# Promise Retry
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Abstraction for exponential and custom retry strategies to failed promises.

Retrying made simple and easy. \o/

## Installation

Using yarn:
```js
yarn add promise-fn-retry
```

Using npm:

```js
npm i --save promise-fn-retry
```

## Usage

Simple Request

```js
  import fetch from 'node-fetch';
  import retry from 'promise-fn-retry';

  const requestUser = () => {
    // Create a function that return a promise
    const promiseFn = () => fetch('https://api.github.com/users/14');

    // call retry passing promiseFn argument. Thats it!
    return retry(promiseFn)
      .then(res => res.json());
  };

  export default requestUser;

```

Using options param

```js
  import fetch from 'node-fetch';
  import retry from 'promise-fn-retry';

  const requestUser = () => {
    // Create a function that return a promise
    const promiseFn = () => fetch('https://api.github.com/users/14');

    // You can use options to your retry rules strategy.
    const options = {
      times: 3,
      initialDelay: 100,
    };

    // call retry passing promiseFn argument. Thats it!
    return retry(promiseFn, options)
      .then(res => res.json());
  };

  export default requestUser;

```


## API

```js
  retry(promiseFn : Function, [options : Object]) => Promise
```

### Options

These are the available config options for retrying. Only promiseFn is required. If an object isn't provided, the lib will use the default options.

```javascript
{
  // The number of times the lib will retry execute the promiseFn
  // Default: 1
  times: 3,

  // The first wait time to delay
  // Default: 100
  initialDelayTime: 200,

  // (Optional) This callback is executed on each retry. It's useful to log your errors to a log service for example
  // Default: null
  onRetry: (error) => {
    console.log(error);
    sendToSentry(error);
    sendToKibana(error);
  },

 // (Optional) This callback is executed before each retry to determine if it's necessary retrying.
 // If the function returns true, the next retry will be executed, else the retrying will be canceled.
 // Default: null
 shouldRetry: (error) => {
   console.log(error);
   return (error.message === 'FAILED_AUTH');
 }
}
```

### Delay strategy

Each retry doubles the current delay.

- The first delay uses the `initialDelayTime` option, like `100ms`.
- The second uses `200ms` (100 * 2).
- The third uses `400ms` ...


## License

Licensed under the MIT License, Copyright © 2018-present Felippe Maurício.