go.temporal.io/server@v1.23.0/common/aggregate/moving_window_average.go (about)

     1  // The MIT License
     2  //
     3  // Copyright (c) 2020 Temporal Technologies Inc.  All rights reserved.
     4  //
     5  // Copyright (c) 2020 Uber Technologies, Inc.
     6  //
     7  // Permission is hereby granted, free of charge, to any person obtaining a copy
     8  // of this software and associated documentation files (the "Software"), to deal
     9  // in the Software without restriction, including without limitation the rights
    10  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    11  // copies of the Software, and to permit persons to whom the Software is
    12  // furnished to do so, subject to the following conditions:
    13  //
    14  // The above copyright notice and this permission notice shall be included in
    15  // all copies or substantial portions of the Software.
    16  //
    17  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    18  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    19  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    20  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    21  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    22  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    23  // THE SOFTWARE.
    24  
    25  package aggregate
    26  
    27  import (
    28  	"sync"
    29  	"time"
    30  )
    31  
    32  type (
    33  	MovingWindowAverage interface {
    34  		Record(val int64)
    35  		Average() float64
    36  	}
    37  
    38  	timestampedData struct {
    39  		value     int64
    40  		timestamp time.Time
    41  	}
    42  
    43  	MovingWindowAvgImpl struct {
    44  		sync.Mutex
    45  		windowSize    time.Duration
    46  		maxBufferSize int
    47  		buffer        []timestampedData
    48  		headIdx       int
    49  		tailIdx       int
    50  		sum           int64
    51  		count         int64
    52  	}
    53  )
    54  
    55  func NewMovingWindowAvgImpl(
    56  	windowSize time.Duration,
    57  	maxBufferSize int,
    58  ) *MovingWindowAvgImpl {
    59  	return &MovingWindowAvgImpl{
    60  		windowSize:    windowSize,
    61  		maxBufferSize: maxBufferSize,
    62  		buffer:        make([]timestampedData, maxBufferSize),
    63  	}
    64  }
    65  
    66  func (a *MovingWindowAvgImpl) Record(val int64) {
    67  	a.Lock()
    68  	defer a.Unlock()
    69  
    70  	a.buffer[a.tailIdx] = timestampedData{timestamp: time.Now(), value: val}
    71  	a.tailIdx = (a.tailIdx + 1) % a.maxBufferSize
    72  
    73  	a.sum += val
    74  	a.count++
    75  
    76  	if a.tailIdx == a.headIdx {
    77  		// buffer full, expire oldest element
    78  		a.sum -= a.buffer[a.headIdx].value
    79  		a.count--
    80  		a.headIdx = (a.headIdx + 1) % a.maxBufferSize
    81  	}
    82  }
    83  
    84  func (a *MovingWindowAvgImpl) Average() float64 {
    85  	a.Lock()
    86  	defer a.Unlock()
    87  
    88  	a.expireOldValuesLocked()
    89  	if a.count == 0 {
    90  		return 0
    91  	}
    92  	return float64(a.sum) / float64(a.count)
    93  }
    94  
    95  func (a *MovingWindowAvgImpl) expireOldValuesLocked() {
    96  	for ; a.headIdx != a.tailIdx; a.headIdx = (a.headIdx + 1) % a.maxBufferSize {
    97  		if time.Since(a.buffer[a.headIdx].timestamp) < a.windowSize {
    98  			break
    99  		}
   100  		a.sum -= a.buffer[a.headIdx].value
   101  		a.count--
   102  	}
   103  }