CPUThreadPoolExecutor.h

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/*
 * Copyright 2017-present Facebook, Inc.
 *
 * 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.
 */

#pragma once

#include <folly/executors/ThreadPoolExecutor.h>

DECLARE_bool(dynamic_cputhreadpoolexecutor);

namespace folly {

class CPUThreadPoolExecutor : public ThreadPoolExecutor {
 public:
  struct CPUTask;

  CPUThreadPoolExecutor(
      size_t numThreads,
      std::unique_ptr<BlockingQueue<CPUTask>> taskQueue,
      std::shared_ptr<ThreadFactory> threadFactory =
          std::make_shared<NamedThreadFactory>("CPUThreadPool"));

  CPUThreadPoolExecutor(
      std::pair<size_t, size_t> numThreads,
      std::unique_ptr<BlockingQueue<CPUTask>> taskQueue,
      std::shared_ptr<ThreadFactory> threadFactory =
          std::make_shared<NamedThreadFactory>("CPUThreadPool"));

  explicit CPUThreadPoolExecutor(size_t numThreads);

  CPUThreadPoolExecutor(
      size_t numThreads,
      std::shared_ptr<ThreadFactory> threadFactory);

  CPUThreadPoolExecutor(
      std::pair<size_t, size_t> numThreads,
      std::shared_ptr<ThreadFactory> threadFactory);

  CPUThreadPoolExecutor(
      size_t numThreads,
      int8_t numPriorities,
      std::shared_ptr<ThreadFactory> threadFactory =
          std::make_shared<NamedThreadFactory>("CPUThreadPool"));

  CPUThreadPoolExecutor(
      size_t numThreads,
      int8_t numPriorities,
      size_t maxQueueSize,
      std::shared_ptr<ThreadFactory> threadFactory =
          std::make_shared<NamedThreadFactory>("CPUThreadPool"));

  ~CPUThreadPoolExecutor() override;

  void add(Func func) override;
  void add(
      Func func,
      std::chrono::milliseconds expiration,
      Func expireCallback = nullptr) override;

  void addWithPriority(Func func, int8_t priority) override;
  void add(
      Func func,
      int8_t priority,
      std::chrono::milliseconds expiration,
      Func expireCallback = nullptr);

  size_t getTaskQueueSize() const;

  uint8_t getNumPriorities() const override;

  struct CPUTask : public ThreadPoolExecutor::Task {
    // Must be noexcept move constructible so it can be used in MPMCQueue

    explicit CPUTask(
        Func&& f,
        std::chrono::milliseconds expiration,
        Func&& expireCallback)
        : Task(std::move(f), expiration, std::move(expireCallback)),
          poison(false) {}
    CPUTask()
        : Task(nullptr, std::chrono::milliseconds(0), nullptr), poison(true) {}

    bool poison;
  };

  static const size_t kDefaultMaxQueueSize;

 protected:
  BlockingQueue<CPUTask>* getTaskQueue();

 private:
  void threadRun(ThreadPtr thread) override;
  void stopThreads(size_t n) override;
  size_t getPendingTaskCountImpl() override;

  bool tryDecrToStop();
  bool taskShouldStop(folly::Optional<CPUTask>&);

  std::unique_ptr<BlockingQueue<CPUTask>> taskQueue_;
  std::atomic<ssize_t> threadsToStop_{0};
};

} // namespace folly