src/dynamic.ts

   1 /* eslint-disable @typescript-eslint/strict-boolean-expressions */
   2
   3 import {
   4   FixedThreadPool,
   5   FixedThreadPoolOptions,
   6   WorkerWithMessageChannel
   7 } from './fixed'
   8
   9 import { EventEmitter } from 'events'
  10
  11 class MyEmitter extends EventEmitter {}
  12
  13 export type DynamicThreadPoolOptions = FixedThreadPoolOptions
  14
  15 /**
  16  * A thread pool with a min/max number of threads, is possible to execute tasks in sync or async mode as you prefer.
  17  *
  18  * This thread pool will create new workers when the other ones are busy, until the max number of threads,
  19  * when the max number of threads is reached, an event will be emitted, if you want to listen this event use the emitter method.
  20  *
  21  * @author [Alessandro Pio Ardizio](https://github.com/pioardi)
  22  * @since 0.0.1
  23  */
  24 export class DynamicThreadPool<
  25   Data = any,
  26   Response = any
  27 > extends FixedThreadPool<Data, Response> {
  28   public readonly emitter: MyEmitter
  29
  30   /**
  31    * @param min Min number of threads that will be always active
  32    * @param max Max number of threads that will be active
  33    * @param filename A file path with implementation of `ThreadWorker` class, relative path is fine.
  34    * @param opts An object with possible options for example `errorHandler`, `onlineHandler`. Default: `{ maxTasks: 1000 }`
  35    */
  36   public constructor (
  37     public readonly min: number,
  38     public readonly max: number,
  39     public readonly filename: string,
  40     public readonly opts: DynamicThreadPoolOptions = { maxTasks: 1000 }
  41   ) {
  42     super(min, filename, opts)
  43
  44     this.emitter = new MyEmitter()
  45   }
  46
  47   protected chooseWorker (): WorkerWithMessageChannel {
  48     let worker: WorkerWithMessageChannel | undefined
  49     for (const entry of this.tasks) {
  50       if (entry[1] === 0) {
  51         worker = entry[0]
  52         break
  53       }
  54     }
  55
  56     if (worker) {
  57       // a worker is free, use it
  58       return worker
  59     } else {
  60       if (this.workers.length === this.max) {
  61         this.emitter.emit('FullPool')
  62         return super.chooseWorker()
  63       }
  64       // all workers are busy create a new worker
  65       const worker = this.newWorker()
  66       worker.port2?.on('message', (message: { kill?: number }) => {
  67         if (message.kill) {
  68           worker.postMessage({ kill: 1 })
  69           // eslint-disable-next-line no-void
  70           void worker.terminate()
  71           // clean workers from data structures
  72           const workerIndex = this.workers.indexOf(worker)
  73           this.workers.splice(workerIndex, 1)
  74           this.tasks.delete(worker)
  75         }
  76       })
  77       return worker
  78     }
  79   }
  80 }