# p-retry [![Build Status](https://travis-ci.org/sindresorhus/p-retry.svg?branch=master)](https://travis-ci.org/sindresorhus/p-retry) > Retry a promise-returning or async function It does exponential backoff and supports custom retry strategies for failed operations. ## Install ``` $ npm install p-retry ``` ## Usage ```js const pRetry = require('p-retry'); const fetch = require('node-fetch'); const run = async () => { const response = await fetch('https://sindresorhus.com/unicorn'); // Abort retrying if the resource doesn't exist if (response.status === 404) { throw new pRetry.AbortError(response.statusText); } return response.blob(); }; (async () => { console.log(await pRetry(run, {retries: 5})); })(); ``` With the `onFailedAttempt` option: ```js const run = async () => { const response = await fetch('https://sindresorhus.com/unicorn'); if (response.status !== 200) { throw new Error(response.statusText); } return response.json(); }; (async () => { const result = await pRetry(run, { onFailedAttempt: error => { console.log(`Attempt ${error.attemptNumber} failed. There are ${error.retriesLeft} retries left.`); // 1st request => Attempt 1 failed. There are 4 retries left. // 2nd request => Attempt 2 failed. There are 3 retries left. // … }, retries: 5 }); console.log(result); })(); ``` ## API ### pRetry(input, [options]) Returns a `Promise` that is fulfilled when calling `input` returns a fulfilled promise. If calling `input` returns a rejected promise, `input` is called again until the max retries are reached, it then rejects with the last rejection reason. It doesn't retry on `TypeError` as that's a user error. #### input Type: `Function` Receives the number of attempts as the first argument and is expected to return a `Promise` or any value. #### options Type: `Object` Options are passed to the [`retry`](https://github.com/tim-kos/node-retry#retryoperationoptions) module. ##### onFailedAttempt(error) Type: `Function` Callback invoked on each retry. Receives the error thrown by `input` as the first argument with properties `attemptNumber` and `retriesLeft` which indicate the current attempt number and the number of attempts left, respectively. ### pRetry.AbortError(message|error) Abort retrying and reject the promise. ### message Type: `string` Error message. ### error Type: `Error` Custom error. ## Tip You can pass arguments to the function being retried by wrapping it in an inline arrow function: ```js const pRetry = require('p-retry'); const run = async emoji => { // … }; (async () => { // Without arguments await pRetry(run, {retries: 5}); // With arguments await pRetry(() => run('🦄'), {retries: 5}); })(); ``` ## Related - [p-timeout](https://github.com/sindresorhus/p-timeout) - Timeout a promise after a specified amount of time - [More…](https://github.com/sindresorhus/promise-fun) ## License MIT © [Sindre Sorhus](https://sindresorhus.com)