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# exponential-backoff | |
A utility that allows retrying a function with an exponential delay between attempts. | |
## Installation | |
``` | |
npm i exponential-backoff | |
``` | |
## Usage | |
The `backOff<T>` function takes a promise-returning function to retry, and an optional `BackOffOptions` object. It returns a `Promise<T>`. | |
```ts | |
function backOff<T>( | |
request: () => Promise<T>, | |
options?: BackOffOptions | |
): Promise<T>; | |
``` | |
Here is an example retrying a function that calls a hypothetical weather endpoint: | |
```js | |
import { backOff } from "exponential-backoff"; | |
function getWeather() { | |
return fetch("weather-endpoint"); | |
} | |
async function main() { | |
try { | |
const response = await backOff(() => getWeather()); | |
// process response | |
} catch (e) { | |
// handle error | |
} | |
} | |
main(); | |
``` | |
Migrating across major versions? Here are our [breaking changes](https://github.com/coveo/exponential-backoff/tree/master/doc/migration-guide.md). | |
### `BackOffOptions` | |
- `delayFirstAttempt?: boolean` | |
Decides whether the `startingDelay` should be applied before the first call. If `false`, the first call will occur without a delay. | |
Default value is `false`. | |
- `jitter?: JitterType | string` | |
Decides whether a [jitter](https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/) should be applied to the delay. Possible values are `full` and `none`. | |
Default value is `none`. | |
- `maxDelay?: number` | |
The maximum delay, in milliseconds, between two consecutive attempts. | |
Default value is `Infinity`. | |
- `numOfAttempts?: number` | |
The maximum number of times to attempt the function. | |
Default value is `10`. | |
Minimum value is `1`. | |
- `retry?: (e: any, attemptNumber: number) => boolean | Promise<boolean>` | |
The `retry` function can be used to run logic after every failed attempt (e.g. logging a message, assessing the last error, etc.). It is called with the last error and the upcoming attempt number. Returning `true` will retry the function as long as the `numOfAttempts` has not been exceeded. Returning `false` will end the execution. | |
Default value is a function that always returns `true`. | |
- `startingDelay?: number` | |
The delay, in milliseconds, before executing the function for the first time. | |
Default value is `100` ms. | |
- `timeMultiple?: number` | |
The `startingDelay` is multiplied by the `timeMultiple` to increase the delay between reattempts. | |
Default value is `2`. | |