paralio

Node.js multithreded executer

Classes

Paralio

The Paralio class is the heart of your application.

import { Paralio } from 'paralio'
import { resolve } from 'path'
 
interface Paralio<Input, Output, Context> {
  max: number // The limit of running processes
  workerPath: string // Path to the worker script
  workers: number // The number of running workers
  input: Input[] // The input data (unchanged)
  output: Output[] // The output array
  _input: Input[] // The consumed input data
  repl: repl.REPLServer // The exposed REPL server
  context: Context // The key-value map passed to every worker
  /*...*/
}
 
const app = new Paralio({
  max: 4, // defaults to the number of cpus
  workerPath: resolve(__dirname, './worker'),
  input: [], // or you can give it a path to a file: resolve(__dirname, 'input.txt')
  onInputLoaded(rawFile: string) {
    /*process the data*/
    return JSON.parse(rawFile)
  }
})
 
/* Called after initializing all of the workers */
app.on('start', self => {/*...*/})
 
/* Called after killing all of the workers */
app.on('end', self => {/*...*/})
 
/* Called when consuming an item */
app.on('consume', ([items_left, consumed_item]) => {/*...*/})

Worker

The class for worker files.

import { Worker } from "paralio"
 
interface Worker<MessageType, Context> {
  context: Context // Context passed from the master
  onMessage(msg: MessageType): Promise<any> | void
}
 
new class extends Worker {
  onMessage(msg) {
    /* It can be either a value or a Promise */
    const output = Process_the_input(msg)
    return output
  }
}()

On using the REPL

Paralio comes a built-in repl to make your (my) life easier. It lets you access the app instance and run some useful commands.

self

You can access the main app instance with the self variable. I.e.: > self.output

.save

Let's you save the output to a specified path (defaults to the cwd).

.rerun

In case you want to rerun your application, here you go!

Motivation

I was basically scraping some information of the wikipedia. It was taking a few minutes to run over just 54 pages. So I thought to myself "What can I do to speed it up?" and the obvious answer came to my mind: multi-threading. The idea itself was brilliant, but I ran into some problems, namely: overloading my cpu with 54 processes... Then I decided to limit the number of processes data at one time and it worked. After that some improvements came to my mind and bada bim, bada boom - Paralio was born.