Github user zuyu commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/232#discussion_r112547224
--- Diff: cli/NetworkIO.hpp ---
@@ -0,0 +1,227 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 QUICKSTEP_CLI_NETWORK_IO_HPP_
+#define QUICKSTEP_CLI_NETWORK_IO_HPP_
+
+#include <grpc++/grpc++.h>
+
+#include <iostream>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "cli/Flags.hpp"
+#include "cli/IOInterface.hpp"
+#include "cli/NetworkCli.grpc.pb.h"
+#include "cli/NetworkCli.pb.h"
+#include "threading/ConditionVariable.hpp"
+#include "threading/Mutex.hpp"
+#include "utility/MemStream.hpp"
+
+#include "gflags/gflags.h"
+#include "glog/logging.h"
+
+using grpc::Channel;
+using grpc::ClientContext;
+using grpc::Server;
+using grpc::Status;
+
+namespace quickstep {
+
+namespace networkio_internal {
+
+/**
+ * Contains state and helper methods for managing interactions between a
producer/consumer (requestor/requestee)
+ * thread.
+ */
+class RequestState {
+ public:
+ RequestState() :
+ request_ready_(false),
+ response_ready_(false),
+ request_buffer_(""),
+ mutex_(),
+ condition_() {}
+
+ /**
+ * Notifies waiter that a piece of work has been created and added to
the buffer.
+ * @param to_consume The arguments for the consuming thread.
+ */
+ void requestReady(std::string to_consume) {
+ request_ready_ = true;
+ response_ready_ = false;
+ request_buffer_ = to_consume;
+ condition_.notify_one();
+ }
+
+ /**
+ * Notifies that the consumer has finished consuming and that a response
is ready.
+ * To be called after the consumer has executed.
+ */
+ void responseReady() {
+ request_ready_ = false;
+ response_ready_ = true;
+ condition_.notify_one();
+ }
+
+ bool request_ready_;
+ bool response_ready_;
+ std::string request_buffer_;
+ QueryResponse response_message_;
+ std::mutex mutex_;
+ std::condition_variable condition_;
+};
+} // namespace networkio_internal
+
+class NetworkCliServiceImpl final : public NetworkCli::Service {
+ public:
+ NetworkCliServiceImpl()
+ : NetworkCli::Service(),
+ worker_exclusive_mtx_(),
+ running_(true),
+ request_state_() { }
+
+ /**
+ * Handles gRPC request. Sets the buffer in the RequestState, notifies
the main thread, then waits for a response.
+ * @param context
+ * @param request
+ * @param response
+ * @return
+ */
+ Status SendQuery(grpc::ServerContext *context,
+ const QueryRequest *request,
+ QueryResponse *response) override {
+ auto service_ex_lock = enter();
+ if (!service_ex_lock) {
+ return Status::CANCELLED;
+ }
+
+ // Service thread sets a notification for the main thread.
+ // Because of service thread exclusivity, we have rights to this data
structure.
+ request_state_.requestReady(request->query());
+
+ // Service thread - main thread critical section:
+ // Service thread waits for the buffered message response from the
main thread. The main thread will set
+ // consumer_ready_ when it is finished and released its exclusive lock
on the communication data structure.
+ std::unique_lock<std::mutex> lock(request_state_.mutex_);
+ while (!request_state_.response_ready_)
+ request_state_.condition_.wait(lock);
+
+ *response = request_state_.response_message_;
+
+ return Status::OK;
+ }
+
+ void kill() {
+ running_ = false;
+ }
+
+ networkio_internal::RequestState& getRequestState() {
+ return request_state_;
+ }
+
+ private:
+ /**
+ * When a worker enters, it gains exclusive access to the main thread.
That is, no other worker of this service
+ * is allowed to interact with main thread.
+ * @return A lock which grants the worker mutual exclusion.
+ */
+ std::unique_lock<std::mutex> enter() {
+ std::unique_lock<std::mutex> lock(worker_exclusive_mtx_);
+ if (!running_)
+ lock.unlock();
+ return lock;
+ }
+
+ std::mutex worker_exclusive_mtx_;
+ bool running_;
+ networkio_internal::RequestState request_state_;
+};
+
+class NetworkIO : public IOInterface {
+ public:
+ NetworkIO()
+ : IOInterface(),
+ out_stream_(),
+ err_stream_(),
+ server_(nullptr),
+ service_() {
+ std::string server_address("0.0.0.0:" + std::to_string(FLAGS_port));
+
+ // Starts a server.
+ grpc::ServerBuilder builder;
+ builder.AddListeningPort(server_address,
grpc::InsecureServerCredentials());
+ builder.RegisterService(&service_);
+ server_ = builder.BuildAndStart();
+ LOG(INFO) << "Listening on port " << std::to_string(FLAGS_port);
+ }
+
+ FILE* out() override {
+ return out_stream_.file();
+ }
+
+ FILE* err() override {
+ return err_stream_.file();
+ }
+
+ std::string getNextCommand() override {
+ // critical section: wait for a command
+ networkio_internal::RequestState& request_state =
service_.getRequestState();
--- End diff --
Change to `networkio_internal::RequestState &request_state`.
Ditto in `notifyCommandComplete`.
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