on
// the server side happens when initial metadata is received.
class LoggingInterceptor : public Interceptor {
 public:
  void Intercept(InterceptorBatchMethods* methods) override {
    if (methods->QueryInterceptionHookPoint(
            InterceptionHookPoints::POST_RECV_INITIAL_METADATA)) {
      std::cout << "Got a new streaming RPC" << std::endl;
    }
    methods->Proceed();
  }
};

class LoggingInterceptorFactory : public ServerInterceptorFactoryInterface {
 public:
  Interceptor* CreateServerInterceptor(ServerRpcInfo* info) override {
    return new LoggingInterceptor();
  }
};

struct kv_pair {
  const char* key;
  const char* value;
};

static const kv_pair kvs_map[] = {
    {"key1", "value1"}, {"key2", "value2"}, {"key3", "value3"},
    {"key4", "value4"}, {"key5", "value5"},
};

const char* get_value_from_map(const char* key) {
  for (size_t i = 0; i < sizeof(kvs_map) / sizeof(kv_pair); ++i) {
    if (strcmp(key, kvs_map[i].key) == 0) {
      return kvs_map[i].value;
    }
  }
  return "";
}

// Logic behind the server's behavior.
class KeyValueStoreServiceImpl final : public KeyValueStore::CallbackService {
  ServerBidiReactor<Request, Response>* GetValues(
      CallbackServerContext* context) override {
    class Reactor : public ServerBidiReactor<Request, Response> {
     public:
      explicit Reactor() { StartRead(&request_); }

      void OnReadDone(bool ok) override {
        if (!ok) {
          return Finish(grpc::Status::CANCELLED);
        }
        response_.set_value(get_value_from_map(request_.key().c_str()));
        StartWrite(&response_);
      }

      void OnWriteDone(bool ok) override {
        if (!ok) {
          return Finish(grpc::Status::CANCELLED);
        }
        StartRead(&request_);
      }

      void OnDone() override { delete this; }

     private:
      Request request_;
      Response response_;
    };

    return new Reactor();
  }
};

void RunServer() {
  std::string server_address("0.0.0.0:50051");
  KeyValueStoreServiceImpl service;

  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);
  std::vector<std::unique_ptr<ServerInterceptorFactoryInterface>> creators;
  creators.push_back(std::unique_ptr<ServerInterceptorFactoryInterface>(
      new LoggingInterceptorFactory()));
  builder.experimental().SetInterceptorCreators(std::move(creators));
  // 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;
}