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1# p-retry [![Build Status](https://travis-ci.org/sindresorhus/p-retry.svg?branch=master)](https://travis-ci.org/sindresorhus/p-retry)
2
3> Retry a promise-returning or async function
4
5It does exponential backoff and supports custom retry strategies for failed operations.
6
7
8## Install
9
10```
11$ npm install p-retry
12```
13
14
15## Usage
16
17```js
18const pRetry = require('p-retry');
19const fetch = require('node-fetch');
20
21const run = async () => {
22 const response = await fetch('https://sindresorhus.com/unicorn');
23
24 // Abort retrying if the resource doesn't exist
25 if (response.status === 404) {
26 throw new pRetry.AbortError(response.statusText);
27 }
28
29 return response.blob();
30};
31
32(async () => {
33 console.log(await pRetry(run, {retries: 5}));
34})();
35```
36
37With the `onFailedAttempt` option:
38
39```js
40const run = async () => {
41 const response = await fetch('https://sindresorhus.com/unicorn');
42
43 if (response.status !== 200) {
44 throw new Error(response.statusText);
45 }
46
47 return response.json();
48};
49
50(async () => {
51 const result = await pRetry(run, {
52 onFailedAttempt: error => {
53 console.log(`Attempt ${error.attemptNumber} failed. There are ${error.retriesLeft} retries left.`);
54 // 1st request => Attempt 1 failed. There are 4 retries left.
55 // 2nd request => Attempt 2 failed. There are 3 retries left.
56 // …
57 },
58 retries: 5
59 });
60
61 console.log(result);
62})();
63```
64
65
66## API
67
68### pRetry(input, [options])
69
70Returns 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.
71
72It doesn't retry on `TypeError` as that's a user error.
73
74#### input
75
76Type: `Function`
77
78Receives the number of attempts as the first argument and is expected to return a `Promise` or any value.
79
80#### options
81
82Type: `Object`
83
84Options are passed to the [`retry`](https://github.com/tim-kos/node-retry#retryoperationoptions) module.
85
86##### onFailedAttempt(error)
87
88Type: `Function`
89
90Callback 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.
91
92### pRetry.AbortError(message|error)
93
94Abort retrying and reject the promise.
95
96### message
97
98Type: `string`
99
100Error message.
101
102### error
103
104Type: `Error`
105
106Custom error.
107
108
109## Tip
110
111You can pass arguments to the function being retried by wrapping it in an inline arrow function:
112
113```js
114const pRetry = require('p-retry');
115
116const run = async emoji => {
117 // …
118};
119
120(async () => {
121 // Without arguments
122 await pRetry(run, {retries: 5});
123
124 // With arguments
125 await pRetry(() => run('🦄'), {retries: 5});
126})();
127```
128
129
130## Related
131
132- [p-timeout](https://github.com/sindresorhus/p-timeout) - Timeout a promise after a specified amount of time
133- [More…](https://github.com/sindresorhus/promise-fun)
134
135
136## License
137
138MIT © [Sindre Sorhus](https://sindresorhus.com)
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