backoff

README

Backoff

A simple backoff algorithm in Go (Golang)

Install

$ go get -v github.com/jpillora/backoff

Usage

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). Used in conjunction with the time package.

---

Simple example

b := &backoff.Backoff{
	//These are the defaults
	Min:    100 * time.Millisecond,
	Max:    10 * time.Second,
	Factor: 2,
	Jitter: false,
}

fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())

fmt.Printf("Reset!\n")
b.Reset()

fmt.Printf("%s\n", b.Duration())

100ms
200ms
400ms
Reset!
100ms

---

Example using net package

b := &backoff.Backoff{
    Max:    5 * time.Minute,
}

for {
	conn, err := net.Dial("tcp", "example.com:5309")
	if err != nil {
		d := b.Duration()
		fmt.Printf("%s, reconnecting in %s", err, d)
		time.Sleep(d)
		continue
	}
	//connected
	b.Reset()
	conn.Write([]byte("hello world!"))
	// ... Read ... Write ... etc
	conn.Close()
	//disconnected
}

---

Example using Jitter

Enabling Jitter adds some randomization to the backoff durations. See Amazon's writeup of performance gains using jitter. Seeding is not necessary but doing so gives repeatable results.

import "math/rand"

b := &backoff.Backoff{
	Jitter: true,
}

rand.Seed(42)

fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())

fmt.Printf("Reset!\n")
b.Reset()

fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())
fmt.Printf("%s\n", b.Duration())

100ms
106.600049ms
281.228155ms
Reset!
100ms
104.381845ms
214.957989ms

Credits

Ported from some JavaScript written by @tj

MIT License

Copyright © 2015 Jaime Pillora <dev@jpillora.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Documentation

Index

• type Backoff
  • func (b *Backoff) Duration() time.Duration
  • func (b *Backoff) Reset()

Types

type Backoff

type Backoff struct {
	//Factor is the multiplying factor for each increment step
	Factor float64
	//Jitter eases contention by randomizing backoff steps
	Jitter bool
	//Min and Max are the minimum and maximum values of the counter
	Min, Max time.Duration
	// contains filtered or unexported fields
}

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(). Used in conjunction with the time package.

func (*Backoff) Duration

func (b *Backoff) Duration() time.Duration

Returns the current value of the counter and then multiplies it Factor

func (*Backoff) Reset

func (b *Backoff) Reset()

Resets the current value of the counter back to Min