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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

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:

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 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:

const pRetry = require('p-retry');

const run = async emoji => {
	// …
};

(async () => {
	// Without arguments
	await pRetry(run, {retries: 5});

	// With arguments
	await pRetry(() => run('🦄'), {retries: 5});
})();

p-timeout - Timeout a promise after a specified amount of time
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