async-retry

What is async-retry?

The async-retry npm package is designed to handle the execution of asynchronous operations that may fail by retrying them a specified number of times with customizable options. It is useful for dealing with operations like network requests or any other tasks that might intermittently fail due to temporary issues.

What are async-retry's main functionalities?

Basic retry functionality

This feature allows you to automatically retry an asynchronous operation if it fails. The code sample shows how to use async-retry to fetch data from an API with up to 5 retries.

const retry = require('async-retry');

async function fetchData() {
  return retry(async bail => {
    // if anything throws, we retry
    const result = await fetch('https://api.example.com/data');
    if (result.status >= 400) {
      throw new Error('Request failed');
    }
    return result.json();
  }, {
    retries: 5
  });
}

Custom retry strategies

This feature allows you to define a custom retry strategy, including the number of retries, the factor by which the timeout increases, and the minimum and maximum timeout values. The code sample demonstrates setting these options for a more sophisticated retry strategy.

const retry = require('async-retry');

async function fetchDataWithCustomStrategy() {
  return retry(async bail => {
    // if anything throws, we retry
    const result = await fetch('https://api.example.com/data');
    if (result.status >= 400) {
      throw new Error('Request failed');
    }
    return result.json();
  }, {
    retries: 5,
    factor: 2,
    minTimeout: 1000,
    maxTimeout: 5000,
    randomize: true
  });
}

Bailing out of retries

This feature allows you to bail out of the retry loop early under certain conditions. The code sample shows how to stop retrying if a 404 status is encountered or after a certain number of attempts.

const retry = require('async-retry');

async function fetchDataWithBail() {
  return retry(async (bail, attempt) => {
    try {
      const result = await fetch('https://api.example.com/data');
      if (result.status === 404) {
        // Don't retry upon 404
        bail(new Error('Not found'));
        return;
      }
      return result.json();
    } catch (error) {
      if (attempt >= 3) {
        // Bail on the third attempt
        bail(error);
        return;
      }
      throw error;
    }
  }, {
    retries: 5
  });
}

Other packages similar to async-retry

retry

The 'retry' package provides similar functionality for retrying operations, with a focus on both synchronous and asynchronous control flow. It offers a more extensive set of options for customizing retry behavior but does not provide an async/await interface out of the box.

p-retry

The 'p-retry' package is another alternative that supports retrying asynchronous operations using Promises. It has a similar API to async-retry but is built specifically for use with Promises and provides slightly different options for customizing the retry behavior.

retry-axios

The 'retry-axios' package is designed to work as an interceptor for axios, a popular HTTP client. It allows you to automatically retry failed HTTP requests, and it is specifically tailored for axios users, unlike async-retry which is more generic and can be used with any asynchronous operation.

README

async-retry

Retrying made simple, easy, and async.

Usage

// Packages
const retry = require('async-retry')
const fetch = require('node-fetch')

await retry(async bail => {
  // if anything throws, we retry
  const res = await fetch('https://google.com')

  if (403 === res.status) {
    // don't retry upon 403
    bail(new Error('Unauthorized'))
    return
  }

  const data = await res.text()
  return data.substr(0, 500)
}, {
  retries: 5
})

API

retry(retrier : Function, opts : Object) => Promise

• The supplied function can be async or not. In other words, it can be a function that returns a Promise or a value.
• The supplied function receives two parameters
  1. A Function you can invoke to abort the retrying (bail)
  2. A Number identifying the attempt. The absolute first attempt (before any retries) is 1.
• The opts are passed to node-retry. Read its docs
  • retries: The maximum amount of times to retry the operation. Default is 10.
  • factor: The exponential factor to use. Default is 2.
  • minTimeout: The number of milliseconds before starting the first retry. Default is 1000.
  • maxTimeout: The maximum number of milliseconds between two retries. Default is Infinity.
  • randomize: Randomizes the timeouts by multiplying with a factor between 1 to 2. Default is true.
  • onRetry: an optional Function that is invoked after a new retry is performed. It's passed the Error that triggered it as a parameter.

Authors

• Guillermo Rauch (@rauchg) - ZEIT
• Leo Lamprecht (@notquiteleo) - ZEIT