retryee

retryee is a programmable library for retry. This is written in TypeScript. It enables developers to customize retry & backoff in a simple way. With retryee, you can specify how many times to retry, how long to wait between retries, and what errors to catch in a programable way.

Installation

To install retryee, run:

npm install retryee

Usage

Here's an simplest example of using retryee with fetch:

Basic Example

import { retryee, exponentialBackoff } from 'retryee'

// - retry 5 times
// - with exponentialBackoff (0sec -> 1000ms -> 2000ms -> 4000ms -> 8000ms)
// - retry if response returns 5xx Error
const fetchWithRetry = async (url: string) => {
  return await retryee(5, () => fetch(url))
    .if((response) => response.status >= 500)
    .backoff(exponentialBackoff(1000))
    .run()
}

Customize Backoff

If you want to customize backoff, you can write code like:

import { retryee } from 'retryee'

// retry 5 times
// with custom backoff(count * 100, that is 0ms -> 2000ms -> 4000ms -> 6000ms -> 8000ms)
const fetchWithRetry = async (url: string) => {
  return await retryee(5, () => fetch(url))
    .if((result) => result.status >= 500)
    .backoff((count) => count * 2000)
    .run()
}

const fetchWithRetry = async (url: string) => {
  return await retryee(5, () => fetch(url))
    .if((result) => result.status >= 500)
    .backoff((count) => count * 2000)
    .run()
}

Catch Exception

If you want to catch exception, you can write code like this:

// - retry if it throws error OR response returns 5xx Error.
const fetchWithRetry = async (url: string) => {
  return await retryee(5, async () => {
    try {
      const result = await fetch(url)
      return result;
    } catch (e) {
      if (e instanceof Error) return e
      if (typeof e === 'string') return new Error(e)
      return new Error(`Unknown Error: ${e}`)
    }
  )
  .if((result) => {
    if (result instanceof Error) return true;
    if (result?.status >= 500) return true;
    return false;
  })
  .backoff(exponentialBackoff(1000))
  .run()
}