139 lines
3.1 KiB
Markdown
139 lines
3.1 KiB
Markdown
# Backoff
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A simple backoff algorithm in Go (Golang)
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[](https://godoc.org/github.com/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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#### Credits
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Ported from some JavaScript written by [@tj](https://github.com/tj)
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#### MIT License
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Copyright © 2015 Jaime Pillora <dev@jpillora.com>
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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'Software'), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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