src/worker/WorkerSet.ts

   1 // Partial Copyright Jerome Benoit. 2021. All Rights Reserved.
   2
   3 import { WorkerData, WorkerMessageEvents, WorkerOptions, WorkerSetElement } from '../types/Worker';
   4
   5 import Utils from '../utils/Utils';
   6 import { Worker } from 'worker_threads';
   7 import WorkerAbstract from './WorkerAbstract';
   8 import { WorkerUtils } from './WorkerUtils';
   9
  10 export default class WorkerSet extends WorkerAbstract<WorkerData> {
  11   private readonly workerSet: Set<WorkerSetElement>;
  12   private readonly messageHandler: (message: unknown) => void | Promise<void>;
  13
  14   /**
  15    * Create a new `WorkerSet`.
  16    *
  17    * @param workerScript
  18    * @param workerOptions
  19    */
  20   constructor(workerScript: string, workerOptions?: WorkerOptions) {
  21     super(workerScript, workerOptions);
  22     this.workerSet = new Set<WorkerSetElement>();
  23     this.messageHandler =
  24       workerOptions?.messageHandler ??
  25       (() => {
  26         /* This is intentional */
  27       });
  28   }
  29
  30   get size(): number {
  31     return this.workerSet.size;
  32   }
  33
  34   get maxElementsPerWorker(): number | null {
  35     return this.workerOptions.elementsPerWorker;
  36   }
  37
  38   /**
  39    *
  40    * @param elementData
  41    * @returns
  42    * @public
  43    */
  44   public async addElement(elementData: WorkerData): Promise<void> {
  45     if (!this.workerSet) {
  46       throw new Error("Cannot add a WorkerSet element: workers' set does not exist");
  47     }
  48     if (
  49       this.getLastWorkerSetElement().numberOfWorkerElements >= this.workerOptions.elementsPerWorker
  50     ) {
  51       await this.startWorker();
  52     }
  53     this.getLastWorker().postMessage({
  54       id: WorkerMessageEvents.START_WORKER_ELEMENT,
  55       data: elementData,
  56     });
  57     this.getLastWorkerSetElement().numberOfWorkerElements++;
  58     // Start element sequentially to optimize memory at startup
  59     if (this.workerOptions.elementStartDelay > 0) {
  60       await Utils.sleep(this.workerOptions.elementStartDelay);
  61     }
  62   }
  63
  64   /**
  65    *
  66    * @returns
  67    * @public
  68    */
  69   public async start(): Promise<void> {
  70     await this.startWorker();
  71   }
  72
  73   /**
  74    *
  75    * @returns
  76    * @public
  77    */
  78   public async stop(): Promise<void> {
  79     for (const workerSetElement of this.workerSet) {
  80       await workerSetElement.worker.terminate();
  81     }
  82     this.workerSet.clear();
  83   }
  84
  85   /**
  86    *
  87    * @private
  88    */
  89   private async startWorker(): Promise<void> {
  90     const worker = new Worker(this.workerScript);
  91     worker.on('message', (msg) => {
  92       (async () => {
  93         await this.messageHandler(msg);
  94       })().catch(() => {
  95         /* This is intentional */
  96       });
  97     });
  98     worker.on('error', () => {
  99       /* This is intentional */
 100     });
 101     worker.on('exit', (code) => {
 102       WorkerUtils.defaultExitHandler(code);
 103       this.workerSet.delete(this.getWorkerSetElementByWorker(worker));
 104     });
 105     this.workerSet.add({ worker, numberOfWorkerElements: 0 });
 106     // Start worker sequentially to optimize memory at startup
 107     this.workerOptions.workerStartDelay > 0 &&
 108       (await Utils.sleep(this.workerOptions.workerStartDelay));
 109   }
 110
 111   private getLastWorkerSetElement(): WorkerSetElement {
 112     let workerSetElement: WorkerSetElement;
 113     for (workerSetElement of this.workerSet) {
 114       /* This is intentional */
 115     }
 116     return workerSetElement;
 117   }
 118
 119   private getLastWorker(): Worker {
 120     return this.getLastWorkerSetElement().worker;
 121   }
 122
 123   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement {
 124     let workerSetElt: WorkerSetElement;
 125     for (const workerSetElement of this.workerSet) {
 126       if (workerSetElement.worker.threadId === worker.threadId) {
 127         workerSetElt = workerSetElement;
 128         break;
 129       }
 130     }
 131     return workerSetElt;
 132   }
 133 }