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# backoff
## Go implementation of "Exponential Backoff And Jitter"
This package implements the backoff strategy described in the AWS
Architecture Blog article
["Exponential Backoff And Jitter"](http://www.awsarchitectureblog.com/2015/03/backoff.html). Essentially,
the backoff has an interval `time.Duration`; the *n<sup>th</sup>* call
to backoff will return an a `time.Duration` that is *2 <sup>n</sup> *
interval*. If jitter is enabled (which is the default behaviour), the
duration is a random value between 0 and *2 <sup>n</sup> * interval*.
The backoff is configured with a maximum duration that will not be
exceeded; e.g., by default, the longest duration returned is
`backoff.DefaultMaxDuration`.
## Usage
A `Backoff` is initialised with a call to `New`. Using zero values
causes it to use `DefaultMaxDuration` and `DefaultInterval` as the
maximum duration and interval.
```
package something
import "github.com/cloudflare/backoff"
func retryable() {
b := backoff.New(0, 0)
for {
err := someOperation()
if err == nil {
break
}
log.Printf("error in someOperation: %v", err)
<-time.After(b.Duration())
}
log.Printf("succeeded after %d tries", b.Tries()+1)
b.Reset()
}
```
It can also be used to rate limit code that should retry infinitely, but which does not
use `Backoff` itself.
```
package something
import (
"time"
"github.com/cloudflare/backoff"
)
func retryable() {
b := backoff.New(0, 0)
b.SetDecay(30 * time.Second)
for {
// b will reset if someOperation returns later than
// the last call to b.Duration() + 30s.
err := someOperation()
if err == nil {
break
}
log.Printf("error in someOperation: %v", err)
<-time.After(b.Duration())
}
}
```
## Tunables
* `NewWithoutJitter` creates a Backoff that doesn't use jitter.
The default behaviour is controlled by two variables:
* `DefaultInterval` sets the base interval for backoffs created with
the zero `time.Duration` value in the `Interval` field.
* `DefaultMaxDuration` sets the maximum duration for backoffs created
with the zero `time.Duration` value in the `MaxDuration` field.
|
