ceph/src/rocksdb/monitoring/histogram_windowing.h

   1 //  Copyright (c) 2013, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under the BSD-style license found in the
   3 //  LICENSE file in the root directory of this source tree. An additional grant
   4 //  of patent rights can be found in the PATENTS file in the same directory.
   5 //
   6 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
   7 // Use of this source code is governed by a BSD-style license that can be
   8 // found in the LICENSE file. See the AUTHORS file for names of contributors.
   9
  10 #pragma once
  11
  12 #include "monitoring/histogram.h"
  13 #include "rocksdb/env.h"
  14
  15 namespace rocksdb {
  16
  17 class HistogramWindowingImpl : public Histogram
  18 {
  19 public:
  20   HistogramWindowingImpl();
  21   HistogramWindowingImpl(uint64_t num_windows,
  22                          uint64_t micros_per_window,
  23                          uint64_t min_num_per_window);
  24
  25   HistogramWindowingImpl(const HistogramImpl&) = delete;
  26   HistogramWindowingImpl& operator=(const HistogramImpl&) = delete;
  27
  28   ~HistogramWindowingImpl();
  29
  30   virtual void Clear() override;
  31   virtual bool Empty() const override;
  32   virtual void Add(uint64_t value) override;
  33   virtual void Merge(const Histogram& other) override;
  34   void Merge(const HistogramWindowingImpl& other);
  35
  36   virtual std::string ToString() const override;
  37   virtual const char* Name() const override { return "HistogramWindowingImpl"; }
  38   virtual uint64_t min() const override { return stats_.min(); }
  39   virtual uint64_t max() const override { return stats_.max(); }
  40   virtual uint64_t num() const override { return stats_.num(); }
  41   virtual double Median() const override;
  42   virtual double Percentile(double p) const override;
  43   virtual double Average() const override;
  44   virtual double StandardDeviation() const override;
  45   virtual void Data(HistogramData* const data) const override;
  46
  47 private:
  48   void TimerTick();
  49   void SwapHistoryBucket();
  50   inline uint64_t current_window() const {
  51     return current_window_.load(std::memory_order_relaxed);
  52   }
  53   inline uint64_t last_swap_time() const{
  54     return last_swap_time_.load(std::memory_order_relaxed);
  55   }
  56
  57   Env* env_;
  58   std::mutex mutex_;
  59
  60   // Aggregated stats over windows_stats_, all the computation is done
  61   // upon aggregated values
  62   HistogramStat stats_;
  63
  64   // This is a circular array representing the latest N time-windows.
  65   // Each entry stores a time-window of data. Expiration is done
  66   // on window-based.
  67   std::unique_ptr<HistogramStat[]> window_stats_;
  68
  69   std::atomic_uint_fast64_t current_window_;
  70   std::atomic_uint_fast64_t last_swap_time_;
  71
  72   // Following parameters are configuable
  73   uint64_t num_windows_ = 5;
  74   uint64_t micros_per_window_ = 60000000;
  75   // By default, don't care about the number of values in current window
  76   // when decide whether to swap windows or not.
  77   uint64_t min_num_per_window_ = 0;
  78 };
  79
  80 }  // namespace rocksdb