repeater

README

Repeater

Repeater calls a function until it returns no error, up to some number of iterations and delays defined by strategy. It terminates immediately on err from the provided (optional) list of critical errors.

Install and update

go get -u github.com/go-pkgz/repeater

How to use

New Repeater created by New(strtg strategy.Interface) or shortcut for defaults - NewDefault(repeats int, delay time.Duration) *Repeater.

To activate invoke Do method. Do repeats func until no error returned. Predefined (optional) errors terminates the loop immediately.

func (r Repeater) Do(ctx context.Context, fun func() error, errors ...error) (err error)

Repeating strategy

User can provide his own strategy implementing the interface:

type Interface interface {
	Start(ctx context.Context) chan struct{}
}

Returned channels used as "ticks," i.e., for each repeat or initial operation one read from this channel needed. Closing this channel indicates "done with retries." It is pretty much the same idea as time.Timer or time.Tick implements. Note - the first (technically not-repeated-yet) call won't happen until something sent to the channel. For this reason, the typical strategy sends the first "tick" before the first wait/sleep.

Three most common strategies provided by package and ready to use:

1. Fixed delay, up to max number of attempts - NewFixedDelay(repeats int, delay time.Duration). It is the default strategy used by repeater.NewDefault constructor
2. BackOff with jitter provides exponential backoff. It starts from 100ms interval and goes in steps with last * math.Pow(factor, attempt). Optional jitter randomizes intervals a little bit. The strategy created by NewBackoff(repeats int, factor float64, jitter bool). Factor = 1 effectively makes this strategy fixed with 100ms delay.
3. Once strategy does not do any repeats and mainly used for tests/mocks - NewOnce()

Documentation

Overview

Package repeater call fun till it returns no error, up to repeat some number of iterations and delays defined by strategy. Repeats number and delays defined by strategy.Interface. Terminates immediately on err from provided, optional list of critical errors

Index

• type Repeater
  • func New(strtg strategy.Interface) *Repeater
  • func NewDefault(repeats int, delay time.Duration) *Repeater
  • func (r Repeater) Do(ctx context.Context, fun func() error, errors ...error) (err error)

Types

type Repeater

type Repeater struct {
	strategy.Interface
}

Repeater is the main object, should be made by New or NewDefault, embeds strategy

func New

func New(strtg strategy.Interface) *Repeater

New repeater with a given strategy. If strategy=nil initializes with FixedDelay 5sec, 10 times.

func NewDefault

func NewDefault(repeats int, delay time.Duration) *Repeater

NewDefault makes repeater with FixedDelay strategy

func (Repeater) Do

func (r Repeater) Do(ctx context.Context, fun func() error, errors ...error) (err error)

Do repeats fun till no error. Predefined (optional) errors terminate immediately