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exponential.go
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exponential.go
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// Copyright Istio 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 is a wrapper of `github.com/cenkalti/backoff/v4`.
// It is to prevent misuse of `github.com/cenkalti/backoff/v4`,
// thus application could fall into dead loop.
package backoff
import (
"context"
"fmt"
"time"
"github.com/cenkalti/backoff/v4"
)
// BackOff is a backoff policy for retrying an operation.
type BackOff interface {
// NextBackOff returns the duration to wait before retrying the next operation.
NextBackOff() time.Duration
// Reset to initial state.
Reset()
// RetryWithContext tries the operation until it does not return error,
// or when the context expires, whichever happens first.
RetryWithContext(ctx context.Context, operation func() error) error
}
type Option struct {
InitialInterval time.Duration
MaxInterval time.Duration
}
// ExponentialBackOff is a wrapper of backoff.ExponentialBackOff to override its NextBackOff().
type ExponentialBackOff struct {
exponentialBackOff *backoff.ExponentialBackOff
}
// Default values for ExponentialBackOff.
const (
defaultInitialInterval = 500 * time.Millisecond
defaultMaxInterval = 60 * time.Second
)
func DefaultOption() Option {
return Option{
InitialInterval: defaultInitialInterval,
MaxInterval: defaultMaxInterval,
}
}
// NewExponentialBackOff creates an istio wrapped ExponentialBackOff.
// By default, it never stops.
func NewExponentialBackOff(o Option) BackOff {
b := ExponentialBackOff{}
b.exponentialBackOff = backoff.NewExponentialBackOff()
b.exponentialBackOff.InitialInterval = o.InitialInterval
b.exponentialBackOff.MaxInterval = o.MaxInterval
b.Reset()
return b
}
func (b ExponentialBackOff) NextBackOff() time.Duration {
duration := b.exponentialBackOff.NextBackOff()
// always return maxInterval after it reaches MaxElapsedTime
if duration == b.exponentialBackOff.Stop {
return b.exponentialBackOff.MaxInterval
}
return duration
}
func (b ExponentialBackOff) Reset() {
b.exponentialBackOff.Reset()
}
// RetryWithContext tries the operation until it does not return error,
// or when the context expires, whichever happens first.
// o is guaranteed to be run at least once.
// RetryWithContext sleeps the goroutine for the duration returned by BackOff after a
// failed operation returns.
func (b ExponentialBackOff) RetryWithContext(ctx context.Context, operation func() error) error {
b.Reset()
for {
err := operation()
if err == nil {
return nil
}
next := b.NextBackOff()
select {
case <-ctx.Done():
return fmt.Errorf("%v with last error: %v", context.DeadlineExceeded, err)
case <-time.After(next):
}
}
}