71 lines
1.9 KiB
Go
71 lines
1.9 KiB
Go
// Copyright 2013 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package remote
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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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// ewmaRate tracks an exponentially weighted moving average of a per-second rate.
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type ewmaRate struct {
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// Keep all 64bit atomically accessed variables at the top of this struct.
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// See https://golang.org/pkg/sync/atomic/#pkg-note-BUG for more info.
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newEvents int64
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alpha float64
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interval time.Duration
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lastRate float64
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init bool
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mutex sync.Mutex
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}
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// newEWMARate always allocates a new ewmaRate, as this guarantees the atomically
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// accessed int64 will be aligned on ARM. See prometheus#2666.
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func newEWMARate(alpha float64, interval time.Duration) *ewmaRate {
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return &ewmaRate{
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alpha: alpha,
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interval: interval,
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}
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}
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// rate returns the per-second rate.
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func (r *ewmaRate) rate() float64 {
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r.mutex.Lock()
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defer r.mutex.Unlock()
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return r.lastRate
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}
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// tick assumes to be called every r.interval.
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func (r *ewmaRate) tick() {
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newEvents := atomic.SwapInt64(&r.newEvents, 0)
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instantRate := float64(newEvents) / r.interval.Seconds()
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r.mutex.Lock()
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defer r.mutex.Unlock()
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if r.init {
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r.lastRate += r.alpha * (instantRate - r.lastRate)
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} else if newEvents > 0 {
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r.init = true
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r.lastRate = instantRate
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}
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}
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// inc counts one event.
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func (r *ewmaRate) incr(incr int64) {
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atomic.AddInt64(&r.newEvents, incr)
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}
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