agola/internal/util/backoff.go

113 lines
3.5 KiB
Go

// Copyright 2019 Sorint.lab
//
// 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 util
import (
"context"
"errors"
"math/rand"
"time"
)
// DefaultRetry is the recommended retry for a conflict where multiple clients
// are making changes to the same resource.
var DefaultRetry = Backoff{
Steps: 5,
Duration: 10 * time.Millisecond,
Factor: 1.0,
Jitter: 0.1,
}
// DefaultBackoff is the recommended backoff for a conflict where a client
// may be attempting to make an unrelated modification to a resource under
// active management by one or more controllers.
var DefaultBackoff = Backoff{
Steps: 4,
Duration: 10 * time.Millisecond,
Factor: 5.0,
Jitter: 0.1,
}
// DefaultBackoff is the recommended backoff for a conflict where a client
// may be attempting to make an unrelated modification to a resource under
// active management by one or more controllers.
var FetchFileBackoff = Backoff{
Steps: 4,
Duration: 500 * time.Millisecond,
Factor: 2.0,
Jitter: 0.1,
}
// Jitter returns a time.Duration between duration and duration + maxFactor *
// duration.
//
// This allows clients to avoid converging on periodic behavior. If maxFactor
// is 0.0, a suggested default value will be chosen.
func Jitter(duration time.Duration, maxFactor float64) time.Duration {
if maxFactor <= 0.0 {
maxFactor = 1.0
}
wait := duration + time.Duration(rand.Float64()*maxFactor*float64(duration))
return wait
}
// ErrWaitTimeout is returned when the condition exited without success.
var ErrWaitTimeout = errors.New("timed out waiting for the condition")
// ConditionFunc returns true if the condition is satisfied, or an error
// if the loop should be aborted.
type ConditionFunc func() (done bool, err error)
// Backoff holds parameters applied to a Backoff function.
type Backoff struct {
Duration time.Duration // the base duration
Factor float64 // Duration is multiplied by factor each iteration
Jitter float64 // The amount of jitter applied each iteration
Steps int // Exit with error after this many steps
}
// ExponentialBackoff repeats a condition check with exponential backoff.
//
// It checks the condition up to Steps times, increasing the wait by multiplying
// the previous duration by Factor.
//
// If Jitter is greater than zero, a random amount of each duration is added
// (between duration and duration*(1+jitter)).
//
// If the condition never returns true, ErrWaitTimeout is returned. All other
// errors terminate immediately.
func ExponentialBackoff(ctx context.Context,backoff Backoff, condition ConditionFunc) error {
duration := backoff.Duration
for i := 0; i < backoff.Steps; i++ {
if i != 0 {
adjusted := duration
if backoff.Jitter > 0.0 {
adjusted = Jitter(duration, backoff.Jitter)
}
sleepCh := time.NewTimer(adjusted).C
select {
case <-ctx.Done():
return nil
case <-sleepCh:
}
duration = time.Duration(float64(duration) * backoff.Factor)
}
if ok, err := condition(); err != nil || ok {
return err
}
}
return ErrWaitTimeout
}