Codel.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 <atomic>
#include <chrono>

#include <folly/portability/GFlags.h>

DECLARE_int32(codel_interval);
DECLARE_int32(codel_target_delay);

namespace folly {

class Codel {
 public:
  Codel();

  bool overloaded(std::chrono::nanoseconds delay);

  int getLoad();

  std::chrono::nanoseconds getMinDelay();
  std::chrono::milliseconds getInterval();
  std::chrono::milliseconds getTargetDelay();
  std::chrono::milliseconds getSloughTimeout();

 private:
  std::atomic<uint64_t> codelMinDelayNs_;
  std::atomic<uint64_t> codelIntervalTimeNs_;

  // flag to make overloaded() thread-safe, since we only want
  // to reset the delay once per time period
  std::atomic<bool> codelResetDelay_;

  std::atomic<bool> overloaded_;
};

} // namespace folly