149 lines
3.5 KiB
Markdown
149 lines
3.5 KiB
Markdown
# p-retry
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> Retry a promise-returning or async function
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It does exponential backoff and supports custom retry strategies for failed operations.
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## Install
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```
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$ npm install p-retry
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```
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## Usage
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```js
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const pRetry = require('p-retry');
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const fetch = require('node-fetch');
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const run = async () => {
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const response = await fetch('https://sindresorhus.com/unicorn');
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// Abort retrying if the resource doesn't exist
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if (response.status === 404) {
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throw new pRetry.AbortError(response.statusText);
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}
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return response.blob();
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};
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(async () => {
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console.log(await pRetry(run, {retries: 5}));
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})();
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```
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## API
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### pRetry(input, options?)
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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.
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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](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#Checking_that_the_fetch_was_successful) to indicate this. See [whatwg/fetch#526 (comment)](https://github.com/whatwg/fetch/issues/526#issuecomment-554604080)
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#### input
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Type: `Function`
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Receives the current attempt number as the first argument and is expected to return a `Promise` or any value.
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#### options
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Type: `object`
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Options are passed to the [`retry`](https://github.com/tim-kos/node-retry#retryoperationoptions) module.
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##### onFailedAttempt(error)
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Type: `Function`
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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.
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```js
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const run = async () => {
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const response = await fetch('https://sindresorhus.com/unicorn');
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if (!response.ok) {
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throw new Error(response.statusText);
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}
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return response.json();
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};
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(async () => {
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const result = await pRetry(run, {
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onFailedAttempt: error => {
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console.log(`Attempt ${error.attemptNumber} failed. There are ${error.retriesLeft} retries left.`);
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// 1st request => Attempt 1 failed. There are 4 retries left.
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// 2nd request => Attempt 2 failed. There are 3 retries left.
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// …
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},
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retries: 5
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});
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console.log(result);
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})();
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```
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The `onFailedAttempt` function can return a promise. For example, you can do some async logging:
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```js
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const pRetry = require('p-retry');
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const logger = require('./some-logger');
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const run = async () => { … };
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(async () => {
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const result = await pRetry(run, {
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onFailedAttempt: async error => {
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await logger.log(error);
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}
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});
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})();
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```
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If the `onFailedAttempt` function throws, all retries will be aborted and the original promise will reject with the thrown error.
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### pRetry.AbortError(message)
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### pRetry.AbortError(error)
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Abort retrying and reject the promise.
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### message
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Type: `string`
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Error message.
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### error
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Type: `Error`
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Custom error.
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## Tip
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You can pass arguments to the function being retried by wrapping it in an inline arrow function:
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```js
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const pRetry = require('p-retry');
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const run = async emoji => {
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// …
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};
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(async () => {
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// Without arguments
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await pRetry(run, {retries: 5});
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// With arguments
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await pRetry(() => run('🦄'), {retries: 5});
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})();
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```
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## Related
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- [p-timeout](https://github.com/sindresorhus/p-timeout) - Timeout a promise after a specified amount of time
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- [More…](https://github.com/sindresorhus/promise-fun)
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