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