fixed.js

   1 'use strict'
   2 const {
   3   Worker, isMainThread, MessageChannel
   4 } = require('worker_threads')
   5
   6 console.log('Fixed required')
   7
   8 // FixedThreadPool , TrampolineThreadPool
   9 /**
  10  * A thread pool with a static number of threads , is possible to execute tasks in sync or async mode as you prefer
  11  * @author Alessandro Pio Ardizio
  12  * @since 0.0.1
  13  */
  14 class FixedThreadPool {
  15   /**
  16      *
  17      * @param {Number} numThreads  Num of threads for this worker pool
  18      * @param {Object} an object with possible options for example maxConcurrency
  19      */
  20   constructor (numThreads, task, opts) {
  21     if (!isMainThread) {
  22       throw new Error('Cannot start a thread pool from a worker thread !!!')
  23     }
  24     this.numThreads = numThreads
  25     this.workers = []
  26     this.task = task
  27     for (let i = 1; i <= numThreads; i++) {
  28       const worker = new Worker(__filename)
  29       this.workers.push(worker)
  30       const { port1 } = new MessageChannel()
  31       worker.emitter = port1
  32     }
  33   }
  34
  35   /**
  36    *
  37    * @param {Function} task , a function to execute
  38    * @param {Any} the input for the task specified
  39    */
  40   execute (task, data) {
  41     // TODO select a worker
  42     // configure worker to handle message with the specified task
  43     const idx = chooseWorker(0, this.numThreads - 1)
  44     const worker = this.workers[idx]
  45     const id = generateID()
  46     const res = this._execute(worker, task, id)
  47     worker.emitter.emit(id, data)
  48     return res
  49   }
  50
  51   _execute (worker, task, id) {
  52     return new Promise((resolve, reject) => {
  53       console.log('Executing a task on worker thread ' + worker.threadId)
  54       worker.emitter.once(id, (data) => {
  55         console.log('Receivd a message')
  56         try {
  57           resolve(task(data))
  58         } catch (e) {
  59           reject(e)
  60         }
  61       })
  62     })
  63   }
  64 }
  65
  66 function chooseWorker (min, max) {
  67   min = Math.ceil(min)
  68   max = Math.floor(max)
  69   return Math.floor(Math.random() * (max - min + 1)) + min
  70 }
  71
  72 /**
  73  * Return an id to be associated to a node.
  74  */
  75 const generateID = () => {
  76   return Math.random()
  77     .toString(36)
  78     .substring(7)
  79 }
  80
  81 module.exports = FixedThreadPool