Purpose

Minimalist, efficient and performance focused retry system.
Basically it helps developer to retry a function with a specific interval, exponential factor etc.

No dependency.

Compatibility

/!\ This module use async/await syntax, this is why you must have node 7.6+.

Supported and tested : >= 7.6

| Version | Supported | Tested |
| ------------- |:-------------:|:--------------:|
| 20.x | yes | yes |
| 18.x | yes | yes |
| 16.x | yes | yes |
| 14.x | yes | yes |
| 12.x | no | yes |
| 10.x | no | yes |
| 9.x | no | yes |
| 8.x | no | yes |
| >= 7.6 | no | yes |

Installation

``console
$ npm install async-await-retry --save
`

Usage

Basic usage


`javascript
const retry = require('async-await-retry');

const func = async () => {return new Promise((resolve) => resolve('OK'))};

try {
const res = await retry(func)
} catch (err) {
console.log('The function execution failed !')
}
`

Sync function syntax


`javascript
const retry = require('async-await-retry');

const func = () => {...};

try {
const res = await retry(func)
console.log(res) // output : OK
} catch (err) {
console.log('The function execution failed !')
}
`

Anonymous function style


`javascript
const retry = require('async-await-retry');

try {
const res = await retry(async () => {
return new Promise((resolve) => resolve('OK'))
})

console.log(res) // output : OK
} catch (err) {
console.log('The function execution failed !')
}
`

Callback function style


`javascript
const retry = require('async-await-retry');

try {
const res = await retry((arg1, cb) => {
....
cb(err, data); // send err as first argument
}, ["arg1"], {isCb: true});
} catch (err) {
console.log('The function execution failed !')
}
`

Options

## retry(function, [args], [config])

* function : function to retry in case of error
* args : your function's parameters in case you don't use callback style
* config : an object containing all retry process options

options

| Option | description | Default value |
| --------------- |:------------------------------------------------:|:----------------:|
| retriesMax | Maximum number of retries | 3 |
| interval | Delay in ms between two tentatives | 0 |
| exponential | Will the interval increase exponentially ? | true |
| maxBackoff | Maximum delay before to retry (with exponential) | 30s |
| factor | The exponential factor to use | 2 |
| jitter | Random jitter in ms to add to the interval | 0 |
| isCb | Old callback function style ? | false |
| onAttemptFail | User's callback to manage retry system | default fallback |


An example of custom options :
`javascript
const retry = require('async-await-retry');

try {
const res = await retry(async () => {
return new Promise((resolve) => resolve('OK'))
}, null, {retriesMax: 4, interval: 100, exponential: true, factor: 3, jitter: 100})

console.log(res) // output : OK
} catch (err) {
console.log('The function execution failed !')
}
`

onAttemptFail

This method can be used to manage, by yourself, the retry system.
It's called when an error occurred and before to retry.
This method can have three behaviors:
- you can throw an error
- if it returns truthy value then normal retry system continues
- if it returns falsy value then the retry system stop

`javascript
const retry = require('async-await-retry');

try {
const res = await retry(MyfuncToRetry, null, {
onAttemptFail: (data) => {
// do some stuff here, like logging errors
}
});
} catch (err) {
console.log('The function execution failed !')
}
`

The data argument is an object that can be described like this:

| Property | description |
| --------------- |:------------------------------------------:|
| error | The current error object |
| currentRetry | The current retry value |
| retriesMax | Maximum number of retries |
| interval | Delay in ms between two tentatives |
| exponential | Will the interval increase exponentially ? |
| factor | The exponential factor to use |
| jitter | Random jitter in ms to add to the interval |
| maxBackoff | Maximum delay before to retry |

Test

`console
$ npm test
``

Coverage report can be found in coverage/.