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, data: elementData });
  48     this.getLastWorkerSetElement().numberOfWorkerElements++;
  49     this.workerOptions.elementStartDelay > 0 && await Utils.sleep(this.workerOptions.elementStartDelay);
  50   }
  51
  52   /**
  53    *
  54    * @returns
  55    * @public
  56    */
  57   public async start(): Promise<void> {
  58     await this.startWorker();
  59   }
  60
  61   /**
  62    *
  63    * @returns
  64    * @public
  65    */
  66   public async stop(): Promise<void> {
  67     for (const workerSetElement of this.workerSet) {
  68       await workerSetElement.worker.terminate();
  69     }
  70     this.workerSet.clear();
  71   }
  72
  73   /**
  74    *
  75    * @private
  76    */
  77   private async startWorker(): Promise<void> {
  78     const worker = new Worker(this.workerScript);
  79     worker.on('message', (msg) => {
  80       (async () => {
  81         await this.messageHandler(msg);
  82       })().catch(() => { /* This is intentional */ });
  83     });
  84     worker.on('error', () => { /* This is intentional */ });
  85     worker.on('exit', (code) => {
  86       WorkerUtils.defaultExitHandler(code);
  87       this.workerSet.delete(this.getWorkerSetElementByWorker(worker));
  88     });
  89     this.workerSet.add({ worker, numberOfWorkerElements: 0 });
  90     // Start worker sequentially to optimize memory at startup
  91     this.workerOptions.workerStartDelay > 0 && await Utils.sleep(this.workerOptions.workerStartDelay);
  92   }
  93
  94   private getLastWorkerSetElement(): WorkerSetElement {
  95     let workerSetElement: WorkerSetElement;
  96     for (workerSetElement of this.workerSet) { /* This is intentional */ }
  97     return workerSetElement;
  98   }
  99
 100   private getLastWorker(): Worker {
 101     return this.getLastWorkerSetElement().worker;
 102   }
 103
 104   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement {
 105     let workerSetElt: WorkerSetElement;
 106     for (const workerSetElement of this.workerSet) {
 107       if (workerSetElement.worker.threadId === worker.threadId) {
 108         workerSetElt = workerSetElement;
 109         break;
 110       }
 111     }
 112     return workerSetElt;
 113   }
 114 }