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 { defaultErrorHandler, defaultExitHandler, sleep } 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   /** @inheritDoc */
  39   public async addElement(elementData: WorkerData): Promise<void> {
  40     if (!this.workerSet) {
  41       throw new Error("Cannot add a WorkerSet element: workers' set does not exist");
  42     }
  43     let lastWorkerSetElement = this.getLastWorkerSetElement();
  44     if (
  45       this.workerSet.size === 0 ||
  46       lastWorkerSetElement.numberOfWorkerElements >= this.workerOptions.elementsPerWorker
  47     ) {
  48       this.startWorker();
  49       // Start worker sequentially to optimize memory at startup
  50       this.workerOptions.workerStartDelay > 0 && (await sleep(this.workerOptions.workerStartDelay));
  51       lastWorkerSetElement = this.getLastWorkerSetElement();
  52     }
  53     lastWorkerSetElement.worker.postMessage({
  54       id: WorkerMessageEvents.startWorkerElement,
  55       data: elementData,
  56     });
  57     ++lastWorkerSetElement.numberOfWorkerElements;
  58     // Start element sequentially to optimize memory at startup
  59     if (this.workerOptions.elementStartDelay > 0) {
  60       await sleep(this.workerOptions.elementStartDelay);
  61     }
  62   }
  63
  64   /** @inheritDoc */
  65   public async start(): Promise<void> {
  66     this.startWorker();
  67     // Start worker sequentially to optimize memory at startup
  68     this.workerOptions.workerStartDelay > 0 && (await sleep(this.workerOptions.workerStartDelay));
  69   }
  70
  71   /** @inheritDoc */
  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    * Start a new `Worker`.
  81    */
  82   private startWorker(): void {
  83     const worker = new Worker(this.workerScript);
  84     worker.on(
  85       'message',
  86       (this.workerOptions?.messageHandler ?? WorkerConstants.EMPTY_FUNCTION).bind(
  87         this
  88       ) as MessageHandler<Worker>
  89     );
  90     worker.on('error', defaultErrorHandler.bind(this) as (err: Error) => void);
  91     worker.on('error', () => this.startWorker());
  92     worker.on('exit', defaultExitHandler.bind(this) as (exitCode: number) => void);
  93     worker.on('exit', () => this.workerSet.delete(this.getWorkerSetElementByWorker(worker)));
  94     this.workerSet.add({ worker, numberOfWorkerElements: 0 });
  95   }
  96
  97   private getLastWorkerSetElement(): WorkerSetElement {
  98     let workerSetElement: WorkerSetElement;
  99     for (workerSetElement of this.workerSet) {
 100       /* This is intentional */
 101     }
 102     return workerSetElement;
 103   }
 104
 105   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement {
 106     let workerSetElt: WorkerSetElement;
 107     for (const workerSetElement of this.workerSet) {
 108       if (workerSetElement.worker.threadId === worker.threadId) {
 109         workerSetElt = workerSetElement;
 110         break;
 111       }
 112     }
 113     return workerSetElt;
 114   }
 115 }