cfssl/vendor/github.com/cloudflare/backoff

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". Essentially, the backoff has an interval time.Duration; the n^th call to backoff will return an a time.Duration that is *2 ⁿ * interval*. If jitter is enabled (which is the default behaviour), the duration is a random value between 0 and *2 ⁿ * 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.