batch_queue.h

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/*
 * 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.
 */
 
#pragma once
 
#include <glog/logging.h>
 
#include <condition_variable>
#include <list>
 
namespace resdb {
 
template <typename T>
class BatchQueue {
  struct BatchQueueItem {
    std::vector<T> list;
  };
 
 public:
  int num = 0;
  BatchQueue() = default;
  BatchQueue(const std::string& name, int batch_size)
      : name_(name), batch_size_(batch_size) {}
  void Push(T&& data) {
    std::lock_guard<std::mutex> lk(mutex_);
    if (queue_.empty() || queue_.back()->list.size() >= batch_size_) {
      queue_.push_back(std::make_unique<BatchQueueItem>());
      queue_.back()->list.reserve(batch_size_);
    }
    queue_.back()->list.push_back(std::move(data));
    cv_.notify_all();
  }
 
  size_t Size() { return queue_.size(); }
 
  std::vector<T> Pop(int timeout_ms) {
    std::unique_ptr<BatchQueueItem> item = nullptr;
    {
      std::unique_lock<std::mutex> lk(mutex_);
      if (timeout_ms > 0) {
        cv_.wait_for(lk, std::chrono::microseconds(timeout_ms), [&] {
          return !queue_.empty() && queue_.front()->list.size() >= batch_size_;
        });
      }
      if (queue_.empty()) {
        return std::vector<T>();
      }
      item = std::move(queue_.front());
      queue_.pop_front();
    }
    return std::move(item->list);
  }
 
 private:
  std::string name_;
  std::condition_variable cv_;
  std::mutex mutex_;
  //  std::queue<T> queue_ GUARDED_BY(mutex_);
  std::list<std::unique_ptr<BatchQueueItem>> queue_;
  size_t batch_size_;
};
 
}  // namespace resdb