| 1 | 'use strict' |
| 2 | const FixedThreadPool = require('./fixed') |
| 3 | const { randomWorker } = require('./util') |
| 4 | const EventEmitter = require('events') |
| 5 | class MyEmitter extends EventEmitter {} |
| 6 | |
| 7 | /** |
| 8 | * A thread pool with a min/max number of threads , is possible to execute tasks in sync or async mode as you prefer. <br> |
| 9 | * This thread pool will create new workers when the other ones are busy, until the max number of threads, |
| 10 | * when the max number of threads is reached, an event will be emitted , if you want to listen this event use the emitter method. |
| 11 | * @author Alessandro Pio Ardizio |
| 12 | * @since 0.0.1 |
| 13 | */ |
| 14 | class DynamicThreadPool extends FixedThreadPool { |
| 15 | /** |
| 16 | * |
| 17 | * @param {Number} min Min number of threads that will be always active |
| 18 | * @param {Number} max Max number of threads that will be active |
| 19 | * @param {Object} an object with possible options for example maxConcurrency |
| 20 | */ |
| 21 | constructor (min, max, filename, opts) { |
| 22 | super(min, filename, opts) |
| 23 | this.max = max |
| 24 | this.emitter = new MyEmitter() |
| 25 | } |
| 26 | |
| 27 | /** |
| 28 | * Return an event emitter that will send some messages, for example |
| 29 | * a message will be sent when max number of threads is reached and all threads are busy |
| 30 | * in this case it will emit a message |
| 31 | */ |
| 32 | emitter () { |
| 33 | return this.emitter |
| 34 | } |
| 35 | |
| 36 | _chooseWorker () { |
| 37 | let worker |
| 38 | for (const entry of this.tasks) { |
| 39 | if (entry[1] === 0) { |
| 40 | worker = entry[0] |
| 41 | break |
| 42 | } |
| 43 | } |
| 44 | |
| 45 | if (worker) { |
| 46 | // a worker is free, use it |
| 47 | return worker |
| 48 | } else { |
| 49 | if (this.workers.length === this.max) { |
| 50 | this.emitter.emit('FullPool') |
| 51 | return randomWorker(this.tasks) |
| 52 | } |
| 53 | // all workers are busy create a new worker |
| 54 | const worker = this._newWorker() |
| 55 | worker.port2.on('message', (message) => { |
| 56 | if (message.kill) { |
| 57 | worker.postMessage({ kill: 1 }) |
| 58 | worker.terminate() |
| 59 | } |
| 60 | }) |
| 61 | return worker |
| 62 | } |
| 63 | } |
| 64 | } |
| 65 | |
| 66 | module.exports = DynamicThreadPool |