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({
  48       id: WorkerMessageEvents.START_WORKER_ELEMENT,
  49       data: elementData
  50     });
  51     this.getLastWorkerSetElement().numberOfWorkerElements++;
  52     // Start element sequentially to optimize memory at startup
  53     if (this.workerOptions.elementStartDelay > 0) {
  54       await Utils.sleep(this.workerOptions.elementStartDelay);
  55     }
  56   }
  57
  58   /**
  59    *
  60    * @returns
  61    * @public
  62    */
  63   public async start(): Promise<void> {
  64     await this.startWorker();
  65   }
  66
  67   /**
  68    *
  69    * @returns
  70    * @public
  71    */
  72   public async stop(): Promise<void> {
  73     for (const workerSetElement of this.workerSet) {
  74       await workerSetElement.worker.terminate();
  75     }
  76     this.workerSet.clear();
  77   }
  78
  79   /**
  80    *
  81    * @private
  82    */
  83   private async startWorker(): Promise<void> {
  84     const worker = new Worker(this.workerScript);
  85     worker.on('message', (msg) => {
  86       (async () => {
  87         await this.messageHandler(msg);
  88       })().catch(() => { /* This is intentional */ });
  89     });
  90     worker.on('error', () => { /* This is intentional */ });
  91     worker.on('exit', (code) => {
  92       WorkerUtils.defaultExitHandler(code);
  93       this.workerSet.delete(this.getWorkerSetElementByWorker(worker));
  94     });
  95     this.workerSet.add({ worker, numberOfWorkerElements: 0 });
  96     // Start worker sequentially to optimize memory at startup
  97     this.workerOptions.workerStartDelay > 0 && await Utils.sleep(this.workerOptions.workerStartDelay);
  98   }
  99
 100   private getLastWorkerSetElement(): WorkerSetElement {
 101     let workerSetElement: WorkerSetElement;
 102     for (workerSetElement of this.workerSet) { /* This is intentional */ }
 103     return workerSetElement;
 104   }
 105
 106   private getLastWorker(): Worker {
 107     return this.getLastWorkerSetElement().worker;
 108   }
 109
 110   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement {
 111     let workerSetElt: WorkerSetElement;
 112     for (const workerSetElement of this.workerSet) {
 113       if (workerSetElement.worker.threadId === worker.threadId) {
 114         workerSetElt = workerSetElement;
 115         break;
 116       }
 117     }
 118     return workerSetElt;
 119   }
 120 }