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backoff.go
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backoff.go
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/*
Copyright 2018 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package backoff
import (
"time"
)
type backoffInfo struct {
duration time.Duration
backoffUntil time.Time
lastFailedExecution time.Time
}
// Backoff handles backing off executions.
type Backoff struct {
maxBackoffDuration time.Duration
initialBackoffDuration time.Duration
backoffResetTimeout time.Duration
backoffInfo map[string]backoffInfo
}
// NewBackoff creates an instance of Backoff.
func NewBackoff(initialBackoffDuration time.Duration, maxBackoffDuration time.Duration, backoffResetTimeout time.Duration) *Backoff {
return &Backoff{maxBackoffDuration, initialBackoffDuration, backoffResetTimeout, make(map[string]backoffInfo)}
}
// RemoveStaleBackoffData removes stale backoff data.
func (b *Backoff) RemoveStaleBackoffData(currentTime time.Time) {
for key, backoffInfo := range b.backoffInfo {
if backoffInfo.lastFailedExecution.Add(b.backoffResetTimeout).Before(currentTime) {
delete(b.backoffInfo, key)
}
}
}
// Backoff execution for the given key. Returns time till execution is backed off.
func (b *Backoff) Backoff(key string, currentTime time.Time) time.Time {
duration := b.initialBackoffDuration
if backoffInfo, found := b.backoffInfo[key]; found {
// Multiple concurrent scale-ups failing shouldn't cause backoff
// duration to increase, so we only increase it if we're not in
// backoff right now.
if backoffInfo.backoffUntil.Before(currentTime) {
duration = 2 * backoffInfo.duration
if duration > b.maxBackoffDuration {
duration = b.maxBackoffDuration
}
}
}
backoffUntil := currentTime.Add(duration)
b.backoffInfo[key] = backoffInfo{
duration: duration,
backoffUntil: backoffUntil,
lastFailedExecution: currentTime,
}
return backoffUntil
}
// RemoveBackoff removes backoff data for the given key.
func (b *Backoff) RemoveBackoff(key string) {
delete(b.backoffInfo, key)
}
// IsBackedOff returns true if execution is backed off for the given key.
func (b *Backoff) IsBackedOff(key string, currentTime time.Time) bool {
backoffInfo, found := b.backoffInfo[key]
return found && backoffInfo.backoffUntil.After(currentTime)
}