goback

Documentation

Overview

Package goback implements a simple exponential backoff

An exponential backoff approach is typically used when treating with potentially faulty/slow systems. If a system fails quick retries may exacerbate the system specially when the system is dealing with several clients. In this case a backoff provides the faulty system enough room to recover.

Simple example:

 func main() {
	    b := &goback.SimpleBackoff(
		    Min:    100 * time.Millisecond,
		    Max:    60 * time.Second,
		    Factor: 2,
	    )
	    goback.Wait(b)           // sleeps 100ms
	    goback.Wait(b)           // sleeps 200ms
	    goback.Wait(b)           // sleeps 400ms
	    fmt.Println(b.NextRun()) // prints 800ms
	    b.Reset()                // resets the backoff
	    goback.Wait(b)           // sleeps 100ms
 }

Furter examples can be found in the examples folder in the repository.

Index

• Variables
• func After(b Backoff) <-chan error
• func GetNextDuration(min, max time.Duration, factor float64, attempts int) time.Duration
• func Wait(b Backoff) error
• type Backoff
• type JitterBackoff
  • func (b *JitterBackoff) NextAttempt() (time.Duration, error)
• type SimpleBackoff
  • func (b *SimpleBackoff) NextAttempt() (time.Duration, error)
  • func (b *SimpleBackoff) Reset()

Variables

var (
	// ErrMaxAttemptsExceeded indicates that the maximum retries has been
	// excedeed. Usually to consider a service unreachable/unavailable.
	ErrMaxAttemptsExceeded = errors.New("maximum of attempts exceeded")
)

Functions

func After

func After(b Backoff) <-chan error

After returns a channel that will be called after the time specified by the backoff strategy or will exit immediately with an error.

func GetNextDuration

func GetNextDuration(min, max time.Duration, factor float64, attempts int) time.Duration

GetNextDuration returns the duration for the strategies considering the minimum and maximum durations, the factor of increase and the number of attemtps tried.

func Wait

func Wait(b Backoff) error

Wait sleeps for the duration of the time specified by the backoff strategy.

Types

type Backoff

type Backoff interface {
	// NextAttempt returns the duration to wait for the next retry.
	NextAttempt() (time.Duration, error)
	// Reset clears the number of tries. Next call to NextAttempt will return
	// the minimum backoff time (if there is no error).
	Reset()
}

Backoff is the interface that any Backoff strategy needs to implement.

type JitterBackoff

type JitterBackoff SimpleBackoff

JitterBackoff provides an strategy similar to SimpleBackoff but lightly randomises the duration to minimise collisions between contending clients.

func (*JitterBackoff) NextAttempt

func (b *JitterBackoff) NextAttempt() (time.Duration, error)

NextAttempt returns the duration to wait for the next retry.

type SimpleBackoff

type SimpleBackoff struct {
	Attempts    int
	MaxAttempts int
	Factor      float64
	Min         time.Duration
	Max         time.Duration
}

SimpleBackoff provides a simple strategy to backoff.

func (*SimpleBackoff) NextAttempt

func (b *SimpleBackoff) NextAttempt() (time.Duration, error)

NextAttempt returns the duration to wait for the next retry.

func (*SimpleBackoff) Reset

func (b *SimpleBackoff) Reset()

Reset clears the number of tries. Next call to NextAttempt will return the minimum backoff time (if there is no error).