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    p-retry
    TypeScript icon, indicating that this package has built-in type declarations

    4.5.0 • Public • Published

    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}));
    })();

    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 maximum number of retries is reached. It then rejects with the last rejection reason.

    Does not retry on most TypeErrors, with the exception of network errors. This is done on a best case basis as different browsers have different messages to indicate this. See whatwg/fetch#526 (comment)

    input

    Type: Function

    Receives the current attempt number 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.

    const run = async () => {
    	const response = await fetch('https://sindresorhus.com/unicorn');
    
    	if (!response.ok) {
    		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);
    })();

    The onFailedAttempt function can return a promise. For example, you can do some async logging:

    const pRetry = require('p-retry');
    const logger = require('./some-logger);
    
    const run = async () => { … };
    
    (async () => {
    	const result = await pRetry(run, {
    		onFailedAttempt: async error => {
    			await logger.log(error);
    		}
    	});
    })();

    If the onFailedAttempt function throws, all retries will be aborted and the original promise will reject with the thrown error.

    pRetry.AbortError(message)

    pRetry.AbortError(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});
    })();

    Related

    Install

    npm i p-retry

    DownloadsWeekly Downloads

    7,207,850

    Version

    4.5.0

    License

    MIT

    Unpacked Size

    11 kB

    Total Files

    5

    Last publish

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