@chris.troutner/retry-queue

retry-queue

This library is based on p-queue and p-retry. It create a Queue for executing Promise-based functions. If the function fails, it will be automatically retried.

Executing promise-based functions and then needed to do an automatic retry if it fails, is an extremely common scenario is the software I write. I created this small library because I got tired of constantly re-writing this functionality.

This repository is forked from npm-lib-boilerplate-esm.

Installation

• npm install --save-exact @chris.troutner/retry-queue

Environment

• node.js v16+

Example

This provides a simple example of how to use this retry queue.

longRunningProcess() is a Promise-based function. It lasts for 2-5 seconds and it has a 25% chance of failing.

A new longRunningProcess() is added to the queue as soon as the previous one completes. Awaiting on the queue will wait until the queue is empty before adding a new task. If the await is omitted, all processes will be added immediately and the Queue is allowed to work according concurrency setting.

// Include the library.
import RetryQueue from '@chris.troutner/retry-queue'

// Retry-Queue settings:
const options = {
  concurrency: 1,
  attempts: 5,
  retryPeriod: 1000
}
const retryQueue = new RetryQueue(options)

// Example function using the retry-queue.
async function retryQueueExample () {
  try {
    // Generate 10 processes.
    const processCount = 10
    for (let i = 0; i < processCount; i++) {
      // Dummy data to pass to the function.
      const now = new Date()
      const processObj = {
        index: i,
        startedOn: now.toLocaleString()
      }

      // Add the process to the queue.
      // Omit the await to load up the queue quickly and allow its internal
      // concurrency logic to drive execution.
      await retryQueue.addToQueue(longRunningProcess, processObj)
    }
  } catch (err) {
    console.error('Error in retryQueueExample(): ', err)
  }
}
retryQueueExample()

// A long-running, Promise-based function
// It will run between 2-5 seconds.
// It has a 25% chance of throwing an error.
async function longRunningProcess (inObj = {}) {
  // Wait for 2 seconds.
  await retryQueue.sleep(2000)

  const rndNum1 = Math.random()
  const rndNum2 = 3 * Math.random()

  // 25% chance of failing
  if (rndNum1 < 0.25) throw new Error('longRunningProcess() failed')

  // Wait an additional 0-3 seconds
  await retryQueue.sleep(rndNum2)

  // Add a timestamp for when the process completed.
  const now = new Date()
  inObj.stoppedOn = now.toLocaleString()

  console.log(`longRunningProcess() ${inObj.index+1} completed with input object ${JSON.stringify(inObj, null, 2)}`)

  return true
}

The above code will produce an output like this:

Attempt 1 of 5 failed. Waiting before trying again.
Waiting 1000 milliseconds before trying again.

Attempt 2 of 4 failed. Waiting before trying again.
Waiting 1000 milliseconds before trying again.

longRunningProcess() 1 completed with input object {
  "index": 0,
  "startedOn": "9/15/2022, 1:31:35 PM",
  "stoppedOn": "9/15/2022, 1:31:47 PM"
}
longRunningProcess() 2 completed with input object {
  "index": 1,
  "startedOn": "9/15/2022, 1:31:47 PM",
  "stoppedOn": "9/15/2022, 1:31:49 PM"
}
longRunningProcess() 3 completed with input object {
  "index": 2,
  "startedOn": "9/15/2022, 1:31:49 PM",
  "stoppedOn": "9/15/2022, 1:31:51 PM"
}
longRunningProcess() 4 completed with input object {
  "index": 3,
  "startedOn": "9/15/2022, 1:31:51 PM",
  "stoppedOn": "9/15/2022, 1:31:53 PM"
}
longRunningProcess() 5 completed with input object {
  "index": 4,
  "startedOn": "9/15/2022, 1:31:53 PM",
  "stoppedOn": "9/15/2022, 1:31:55 PM"
}
longRunningProcess() 6 completed with input object {
  "index": 5,
  "startedOn": "9/15/2022, 1:31:55 PM",
  "stoppedOn": "9/15/2022, 1:31:57 PM"
}
longRunningProcess() 7 completed with input object {
  "index": 6,
  "startedOn": "9/15/2022, 1:31:57 PM",
  "stoppedOn": "9/15/2022, 1:31:59 PM"
}
Attempt 1 of 5 failed. Waiting before trying again.
Waiting 1000 milliseconds before trying again.

Attempt 2 of 4 failed. Waiting before trying again.
Waiting 1000 milliseconds before trying again.

longRunningProcess() 8 completed with input object {
  "index": 7,
  "startedOn": "9/15/2022, 1:31:59 PM",
  "stoppedOn": "9/15/2022, 1:32:10 PM"
}
longRunningProcess() 9 completed with input object {
  "index": 8,
  "startedOn": "9/15/2022, 1:32:10 PM",
  "stoppedOn": "9/15/2022, 1:32:12 PM"
}
longRunningProcess() 10 completed with input object {
  "index": 9,
  "startedOn": "9/15/2022, 1:32:12 PM",
  "stoppedOn": "9/15/2022, 1:32:14 PM"
}

Licence

MIT