Retry a promise-returning or async function
It does exponential backoff and supports custom retry strategies for failed operations.
npm install p-retryimport pRetry, {AbortError} from 'p-retry';
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 AbortError(response.statusText);
}
return response.blob();
};
console.log(await pRetry(run, {retries: 5}));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.
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)
Type: Function
Receives the number of attempts as the first argument and is expected to return a Promise or any value.
Type: object
Type: Function
Callback invoked on each retry. Receives a context object containing the error and retry state information.
import pRetry from 'p-retry';
const run = async () => {
const response = await fetch('https://sindresorhus.com/unicorn');
if (!response.ok) {
throw new Error(response.statusText);
}
return response.json();
};
const result = await pRetry(run, {
onFailedAttempt: ({error, attemptNumber, retriesLeft}) => {
console.log(`Attempt ${attemptNumber} failed. There are ${retriesLeft} retries left.`);
// 1st request => Attempt 1 failed. There are 5 retries left.
// 2nd request => Attempt 2 failed. There are 4 retries left.
// …
},
retries: 5
});
console.log(result);The onFailedAttempt function can return a promise. For example, to add a delay:
import pRetry from 'p-retry';
import delay from 'delay';
const run = async () => { … };
const result = await pRetry(run, {
onFailedAttempt: async () => {
console.log('Waiting for 1 second before retrying');
await delay(1000);
}
});If the onFailedAttempt function throws, all retries will be aborted and the original promise will reject with the thrown error.
Type: Function
Decide if a retry should occur based on the context. Returning true triggers a retry, false aborts with the error.
It is not called for TypeError (except network errors) and AbortError.
import pRetry from 'p-retry';
const run = async () => { … };
const result = await pRetry(run, {
shouldRetry: ({error, attemptNumber, retriesLeft}) => !(error instanceof CustomError);
});In the example above, the operation will be retried unless the error is an instance of CustomError.
Type: number
Default: 10
The maximum amount of times to retry the operation.
Type: number
Default: 2
The exponential factor to use.
Type: number
Default: 1000
The number of milliseconds before starting the first retry.
Type: number
Default: Infinity
The maximum number of milliseconds between two retries.
Type: boolean
Default: false
Randomizes the timeouts by multiplying with a factor between 1 and 2.
Type: number
Default: Infinity
The maximum time (in milliseconds) that the retried operation is allowed to run.
Type: AbortSignal
You can abort retrying using AbortController.
import pRetry from 'p-retry';
const run = async () => { … };
const controller = new AbortController();
cancelButton.addEventListener('click', () => {
controller.abort(new Error('User clicked cancel button'));
});
try {
await pRetry(run, {signal: controller.signal});
} catch (error) {
console.log(error.message);
//=> 'User clicked cancel button'
}Type: boolean
Default: false
Prevents retry timeouts from keeping the process alive.
Only affects platforms with a .unref() method on timeouts, such as Node.js.
Wrap a function so that each call is automatically retried on failure.
import {makeRetriable} from 'p-retry';
const fetchWithRetry = makeRetriable(fetch, {retries: 5});
const response = await fetchWithRetry('https://sindresorhus.com/unicorn');Abort retrying and reject the promise.
Type: string
An error message.
Type: Error
A custom error.
You can pass arguments to the function being retried by wrapping it in an inline arrow function:
import pRetry from 'p-retry';
const run = async emoji => {
// …
};
// Without arguments
await pRetry(run, {retries: 5});
// With arguments
await pRetry(() => run('🦄'), {retries: 5});The package uses setTimeout and clearTimeout from the global scope, so you can use the Node.js test timer mocking or a package like sinon.
Use an AbortController to signal cancellation on SIGINT, and pass its signal to pRetry:
import pRetry from 'p-retry';
const controller = new AbortController();
process.once('SIGINT', () => {
controller.abort(new Error('SIGINT received'));
});
try {
await pRetry(run, {signal: controller.signal});
} catch (error) {
console.log('Retry stopped due to:', error.message);
}The package does not handle process signals itself to avoid global side effects.
