src/worker/WorkerSet.ts

   1 // Partial Copyright Jerome Benoit. 2021. All Rights Reserved.
   2
   3 import { Worker } from 'worker_threads';
   4
   5 import { WorkerData, WorkerMessageEvents, WorkerOptions, WorkerSetElement } from '../types/Worker';
   6 import Utils from '../utils/Utils';
   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.workerSet.size === 0 ||
  50       this.getLastWorkerSetElement().numberOfWorkerElements >= this.workerOptions.elementsPerWorker
  51     ) {
  52       await this.startWorker();
  53     }
  54     this.getLastWorker().postMessage({
  55       id: WorkerMessageEvents.START_WORKER_ELEMENT,
  56       data: elementData,
  57     });
  58     this.getLastWorkerSetElement().numberOfWorkerElements++;
  59     // Start element sequentially to optimize memory at startup
  60     if (this.workerOptions.elementStartDelay > 0) {
  61       await Utils.sleep(this.workerOptions.elementStartDelay);
  62     }
  63   }
  64
  65   /**
  66    *
  67    * @returns
  68    * @public
  69    */
  70   public async start(): Promise<void> {
  71     await this.startWorker();
  72   }
  73
  74   /**
  75    *
  76    * @returns
  77    * @public
  78    */
  79   public async stop(): Promise<void> {
  80     for (const workerSetElement of this.workerSet) {
  81       await workerSetElement.worker.terminate();
  82     }
  83     this.workerSet.clear();
  84   }
  85
  86   /**
  87    *
  88    * @private
  89    */
  90   private async startWorker(): Promise<void> {
  91     const worker = new Worker(this.workerScript);
  92     worker.on('message', (msg) => {
  93       (async () => {
  94         await this.messageHandler(msg);
  95       })().catch(() => {
  96         /* This is intentional */
  97       });
  98     });
  99     worker.on('error', () => {
 100       /* This is intentional */
 101     });
 102     worker.on('exit', (code) => {
 103       WorkerUtils.defaultExitHandler(code);
 104       this.workerSet.delete(this.getWorkerSetElementByWorker(worker));
 105     });
 106     this.workerSet.add({ worker, numberOfWorkerElements: 0 });
 107     // Start worker sequentially to optimize memory at startup
 108     this.workerOptions.workerStartDelay > 0 &&
 109       (await Utils.sleep(this.workerOptions.workerStartDelay));
 110   }
 111
 112   private getLastWorkerSetElement(): WorkerSetElement {
 113     let workerSetElement: WorkerSetElement;
 114     for (workerSetElement of this.workerSet) {
 115       /* This is intentional */
 116     }
 117     return workerSetElement;
 118   }
 119
 120   private getLastWorker(): Worker {
 121     return this.getLastWorkerSetElement().worker;
 122   }
 123
 124   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement {
 125     let workerSetElt: WorkerSetElement;
 126     for (const workerSetElement of this.workerSet) {
 127       if (workerSetElement.worker.threadId === worker.threadId) {
 128         workerSetElt = workerSetElement;
 129         break;
 130       }
 131     }
 132     return workerSetElt;
 133   }
 134 }