szaszm commented on a change in pull request #746: MINIFICPP-1185 - Remove moodycamel::concurrentqueue from threadpool URL: https://github.com/apache/nifi-minifi-cpp/pull/746#discussion_r400057782
########## File path: libminifi/include/utils/MinifiConcurrentQueue.h ########## @@ -0,0 +1,186 @@ +/** + * 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 LIBMINIFI_INCLUDE_CONCURRENT_QUEUE_H +#define LIBMINIFI_INCLUDE_CONCURRENT_QUEUE_H + +#include <chrono> +#include <deque> +#include <mutex> +#include <condition_variable> +#include <stdexcept> + +namespace org { +namespace apache { +namespace nifi { +namespace minifi { +namespace utils { + + +// Provides a queue API and guarantees no race conditions in case of multiple producers and consumers. +template <typename T> +class ConcurrentQueue { + public: + explicit ConcurrentQueue() = default; + + ConcurrentQueue(const ConcurrentQueue& other) = delete; + ConcurrentQueue& operator=(const ConcurrentQueue& other) = delete; + ConcurrentQueue(ConcurrentQueue&& other) + : ConcurrentQueue(std::move(other), std::lock_guard<std::mutex>(other.mutex_)) {} + + ConcurrentQueue& operator=(ConcurrentQueue&& other) { + if (this != &other) { + std::lock(mtx_, other.mtx_); + std::lock_guard<std::mutex> lk1(mtx_, std::adopt_lock); + std::lock_guard<std::mutex> lk2(other.mtx_, std::adopt_lock); + queue_.swap(other.queue_); + } + return *this; + } + + bool tryDequeue(T& out) { + std::unique_lock<std::mutex> lck(mtx_); + return tryDequeueImpl(lck, out); + } + + bool empty() const { + std::unique_lock<std::mutex> lck(mtx_); + return queue_.emptyImpl(lck); + } + + size_t size() const { + std::lock_guard<std::mutex> guard(mtx_); + return queue_.size(); + } + + void clear() { + std::lock_guard<std::mutex> guard(mtx_); + queue_.clear(); + } + + template <typename... Args> + void enqueue(Args&&... args) { + std::lock_guard<std::mutex> guard(mtx_); + queue_.emplace_back(std::forward<Args>(args)...); + } + + private: + ConcurrentQueue(ConcurrentQueue&& other, std::lock_guard<std::mutex>&) + : queue_( std::move(other.queue_) ) {} + + protected: + void checkLock(std::unique_lock<std::mutex>& lck) const { + if (!lck.owns_lock()) { + throw std::logic_error("Caller of protected functions of ConcurrentQueue should own the lock!"); + } + } + + bool tryDequeueImpl(std::unique_lock<std::mutex>& lck, T& out) { + checkLock(lck); + if (queue_.empty()) { + return false; + } + out = std::move(queue_.front()); + queue_.pop_front(); + return true; + } + + bool emptyImpl(std::unique_lock<std::mutex>& lck) const { + checkLock(lck); + return queue_.empty(); + } + + mutable std::mutex mtx_; + private: + std::deque<T> queue_; +}; + + +// A ConcurrentQueue extended with a condition variable to be able to block and wait for incoming data +template <typename T> +class ConditionConcurrentQueue : private ConcurrentQueue<T> { + public: + explicit ConditionConcurrentQueue(bool start = true) : ConcurrentQueue<T>{}, running_{start} {} + + ConditionConcurrentQueue(const ConditionConcurrentQueue& other) = delete; + ConditionConcurrentQueue& operator=(const ConditionConcurrentQueue& other) = delete; + ConditionConcurrentQueue(ConditionConcurrentQueue&& other) = delete; + ConditionConcurrentQueue& operator=(ConditionConcurrentQueue&& other) = delete; + + using ConcurrentQueue<T>::size; + using ConcurrentQueue<T>::empty; + using ConcurrentQueue<T>::clear; + + + template <typename... Args> + void enqueue(Args&&... args) { + ConcurrentQueue<T>::enqueue(std::forward<Args>(args)...); + if (running_) { + cv_.notify_one(); + } + } + + bool dequeueWait(T& out) { + std::unique_lock<std::mutex> lck(this->mtx_); + cv_.wait(lck, [this, &lck]{ return !running_ || !this->emptyImpl(lck); }); // Only wake up if there is something to return or stopped + return running_ && ConcurrentQueue<T>::tryDequeueImpl(lck, out); + } + + template< class Rep, class Period > + bool dequeueWaitFor(T& out, const std::chrono::duration<Rep, Period>& time) { + std::unique_lock<std::mutex> lck(this->mtx_); + cv_.wait_for(lck, time, [this, &lck]{ return !running_ || !this->emptyImpl(lck); }); // Wake up with timeout or in case there is something to do + return running_ && ConcurrentQueue<T>::tryDequeueImpl(lck, out); + } + + bool tryDequeue(T& out) { + std::unique_lock<std::mutex> lck(this->mtx_); + return running_ && ConcurrentQueue<T>::tryDequeueImpl(lck, out); + } + + void stop() { + std::lock_guard<std::mutex> guard(this->mtx_); + running_ = false; + cv_.notify_all(); + } + + void start() { + std::unique_lock<std::mutex> lck(this->mtx_); + if (!running_) { + running_ = true; + if (!this->emptyImpl(lck)) { + cv_.notify_all(); + } Review comment: Since we are transitioning from stopped to started in a critical section, and it's not possible to have consumers in a stopped state, this notification shouldn't be necessary. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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