async_grpc_client.hpp

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#ifndef IROHA_ASYNC_GRPC_CLIENT_HPP
#define IROHA_ASYNC_GRPC_CLIENT_HPP

#include <ciso646>
#include <thread>

#include <google/protobuf/empty.pb.h>
#include <grpc++/grpc++.h>
#include <grpcpp/impl/codegen/async_unary_call.h>
#include "logger/logger.hpp"

namespace iroha {
  namespace network {

    template <typename Response>
    class AsyncGrpcClient {
     public:
      explicit AsyncGrpcClient(logger::LoggerPtr log)
          : thread_(&AsyncGrpcClient::asyncCompleteRpc, this),
            log_(std::move(log)) {}

      void asyncCompleteRpc() {
        void *got_tag;
        auto ok = false;
        while (cq_.Next(&got_tag, &ok)) {
          auto call = static_cast<AsyncClientCall *>(got_tag);
          if (not call->status.ok()) {
            log_->warn("RPC failed: {}", call->status.error_message());
          }
          if (call->on_response) {
            call->on_response(call->status, call->reply);
          }
          delete call;
        }
      }

      ~AsyncGrpcClient() {
        cq_.Shutdown();
        if (thread_.joinable()) {
          thread_.join();
        }
      }

      grpc::CompletionQueue cq_;
      std::thread thread_;

      struct AsyncClientCall {
        Response reply;

        grpc::ClientContext context;

        grpc::Status status;

        std::unique_ptr<grpc::ClientAsyncResponseReaderInterface<Response>>
            response_reader;

        std::function<void(grpc::Status &, Response &)> on_response;
      };

      template <typename F>
      void Call(
          F &&lambda,
          std::function<void(grpc::Status &, Response &)> on_response = {}) {
        auto call = new AsyncClientCall;
        call->on_response = std::move(on_response);
        call->response_reader = lambda(&call->context, &cq_);
        call->response_reader->Finish(&call->reply, &call->status, call);
      }

     private:
      logger::LoggerPtr log_;
    };
  }  // namespace network
}  // namespace iroha

#endif  // IROHA_ASYNC_GRPC_CLIENT_HPP