src/worker/WorkerSet.ts

   1 // Partial Copyright Jerome Benoit. 2021-2023. All Rights Reserved.
   2
   3 import { Worker } from 'node:worker_threads';
   4
   5 import { WorkerAbstract } from './WorkerAbstract';
   6 import { WorkerConstants } from './WorkerConstants';
   7 import {
   8   type MessageHandler,
   9   type WorkerData,
  10   WorkerMessageEvents,
  11   type WorkerOptions,
  12   type WorkerSetElement,
  13 } from './WorkerTypes';
  14 import { WorkerUtils } from './WorkerUtils';
  15
  16 export class WorkerSet extends WorkerAbstract<WorkerData> {
  17   private readonly workerSet: Set<WorkerSetElement>;
  18
  19   /**
  20    * Create a new `WorkerSet`.
  21    *
  22    * @param workerScript -
  23    * @param workerOptions -
  24    */
  25   constructor(workerScript: string, workerOptions?: WorkerOptions) {
  26     super(workerScript, workerOptions);
  27     this.workerSet = new Set<WorkerSetElement>();
  28   }
  29
  30   get size(): number {
  31     return this.workerSet.size;
  32   }
  33
  34   get maxElementsPerWorker(): number | undefined {
  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.startWorkerElement,
  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 WorkerUtils.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    * Start a new `Worker`.
  88    */
  89   private async startWorker(): Promise<void> {
  90     const worker = new Worker(this.workerScript);
  91     worker.on(
  92       'message',
  93       (this.workerOptions?.messageHandler ?? WorkerConstants.EMPTY_FUNCTION).bind(
  94         this
  95       ) as MessageHandler<Worker>
  96     );
  97     worker.on('error', WorkerUtils.defaultErrorHandler.bind(this) as (err: Error) => void);
  98     worker.on('exit', (code) => {
  99       WorkerUtils.defaultExitHandler(code);
 100       this.workerSet.delete(this.getWorkerSetElementByWorker(worker));
 101     });
 102     this.workerSet.add({ worker, numberOfWorkerElements: 0 });
 103     // Start worker sequentially to optimize memory at startup
 104     this.workerOptions.workerStartDelay > 0 &&
 105       (await WorkerUtils.sleep(this.workerOptions.workerStartDelay));
 106   }
 107
 108   private getLastWorkerSetElement(): WorkerSetElement {
 109     let workerSetElement: WorkerSetElement;
 110     for (workerSetElement of this.workerSet) {
 111       /* This is intentional */
 112     }
 113     return workerSetElement;
 114   }
 115
 116   private getLastWorker(): Worker {
 117     return this.getLastWorkerSetElement().worker;
 118   }
 119
 120   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement {
 121     let workerSetElt: WorkerSetElement;
 122     for (const workerSetElement of this.workerSet) {
 123       if (workerSetElement.worker.threadId === worker.threadId) {
 124         workerSetElt = workerSetElement;
 125         break;
 126       }
 127     }
 128     return workerSetElt;
 129   }
 130 }