1// Copyright 2012-present Oliver Eilhard. All rights reserved.
2// Use of this source code is governed by a MIT-license.
3// See http://olivere.mit-license.org/license.txt for details.
4
5// This file is based on code (c) 2014 Cenk Altı and governed by the MIT license.
6// See https://github.com/cenkalti/backoff for original source.
7
8package elastic
9
10import "time"
11
12// An Operation is executing by Retry() or RetryNotify().
13// The operation will be retried using a backoff policy if it returns an error.
14type Operation func() error
15
16// Notify is a notify-on-error function. It receives error returned
17// from an operation.
18//
19// Notice that if the backoff policy stated to stop retrying,
20// the notify function isn't called.
21type Notify func(error)
22
23// Retry the function f until it does not return error or BackOff stops.
24// f is guaranteed to be run at least once.
25// It is the caller's responsibility to reset b after Retry returns.
26//
27// Retry sleeps the goroutine for the duration returned by BackOff after a
28// failed operation returns.
29func Retry(o Operation, b Backoff) error { return RetryNotify(o, b, nil) }
30
31// RetryNotify calls notify function with the error and wait duration
32// for each failed attempt before sleep.
33func RetryNotify(operation Operation, b Backoff, notify Notify) error {
34	var err error
35	var wait time.Duration
36	var retry bool
37	var n int
38
39	for {
40		if err = operation(); err == nil {
41			return nil
42		}
43
44		n++
45		wait, retry = b.Next(n)
46		if !retry {
47			return err
48		}
49
50		if notify != nil {
51			notify(err)
52		}
53
54		time.Sleep(wait)
55	}
56}
57