JarCastingp-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.
It doesn't retry on TypeError as that's a user error.
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.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);
})();
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});
})();