src/worker/WorkerSet.ts

   1 // Partial Copyright Jerome Benoit. 2021. All Rights Reserved.
   2
   3 import { 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<T> extends WorkerAbstract {
  11   public readonly maxElementsPerWorker: number;
  12   private readonly messageHandler: (message: unknown) => void | Promise<void>;
  13   private workerSet: Set<WorkerSetElement>;
  14
  15   /**
  16    * Create a new `WorkerSet`.
  17    *
  18    * @param workerScript
  19    * @param maxElementsPerWorker
  20    * @param workerStartDelay
  21    * @param opts
  22    */
  23   constructor(workerScript: string, maxElementsPerWorker = 1, workerStartDelay?: number, opts?: WorkerOptions) {
  24     super(workerScript, workerStartDelay);
  25     this.maxElementsPerWorker = maxElementsPerWorker;
  26     this.messageHandler = opts?.messageHandler ?? (() => { });
  27     this.workerSet = new Set<WorkerSetElement>();
  28   }
  29
  30   get size(): number {
  31     return this.workerSet.size;
  32   }
  33
  34   /**
  35    *
  36    * @param elementData
  37    * @returns
  38    * @public
  39    */
  40   public async addElement(elementData: T): 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.maxElementsPerWorker) {
  45       this.startWorker();
  46       // Start worker sequentially to optimize memory at startup
  47       await Utils.sleep(this.workerStartDelay);
  48     }
  49     this.getLastWorker().postMessage({ id: WorkerMessageEvents.START_WORKER_ELEMENT, data: elementData });
  50     this.getLastWorkerSetElement().numberOfWorkerElements++;
  51   }
  52
  53   /**
  54    *
  55    * @returns
  56    * @public
  57    */
  58   public async start(): Promise<void> {
  59     this.startWorker();
  60     // Start worker sequentially to optimize memory at startup
  61     await Utils.sleep(this.workerStartDelay);
  62   }
  63
  64   /**
  65    *
  66    * @returns
  67    * @public
  68    */
  69   public async stop(): Promise<void> {
  70     for (const workerSetElement of this.workerSet) {
  71       await workerSetElement.worker.terminate();
  72     }
  73     this.workerSet.clear();
  74   }
  75
  76   /**
  77    *
  78    * @private
  79    */
  80   private startWorker(): void {
  81     const worker = new Worker(this.workerScript);
  82     worker.on('message', (msg) => {
  83       (async () => {
  84         await this.messageHandler(msg);
  85       })().catch(() => {});
  86     });
  87     worker.on('error', () => { /* This is intentional */ });
  88     worker.on('exit', (code) => {
  89       WorkerUtils.defaultExitHandler(code);
  90       this.workerSet.delete(this.getWorkerSetElementByWorker(worker));
  91     });
  92     this.workerSet.add({ worker, numberOfWorkerElements: 0 });
  93   }
  94
  95   private getLastWorkerSetElement(): WorkerSetElement {
  96     let workerSetElement: WorkerSetElement;
  97     // eslint-disable-next-line no-empty
  98     for (workerSetElement of this.workerSet) { /* This is intentional */ }
  99     return workerSetElement;
 100   }
 101
 102   private getLastWorker(): Worker {
 103     return this.getLastWorkerSetElement().worker;
 104   }
 105
 106   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement {
 107     let workerSetElt: WorkerSetElement;
 108     for (const workerSetElement of this.workerSet) {
 109       if (workerSetElement.worker.threadId === worker.threadId) {
 110         workerSetElt = workerSetElement;
 111         break;
 112       }
 113     }
 114     return workerSetElt;
 115   }
 116 }