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93 lines
2.9 KiB
Go
93 lines
2.9 KiB
Go
// Copyright (c) 2015-2021 MinIO, Inc.
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//
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// This file is part of MinIO Object Storage stack
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package bandwidth
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import (
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"sync"
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"sync/atomic"
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"time"
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)
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const (
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// betaBucket is the weight used to calculate exponential moving average
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betaBucket = 0.1 // Number of averages considered = 1/(1-betaObject)
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)
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// bucketMeasurement captures the bandwidth details for one bucket
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type bucketMeasurement struct {
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lock sync.Mutex
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bytesSinceLastWindow uint64 // Total bytes since last window was processed
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startTime time.Time // Start time for window
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expMovingAvg float64 // Previously calculate sliding window
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}
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// newBucketMeasurement creates a new instance of the measurement with the initial start time.
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func newBucketMeasurement(initTime time.Time) *bucketMeasurement {
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return &bucketMeasurement{
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startTime: initTime,
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}
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}
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// incrementBytes add bytes reported for a bucket.
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func (m *bucketMeasurement) incrementBytes(bytes uint64) {
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atomic.AddUint64(&m.bytesSinceLastWindow, bytes)
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}
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// updateExponentialMovingAverage processes the measurements captured so far.
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func (m *bucketMeasurement) updateExponentialMovingAverage(endTime time.Time) {
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// Calculate aggregate avg bandwidth and exp window avg
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m.lock.Lock()
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defer func() {
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m.startTime = endTime
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m.lock.Unlock()
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}()
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if m.startTime.IsZero() {
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return
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}
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if endTime.Before(m.startTime) {
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return
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}
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duration := endTime.Sub(m.startTime)
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bytesSinceLastWindow := atomic.SwapUint64(&m.bytesSinceLastWindow, 0)
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if m.expMovingAvg == 0 {
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// Should address initial calculation and should be fine for resuming from 0
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m.expMovingAvg = float64(bytesSinceLastWindow) / duration.Seconds()
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return
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}
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increment := float64(bytesSinceLastWindow) / duration.Seconds()
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m.expMovingAvg = exponentialMovingAverage(betaBucket, m.expMovingAvg, increment)
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}
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// exponentialMovingAverage calculates the exponential moving average
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func exponentialMovingAverage(beta, previousAvg, incrementAvg float64) float64 {
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return (1-beta)*incrementAvg + beta*previousAvg
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}
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// getExpMovingAvgBytesPerSecond returns the exponential moving average for the bucket in bytes
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func (m *bucketMeasurement) getExpMovingAvgBytesPerSecond() float64 {
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m.lock.Lock()
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defer m.lock.Unlock()
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return m.expMovingAvg
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}
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