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