| 1 | 'use strict' |
| 2 | const FixedThreadPool = require('./fixed') |
| 3 | |
| 4 | /** |
| 5 | * A thread pool with a min/max number of threads , is possible to execute tasks in sync or async mode as you prefer. <br> |
| 6 | * This thread pool will create new workers when the other ones are busy, until the max number of threads, |
| 7 | * when the max number of threads is reached, an exception will be thrown. |
| 8 | * This pool will select the worker thread in a round robin fashion. <br> |
| 9 | * @author Alessandro Pio Ardizio |
| 10 | * @since 0.0.1 |
| 11 | */ |
| 12 | class DynamicThreadPool extends FixedThreadPool { |
| 13 | /** |
| 14 | * |
| 15 | * @param {Number} min Min number of threads that will be always active |
| 16 | * @param {Number} max Max number of threads that will be active |
| 17 | * @param {Object} an object with possible options for example maxConcurrency |
| 18 | */ |
| 19 | constructor (min, max, filename, opts) { |
| 20 | super(min, filename, opts) |
| 21 | this.max = max |
| 22 | } |
| 23 | |
| 24 | _chooseWorker () { |
| 25 | let worker |
| 26 | for (const entry of this.tasks) { |
| 27 | if (entry[1] === 0) { |
| 28 | worker = entry[0] |
| 29 | break |
| 30 | } |
| 31 | } |
| 32 | |
| 33 | if (worker) { |
| 34 | // a worker is free, use it |
| 35 | return worker |
| 36 | } else { |
| 37 | if (this.workers.length === this.max) { |
| 38 | throw new Error('Max number of threads reached !!!') |
| 39 | } |
| 40 | // all workers are busy create a new worker |
| 41 | const worker = this._newWorker() |
| 42 | worker.port2.on('message', (message) => { |
| 43 | if (message.kill) { |
| 44 | worker.postMessage({ kill: 1 }) |
| 45 | worker.terminate() |
| 46 | } |
| 47 | }) |
| 48 | return worker |
| 49 | } |
| 50 | } |
| 51 | } |
| 52 | |
| 53 | module.exports = DynamicThreadPool |