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 = workerOptions?.messageHandler ?? (() => { /* This is intentional */ });
  24   }
  25
  26   get size(): number {
  27     return this.workerSet.size;
  28   }
  29
  30   get maxElementsPerWorker(): number | null {
  31     return this.workerOptions.elementsPerWorker;
  32   }
  33
  34   /**
  35    *
  36    * @param elementData
  37    * @returns
  38    * @public
  39    */
  40   public async addElement(elementData: WorkerData): Promise<void> {
  41     if (!this.workerSet) {
  42       throw new Error('Cannot add a WorkerSet element: workers\' set does not exist');
  43     }
  44     if (this.getLastWorkerSetElement().numberOfWorkerElements >= this.workerOptions.elementsPerWorker) {
  45       await this.startWorker();
  46     }
  47     this.getLastWorker().postMessage({ id: WorkerMessageEvents.START_WORKER_ELEMENT, workerOptions: this.workerOptions, data: elementData });
  48     this.getLastWorkerSetElement().numberOfWorkerElements++;
  49   }
  50
  51   /**
  52    *
  53    * @returns
  54    * @public
  55    */
  56   public async start(): Promise<void> {
  57     await this.startWorker();
  58   }
  59
  60   /**
  61    *
  62    * @returns
  63    * @public
  64    */
  65   public async stop(): Promise<void> {
  66     for (const workerSetElement of this.workerSet) {
  67       await workerSetElement.worker.terminate();
  68     }
  69     this.workerSet.clear();
  70   }
  71
  72   /**
  73    *
  74    * @private
  75    */
  76   private async startWorker(): Promise<void> {
  77     const worker = new Worker(this.workerScript);
  78     worker.on('message', (msg) => {
  79       (async () => {
  80         await this.messageHandler(msg);
  81       })().catch(() => { /* This is intentional */ });
  82     });
  83     worker.on('error', () => { /* This is intentional */ });
  84     worker.on('exit', (code) => {
  85       WorkerUtils.defaultExitHandler(code);
  86       this.workerSet.delete(this.getWorkerSetElementByWorker(worker));
  87     });
  88     this.workerSet.add({ worker, numberOfWorkerElements: 0 });
  89     // Start worker sequentially to optimize memory at startup
  90     this.workerOptions.workerStartDelay > 0 && await Utils.sleep(this.workerOptions.workerStartDelay);
  91   }
  92
  93   private getLastWorkerSetElement(): WorkerSetElement {
  94     let workerSetElement: WorkerSetElement;
  95     for (workerSetElement of this.workerSet) { /* This is intentional */ }
  96     return workerSetElement;
  97   }
  98
  99   private getLastWorker(): Worker {
 100     return this.getLastWorkerSetElement().worker;
 101   }
 102
 103   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement {
 104     let workerSetElt: WorkerSetElement;
 105     for (const workerSetElement of this.workerSet) {
 106       if (workerSetElement.worker.threadId === worker.threadId) {
 107         workerSetElt = workerSetElement;
 108         break;
 109       }
 110     }
 111     return workerSetElt;
 112   }
 113 }