retry

README

retry

An exponentially backing off retry package for Go.

go get github.com/coder/retry@latest

retry promotes control flow using for/goto instead of callbacks.

Examples

Wait for connectivity to google.com, checking at most once every second:

func pingGoogle(ctx context.Context) error {
	var err error

	r := retry.New(time.Second, time.Second*10);

	// Jitter is useful when the majority of clients to a service use
	// the same backoff policy.
	//
	// It is provided as a standard deviation.
	r.Jitter = 0.1

  retry:
	_, err = http.Get("https://google.com")
	if err != nil {
		if r.Wait(ctx) {
			goto retry
		}
		return err
	}

	return nil
}

Wait for connectivity to google.com, checking at most 10 times:

func pingGoogle(ctx context.Context) error {
	var err error
	
	for r := retry.New(time.Second, time.Second*10); n := 0; r.Wait(ctx) && n < 10; n++ {
		_, err = http.Get("https://google.com")
		if err != nil {
			continue
		}
		break
	}
	return err
}

Documentation

Overview

Package retry runs a fallible block of code until it succeeds.

Index

• type Retrier
  • func New(floor, ceil time.Duration) *Retrier
  • func (r *Retrier) Reset()
  • func (r *Retrier) Wait(ctx context.Context) bool

Types

type Retrier

type Retrier struct {
	// Delay is the current delay between attempts.
	Delay time.Duration

	// Floor and Ceil are the minimum and maximum delays.
	Floor, Ceil time.Duration

	// Rate is the rate at which the delay grows.
	// E.g. 2 means the delay doubles each time.
	Rate float64

	// Jitter determines the level of indeterminism in the delay.
	//
	// It is the standard deviation of the normal distribution of a random variable
	// multiplied by the delay. E.g. 0.1 means the delay is normally distributed
	// with a standard deviation of 10% of the delay. Floor and Ceil are still
	// respected, making outlandish values impossible.
	//
	// Jitter can help avoid thundering herds.
	Jitter float64
}

Retrier implements an exponentially backing off retry instance. Use New instead of creating this object directly.

func New

func New(floor, ceil time.Duration) *Retrier

New creates a retrier that exponentially backs off from floor to ceil pauses.

func (*Retrier) Reset

func (r *Retrier) Reset()

Reset resets the retrier to its initial state.

func (*Retrier) Wait

func (r *Retrier) Wait(ctx context.Context) bool

Wait returns after min(Delay*Growth, Ceil) or ctx is cancelled. The first call to Wait will return immediately.