rolly-retry

A retry, failover library with types.

State

Motivation

1. I needed a way to call a function n times until the call succeeds.
2. I needed to be able to define a successful call.
3. I wanted to try calling 1 or more different functions until one succeeded.

Usage

retry one async function

import { retry } from "rolly-retry";

/**
* call retriable_func("value")
* until the result === "success"
* up to 4 times
*/
await retry(
  async () => await retriable_func("value"), 
  (result) => result === "success",
  4
);

retry and failover

import { retry } from "rolly-retry";

/**
* call primary_retriable()
* until the result === "success"
* up to 4 times
* otherwise, call backup_retriable()
* until the result === "success"
* up to 4 times
*/
await retry(
  [
    async () => await primary_retriable(),
    async () => await backup_retriable(),
  ],
  (result) => result === "success",
  4
);

retrying with backoff

You can pass a back off to the retry. The back off will cause a delay after the first retry. Backoffs reset for each function.

import { retry } from "rolly-retry";

await retry(
  [
    async () => await func_i_want_to_try(1)
  ], 
  (result) => false,
  3,
  { 
    constant: 10, // constant 10ms delay after first try
    linear: 20    // linear X20ms delay after first try
  }
);
expect(calls).toBe(3);
/**      
 * Call  Constant  Linear  Delay TotalMs
 * 0:    0         0       0     0
 * 1:    10        20      30    30
 * 2:    10        40      50    80
*/

synchronous

import { retry } from "rolly-retry";

let value = "";
await retry(() => (value += "a"), (result) => result === "aaa", 4);
expect(value).toBe("aaa");

Install

npm i rolly-retry

Avoid

Unrelated calls

Function calls within a retry(func | [funcs]) operation are essentially synchronous. If you want to asynchronously retry many unrelated functions start multiple retries. e.g.,

import { retry } from "rolly-retry";

const retryOne = retry(funcGroupOne, successOne, 2);
const retryTwo = retry(funcGroupTwo, successTwo, 2);
const allResults = await Promise.allSettled([retryOne, retryTwo]);