Exponential retry backoff library offering full jitter and decorators.
This modules allows retrying an asynchronous call, backing off exponentially.
Optionally, full jitter can be added to the backoff time, as explained in this
AWS article. The
functionality is accessible directly through a function call, or using ES2016
decorators.
``
npm install --save backoff-decorator
`javascript
const Backoff = require("../src/backoff");
const request = require("request-promise");
// an error class used to determine when to retry
class NotNowError extends Error {}
// this function simulates an async call that fails
// 9 times than succeeds on the 10th call.
let trials = 0;
function get(url) {
trials++;
console.log(new Date());
if (trials % 10 === 0) {
console.log('fetching', url);
return request.get(url);
}
else {
return Promise.reject(new NotNowError());
}
}
// this are the options to the backoff call
const backoffOptions = {
maxRetries: 10, // do not retry more than this amount of times
maxDelayMs: 1000, // cap the exponential backoff to this value
backoffFactor: 100, // the backoff factor
predicate: (err) => err instanceof NotNowError, // determines when to retry
fullJitter: false, // do not add random jitter
};
// call the 'get' function with retries.
// the arguments following the function itself are the same as bind()
Backoff.retry(backoffOptions, get, this, 'http://unito.io');
`
This example uses TypeScript to allow the use of decorators.
`js
import { backoff } from '../src/backoff';
import * as request from 'request-promise';
class NotNowError extends Error {}
class UnsureCaller {
private trials = 0;
async get(url: string): Promise
this.trials++;
console.log(new Date());
if (this.trials % 10 === 0) {
console.log('fetching', url);
return request.get(url);
} else {
throw new NotNowError();
}
}
}
class Fetcher {
backoffOptions = {
maxRetries: 10,
maxDelayMs: 1000,
backoffFactor: 100,
predicate: (err: Error) => err instanceof NotNowError,
fullJitter: false,
};
private caller = new UnsureCaller();
@backoff
async fetchUrl(url: string): Promise
return this.caller.get(url);
}
}
const fetcher = new Fetcher();
fetcher.fetchUrl('http://unito.io');
``
MIT