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// Copyright 2016 Google Inc. All Rights Reserved.
// 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package internal
import (
gax ""
// Retry calls the supplied function f repeatedly according to the provided
// backoff parameters. It returns when one of the following occurs:
// When f's first return value is true, Retry immediately returns with f's second
// return value.
// When the provided context is done, Retry returns with an error that
// includes both ctx.Error() and the last error returned by f.
func Retry(ctx context.Context, bo gax.Backoff, f func() (stop bool, err error)) error {
return retry(ctx, bo, f, gax.Sleep)
func retry(ctx context.Context, bo gax.Backoff, f func() (stop bool, err error),
sleep func(context.Context, time.Duration) error) error {
var lastErr error
for {
stop, err := f()
if stop {
return err
// Remember the last "real" error from f.
if err != nil && err != context.Canceled && err != context.DeadlineExceeded {
lastErr = err
p := bo.Pause()
if cerr := sleep(ctx, p); cerr != nil {
if lastErr != nil {
return fmt.Errorf("%v; last function err: %v", cerr, lastErr)
return cerr