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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include "monitoring/histogram.h"
namespace ROCKSDB_NAMESPACE {
class SystemClock;
class HistogramWindowingImpl : public Histogram {
public:
HistogramWindowingImpl();
HistogramWindowingImpl(uint64_t num_windows, uint64_t micros_per_window,
uint64_t min_num_per_window);
HistogramWindowingImpl(const HistogramWindowingImpl&) = delete;
HistogramWindowingImpl& operator=(const HistogramWindowingImpl&) = delete;
~HistogramWindowingImpl();
virtual void Clear() override;
virtual bool Empty() const override;
virtual void Add(uint64_t value) override;
virtual void Merge(const Histogram& other) override;
void Merge(const HistogramWindowingImpl& other);
virtual std::string ToString() const override;
virtual const char* Name() const override { return "HistogramWindowingImpl"; }
virtual uint64_t min() const override { return stats_.min(); }
virtual uint64_t max() const override { return stats_.max(); }
virtual uint64_t num() const override { return stats_.num(); }
virtual double Median() const override;
virtual double Percentile(double p) const override;
virtual double Average() const override;
virtual double StandardDeviation() const override;
virtual void Data(HistogramData* const data) const override;
#ifndef NDEBUG
void TEST_UpdateClock(const std::shared_ptr<SystemClock>& clock) {
clock_ = clock;
}
#endif // NDEBUG
private:
void TimerTick();
void SwapHistoryBucket();
inline uint64_t current_window() const {
return current_window_.load(std::memory_order_relaxed);
}
inline uint64_t last_swap_time() const {
return last_swap_time_.load(std::memory_order_relaxed);
}
std::shared_ptr<SystemClock> clock_;
std::mutex mutex_;
// Aggregated stats over windows_stats_, all the computation is done
// upon aggregated values
HistogramStat stats_;
// This is a circular array representing the latest N time-windows.
// Each entry stores a time-window of data. Expiration is done
// on window-based.
std::unique_ptr<HistogramStat[]> window_stats_;
std::atomic_uint_fast64_t current_window_;
std::atomic_uint_fast64_t last_swap_time_;
// Following parameters are configuable
uint64_t num_windows_ = 5;
uint64_t micros_per_window_ = 60000000;
// By default, don't care about the number of values in current window
// when decide whether to swap windows or not.
uint64_t min_num_per_window_ = 0;
};
} // namespace ROCKSDB_NAMESPACE
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