src/dynamic.ts

   1 import FixedThreadPool, {
   2   FixedThreadPoolOptions,
   3   WorkerWithMessageChannel
   4 } from './fixed'
   5
   6 import { EventEmitter } from 'events'
   7
   8 class MyEmitter extends EventEmitter {}
   9
  10 export type DynamicThreadPoolOptions = FixedThreadPoolOptions
  11
  12 /**
  13  * A thread pool with a min/max number of threads, is possible to execute tasks in sync or async mode as you prefer.
  14  *
  15  * This thread pool will create new workers when the other ones are busy, until the max number of threads,
  16  * when the max number of threads is reached, an event will be emitted, if you want to listen this event use the emitter method.
  17  *
  18  * @author [Alessandro Pio Ardizio](https://github.com/pioardi)
  19  * @since 0.0.1
  20  */
  21 export default class DynamicThreadPool<
  22   Data = any,
  23   Response = any
  24 > extends FixedThreadPool<Data, Response> {
  25   public readonly emitter: MyEmitter
  26
  27   /**
  28    * @param min Min number of threads that will be always active
  29    * @param max Max number of threads that will be active
  30    * @param filename A file path with implementation of `ThreadWorker` class, relative path is fine.
  31    * @param opts An object with possible options for example `errorHandler`, `onlineHandler`. Default: `{ maxTasks: 1000 }`
  32    */
  33   public constructor (
  34     public readonly min: number,
  35     public readonly max: number,
  36     public readonly filename: string,
  37     public readonly opts: DynamicThreadPoolOptions = { maxTasks: 1000 }
  38   ) {
  39     super(min, filename, opts)
  40
  41     this.emitter = new MyEmitter()
  42   }
  43
  44   protected _chooseWorker (): WorkerWithMessageChannel {
  45     let worker: WorkerWithMessageChannel
  46     for (const entry of this.tasks) {
  47       if (entry[1] === 0) {
  48         worker = entry[0]
  49         break
  50       }
  51     }
  52
  53     if (worker) {
  54       // a worker is free, use it
  55       return worker
  56     } else {
  57       if (this.workers.length === this.max) {
  58         this.emitter.emit('FullPool')
  59         return super._chooseWorker()
  60       }
  61       // all workers are busy create a new worker
  62       const worker = this._newWorker()
  63       worker.port2.on('message', (message) => {
  64         if (message.kill) {
  65           worker.postMessage({ kill: 1 })
  66           worker.terminate()
  67           // clean workers from data structures
  68           const workerIndex = this.workers.indexOf(worker)
  69           this.workers.splice(workerIndex, 1)
  70           this.tasks.delete(worker)
  71         }
  72       })
  73       return worker
  74     }
  75   }
  76 }
  77
  78 module.exports = DynamicThreadPool