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120 lines
2.3 KiB
Markdown
120 lines
2.3 KiB
Markdown
# Backoff
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A simple exponential backoff counter in Go (Golang)
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[](https://godoc.org/github.com/jpillora/backoff) [](https://circleci.com/gh/jpillora/backoff)
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### Install
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```
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$ go get -v github.com/jpillora/backoff
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```
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### Usage
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Backoff is a `time.Duration` counter. It starts at `Min`. After every call to `Duration()` it is multiplied by `Factor`. It is capped at `Max`. It returns to `Min` on every call to `Reset()`. `Jitter` adds randomness ([see below](#example-using-jitter)). Used in conjunction with the `time` package.
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---
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#### Simple example
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``` go
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b := &backoff.Backoff{
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//These are the defaults
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Min: 100 * time.Millisecond,
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Max: 10 * time.Second,
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Factor: 2,
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Jitter: false,
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}
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fmt.Printf("%s\n", b.Duration())
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fmt.Printf("%s\n", b.Duration())
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fmt.Printf("%s\n", b.Duration())
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fmt.Printf("Reset!\n")
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b.Reset()
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fmt.Printf("%s\n", b.Duration())
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```
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```
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100ms
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200ms
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400ms
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Reset!
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100ms
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```
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---
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#### Example using `net` package
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``` go
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b := &backoff.Backoff{
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Max: 5 * time.Minute,
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}
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for {
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conn, err := net.Dial("tcp", "example.com:5309")
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if err != nil {
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d := b.Duration()
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fmt.Printf("%s, reconnecting in %s", err, d)
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time.Sleep(d)
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continue
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}
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//connected
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b.Reset()
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conn.Write([]byte("hello world!"))
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// ... Read ... Write ... etc
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conn.Close()
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//disconnected
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}
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```
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---
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#### Example using `Jitter`
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Enabling `Jitter` adds some randomization to the backoff durations. [See Amazon's writeup of performance gains using jitter](http://www.awsarchitectureblog.com/2015/03/backoff.html). Seeding is not necessary but doing so gives repeatable results.
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```go
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import "math/rand"
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b := &backoff.Backoff{
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Jitter: true,
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}
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rand.Seed(42)
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fmt.Printf("%s\n", b.Duration())
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fmt.Printf("%s\n", b.Duration())
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fmt.Printf("%s\n", b.Duration())
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fmt.Printf("Reset!\n")
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b.Reset()
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fmt.Printf("%s\n", b.Duration())
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fmt.Printf("%s\n", b.Duration())
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fmt.Printf("%s\n", b.Duration())
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```
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```
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100ms
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106.600049ms
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281.228155ms
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Reset!
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100ms
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104.381845ms
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214.957989ms
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```
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#### Documentation
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https://godoc.org/github.com/jpillora/backoff
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#### Credits
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Forked from [some JavaScript](https://github.com/segmentio/backo) written by [@tj](https://github.com/tj)
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