121 lines
2.8 KiB
Go
121 lines
2.8 KiB
Go
// Copyright 2018 Google LLC
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//
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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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// https://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 main
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import (
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"context"
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"math"
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"math/rand"
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"time"
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"github.com/google/alertmanager-irc-relay/logging"
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)
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type JitterFunc func(int) int
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type DelayerMaker interface {
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NewDelayer(float64, float64, time.Duration) Delayer
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}
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type Delayer interface {
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Delay()
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DelayContext(context.Context) bool
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}
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type Backoff struct {
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step float64
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maxBackoff float64
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resetDelta float64
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lastAttempt time.Time
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durationUnit time.Duration
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jitterer JitterFunc
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timeTeller TimeTeller
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}
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func jitterFunc(input int) int {
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if input == 0 {
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return 0
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}
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return rand.Intn(input)
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}
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type BackoffMaker struct{}
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func (bm *BackoffMaker) NewDelayer(maxBackoff float64, resetDelta float64, durationUnit time.Duration) Delayer {
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timeTeller := &RealTime{}
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return NewBackoffForTesting(
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maxBackoff, resetDelta, durationUnit, jitterFunc, timeTeller)
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}
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func NewBackoffForTesting(maxBackoff float64, resetDelta float64,
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durationUnit time.Duration, jitterer JitterFunc, timeTeller TimeTeller) *Backoff {
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return &Backoff{
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step: 0,
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maxBackoff: maxBackoff,
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resetDelta: resetDelta,
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lastAttempt: timeTeller.Now(),
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durationUnit: durationUnit,
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jitterer: jitterer,
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timeTeller: timeTeller,
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}
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}
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func (b *Backoff) maybeReset() {
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now := b.timeTeller.Now()
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lastAttemptDelta := float64(now.Sub(b.lastAttempt) / b.durationUnit)
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b.lastAttempt = now
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if lastAttemptDelta >= b.resetDelta {
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b.step = 0
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}
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}
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func (b *Backoff) GetDelay() time.Duration {
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b.maybeReset()
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var synchronizedDuration float64
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// Do not add any delay the first time.
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if b.step == 0 {
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synchronizedDuration = 0
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} else {
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synchronizedDuration = math.Pow(2, b.step)
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}
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if synchronizedDuration < b.maxBackoff {
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b.step++
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} else {
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synchronizedDuration = b.maxBackoff
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}
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duration := time.Duration(b.jitterer(int(synchronizedDuration)))
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return duration * b.durationUnit
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}
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func (b *Backoff) Delay() {
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b.DelayContext(context.Background())
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}
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func (b *Backoff) DelayContext(ctx context.Context) bool {
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delay := b.GetDelay()
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logging.Info("Backoff for %s starts", delay)
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select {
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case <-b.timeTeller.After(delay):
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logging.Info("Backoff for %s ends", delay)
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case <-ctx.Done():
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logging.Info("Backoff for %s canceled by context", delay)
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return false
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}
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return true
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}
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