retry

README

retry

A simple, stateless, functional mechanism to perform actions repetitively until successful.

Project Status

This project is currently in "pre-release". While the code is heavily tested, the API may change. Use a tagged version or vendor this dependency if you plan on using it.

That said, this code has been used in production without issue for years, and has been used by some relatively high-profile projects/codebases.

Examples

Basic

retry.Retry(func(attempt uint) error {
	return nil // Do something that may or may not cause an error
})

File Open

const logFilePath = "/var/log/myapp.log"

var logFile *os.File

err := retry.Retry(func(attempt uint) error {
	var err error

	logFile, err = os.Open(logFilePath)

	return err
})

if err != nil {
	log.Fatalf("Unable to open file %q with error %q", logFilePath, err)
}

logFile.Chdir() // Do something with the file

HTTP request with strategies and backoff

var response *http.Response

action := func(attempt uint) error {
	var err error

	response, err = http.Get("https://api.github.com/repos/Rican7/retry")

	if err == nil && response != nil && response.StatusCode > 200 {
		err = fmt.Errorf("failed to fetch (attempt #%d) with status code: %d", attempt, response.StatusCode)
	}

	return err
}

err := retry.Retry(
	action,
	strategy.Limit(5),
	strategy.Backoff(backoff.Fibonacci(10*time.Millisecond)),
)

if err != nil {
	log.Fatalf("Failed to fetch repository with error %q", err)
}

Retry with backoff jitter

action := func(attempt uint) error {
	return errors.New("something happened")
}

seed := time.Now().UnixNano()
random := rand.New(rand.NewSource(seed))

retry.Retry(
	action,
	strategy.Limit(5),
	strategy.BackoffWithJitter(
		backoff.BinaryExponential(10*time.Millisecond),
		jitter.Deviation(random, 0.5),
	),
)

Documentation

Overview

Package retry provides a simple, stateless, functional mechanism to perform actions repetitively until successful.

Copyright © 2016 Trevor N. Suarez (Rican7)

Example

package main

import (
	"github.com/Rican7/retry"
)

func main() {
	retry.Retry(func(attempt uint) error {
		return nil // Do something that may or may not cause an error
	})
}

Example (FileOpen)

package main

import (
	"log"
	"os"

	"github.com/Rican7/retry"
)

func main() {
	const logFilePath = "/var/log/myapp.log"

	var logFile *os.File

	err := retry.Retry(func(attempt uint) error {
		var err error

		logFile, err = os.Open(logFilePath)

		return err
	})

	if err != nil {
		log.Fatalf("Unable to open file %q with error %q", logFilePath, err)
	}

	logFile.Chdir() // Do something with the file
}

Example (HttpGetWithStrategies)

package main

import (
	"fmt"
	"log"
	"net/http"
	"time"

	"github.com/Rican7/retry"
	"github.com/Rican7/retry/backoff"
	"github.com/Rican7/retry/strategy"
)

func main() {
	var response *http.Response

	action := func(attempt uint) error {
		var err error

		response, err = http.Get("https://api.github.com/repos/Rican7/retry")

		if err == nil && response != nil && response.StatusCode > 200 {
			err = fmt.Errorf("failed to fetch (attempt #%d) with status code: %d", attempt, response.StatusCode)
		}

		return err
	}

	err := retry.Retry(
		action,
		strategy.Limit(5),
		strategy.Backoff(backoff.Fibonacci(10*time.Millisecond)),
	)

	if err != nil {
		log.Fatalf("Failed to fetch repository with error %q", err)
	}
}

Example (WithBackoffJitter)

package main

import (
	"errors"
	"fmt"
	"math/rand"
	"time"

	"github.com/Rican7/retry"
	"github.com/Rican7/retry/backoff"
	"github.com/Rican7/retry/jitter"
	"github.com/Rican7/retry/strategy"
)

func main() {
	action := func(attempt uint) error {
		fmt.Println("attempt", attempt)

		return errors.New("something happened")
	}

	seed := time.Now().UnixNano()
	random := rand.New(rand.NewSource(seed))

	retry.Retry(
		action,
		strategy.Limit(5),
		strategy.BackoffWithJitter(
			backoff.BinaryExponential(10*time.Millisecond),
			jitter.Deviation(random, 0.5),
		),
	)

}

Output:

attempt 1
attempt 2
attempt 3
attempt 4
attempt 5

Index

• func Retry(action Action, strategies ...strategy.Strategy) error
• type Action

Examples

• Package
• Package (FileOpen)
• Package (HttpGetWithStrategies)
• Package (WithBackoffJitter)

Functions

func Retry

func Retry(action Action, strategies ...strategy.Strategy) error

Retry takes an action and performs it, repetitively, until successful.

Optionally, strategies may be passed that assess whether or not an attempt should be made.

Types

type Action

type Action func(attempt uint) error

Action defines a callable function that package retry can handle.