mirror of
https://github.com/prometheus/alertmanager
synced 2024-12-11 08:55:56 +00:00
117 lines
3.1 KiB
Markdown
117 lines
3.1 KiB
Markdown
# Exponential Backoff [![GoDoc][godoc image]][godoc] [![Build Status][travis image]][travis]
|
|
|
|
This is a Go port of the exponential backoff algorithm from [Google's HTTP Client Library for Java][google-http-java-client].
|
|
|
|
[Exponential backoff][exponential backoff wiki]
|
|
is an algorithm that uses feedback to multiplicatively decrease the rate of some process,
|
|
in order to gradually find an acceptable rate.
|
|
The retries exponentially increase and stop increasing when a certain threshold is met.
|
|
|
|
## How To
|
|
|
|
We define two functions, `Retry()` and `RetryNotify()`.
|
|
They receive an `Operation` to execute, a `BackOff` algorithm,
|
|
and an optional `Notify` error handler.
|
|
|
|
The operation will be executed, and will be retried on failure with delay
|
|
as given by the backoff algorithm. The backoff algorithm can also decide when to stop
|
|
retrying.
|
|
In addition, the notify error handler will be called after each failed attempt,
|
|
except for the last time, whose error should be handled by the caller.
|
|
|
|
```go
|
|
// An Operation is executing by Retry() or RetryNotify().
|
|
// The operation will be retried using a backoff policy if it returns an error.
|
|
type Operation func() error
|
|
|
|
// Notify is a notify-on-error function. It receives an operation error and
|
|
// backoff delay if the operation failed (with an error).
|
|
//
|
|
// NOTE that if the backoff policy stated to stop retrying,
|
|
// the notify function isn't called.
|
|
type Notify func(error, time.Duration)
|
|
|
|
func Retry(Operation, BackOff) error
|
|
func RetryNotify(Operation, BackOff, Notify)
|
|
```
|
|
|
|
## Examples
|
|
|
|
See more advanced examples in the [godoc][advanced example].
|
|
|
|
### Retry
|
|
|
|
Simple retry helper that uses the default exponential backoff algorithm:
|
|
|
|
```go
|
|
operation := func() error {
|
|
// An operation that might fail.
|
|
return nil // or return errors.New("some error")
|
|
}
|
|
|
|
err := Retry(operation, NewExponentialBackOff())
|
|
if err != nil {
|
|
// Handle error.
|
|
return err
|
|
}
|
|
|
|
// Operation is successful.
|
|
return nil
|
|
```
|
|
|
|
### Ticker
|
|
|
|
```go
|
|
operation := func() error {
|
|
// An operation that might fail
|
|
return nil // or return errors.New("some error")
|
|
}
|
|
|
|
b := NewExponentialBackOff()
|
|
ticker := NewTicker(b)
|
|
|
|
var err error
|
|
|
|
// Ticks will continue to arrive when the previous operation is still running,
|
|
// so operations that take a while to fail could run in quick succession.
|
|
for range ticker.C {
|
|
if err = operation(); err != nil {
|
|
log.Println(err, "will retry...")
|
|
continue
|
|
}
|
|
|
|
ticker.Stop()
|
|
break
|
|
}
|
|
|
|
if err != nil {
|
|
// Operation has failed.
|
|
return err
|
|
}
|
|
|
|
// Operation is successful.
|
|
return nil
|
|
```
|
|
|
|
## Getting Started
|
|
|
|
```bash
|
|
# install
|
|
$ go get github.com/cenkalti/backoff
|
|
|
|
# test
|
|
$ cd $GOPATH/src/github.com/cenkalti/backoff
|
|
$ go get -t ./...
|
|
$ go test -v -cover
|
|
```
|
|
|
|
[godoc]: https://godoc.org/github.com/cenkalti/backoff
|
|
[godoc image]: https://godoc.org/github.com/cenkalti/backoff?status.png
|
|
[travis]: https://travis-ci.org/cenkalti/backoff
|
|
[travis image]: https://travis-ci.org/cenkalti/backoff.png
|
|
|
|
[google-http-java-client]: https://github.com/google/google-http-java-client
|
|
[exponential backoff wiki]: http://en.wikipedia.org/wiki/Exponential_backoff
|
|
|
|
[advanced example]: https://godoc.org/github.com/cenkalti/backoff#example_
|