@pxtrn/async-backoff

Backoff failing async calls until they successfully complete. Usefull for recoverable errors that most likely go away on retry. For example errors like ENOTFOUND, EHOSTUNREACH etc. on network calls or EBUSY on file system calls.

Installation

npm install --save @pxtrn/async-backoff

Usage

Javascript

const { backoff } = require('@pxtrn/async-backoff');

let counter = 1;

async function request() {
  console.log(`request number: ${counter}`);

  if(counter < 5) {
    counter ++;
    throw new Error('Some Network error');
  }

  console.log(`successfully requestd resource`);
  return true;
}


(async function() {
  try {
    const result = await backoff(request, {maxAttempts: 5, retryTimeout: 100});
  } catch(err) {
    console.error(`Could not request resource`);
  }
})();

Typescript

import { backoff } from '@pxtrn/async-backoff';

let counter = 1;

interface IUser {name: string; email: string};

async function request(): Promise<IUser> {
  console.log(`request number: ${counter}`);

  if(counter < 5) {
    counter ++;
    throw new Error('Some Network error');
  }

  console.log(`successfully requestd resource`);
  return {name: 'Bob', email: '[e-mail]'};
}


(async function() {
  try {
    const result = await backoff<IUser>(request, {maxAttempts: 5, retryTimeout: 100});
    console.log('Got result', result);
  } catch(err) {
    console.error(`Could not request resource`);
  }
})();

Parameters

• fn {async Function} Async function to await
• options {Object}
  • maxAttempts: {Integer} Max number of function calls
  • retryTimeout: {Integer} ms to wait. Only for default delayStrategy (return attempts * retryTimeout)
  • retryStrategy: {Function(err)} return boolean true if another call to fn should be tryed, even maxAttempts has not been reached yet
  • delayStrategy: {Function(attempts)} return an integer in ms for which the next attempt should be delayed
  • signal: {AbortSignal}

Custom retry strategy

await backoff(request, {
  maxAttempts: 5,
  retryStrategy: (err) => {
    const retryErrors = ['ECONNRESET', 'ENOTFOUND', 'ESOCKETTIMEDOUT'];
    return retryErrors.includes(err.code);
  }
});

Custom delay strategy

await backoff(request, {
  maxAttempts: 5,
  delayStrategy: (attempts) => {
    return Math.min((Math.pow(2, attempts) * 100), 5e3);
  }
});

Aborting a running backoff

Note this does only abort the backoff itself, not the async function passed.

const ac = new AbortController();
setTimeout(() => ac.abort(), 2e3);


await backoff(request, {
  signal: ac.signal
});