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Alessandro Pio Ardizio
Alessandro Pio Ardizio

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Nodejs | Thread pool implementations

Node Thread Pool ⏫ 🔛

Nodejs introduced worker_threads module to allow a better use of nodejs for CPU intensive tasks, but there is no official thread pool that allow to reuse threads.

So I develop two thread pool on top on worker_threads that you can use with an high level API .

This project contain two thread pool implementations :

The first implementation is a static thread pool , with a defined number of threads that are started at creation time and will be reused.

The second implementation is a dynamic thread pool with a number of threads started at creation time ( these threads will be always active and reused) and other threads created when the load will increase ( with an upper limit, these threads will be reused when active ), the new created threads will be stopped after a configurable period of inactivity.

You have to implement your worker extending the ThreadWorker class


npm install poolifier --save


You can implement a worker in a simple way , extending the class ThreadWorker :

'use strict'
const { ThreadWorker } = require('poolifier')

function yourFunction (data) {
  // this will be executed in the worker thread,
  // the data will be received by using the execute method
  return { ok: 1 }

class MyWorker extends ThreadWorker {
  constructor () {
    super(yourFunction, { maxInactiveTime: 1000 * 60})
module.exports = new MyWorker()

Instantiate your pool based on your needed :

'use strict'
const { FixedThreadPool, DynamicThreadPool } = require('poolifier')

// a fixed thread pool
const pool = new FixedThreadPool(15,
  { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })

// or a dynamic thread pool
const pool = new DynamicThreadPool(10, 100,
  { errorHandler: (e) => console.error(e), onlineHandler: () => console.log('worker is online') })

pool.emitter.on('FullPool', () => console.log('Pool is full'))

// the execute method signature is the same for both implementations,
// so you can easy switch from one to another
pool.execute({}).then(res => {
}).catch .... 


Performance is one of the main target of these thread pool implementations, we want to have a strong focus on this.

We already have a bench folder where you can find some comparisons.
To choose your pool consider that with a FixedThreadPool or a DynamicThreadPool ( in this case is important the min parameter passed to the constructor) your application memory footprint will increase .

Increasing the memory footprint, your application will be ready to accept more CPU bound tasks, but during idle time your application will consume more memory.

One good choose from my point of view is to profile your application using Fixed/Dynamic thread pool , and to see your application metrics when you increase/decrease the num of threads.

For example you could keep the memory footprint low choosing a DynamicThreadPool with 5 threads, and allow to create new threads until 50/100 when needed, this is the advantage to use the DynamicThreadPool.

But in general , always profile your application


Pull requests, contributors and feedbacks are welcome , join the project :)

Top comments (2)

anandkashyap profile image
Anand Kashyap

Great module & post!!
I am a bit new to benchmarking & profiling. Can you guide me a bit how I could profile a sample function to figure out if fixed or dynamic implementation would be better?

pioardi profile image
Alessandro Pio Ardizio

Hi Anand ,
I would like to help you , you can start from the benchmarks folder into the poolifier repo .
Let me know :)