src/worker/WorkerSet.ts

   1 // Partial Copyright Jerome Benoit. 2021-2023. All Rights Reserved.
   2
   3 import EventEmitterAsyncResource from 'node:events';
   4 import { Worker } from 'node:worker_threads';
   5
   6 import { WorkerAbstract } from './WorkerAbstract';
   7 import { WorkerConstants } from './WorkerConstants';
   8 import {
   9   type MessageHandler,
  10   type SetInfo,
  11   type WorkerData,
  12   WorkerMessageEvents,
  13   type WorkerOptions,
  14   type WorkerSetElement,
  15 } from './WorkerTypes';
  16 import { defaultErrorHandler, defaultExitHandler, sleep } from './WorkerUtils';
  17
  18 export class WorkerSet extends WorkerAbstract<WorkerData> {
  19   public readonly emitter: EventEmitterAsyncResource;
  20   private readonly workerSet: Set<WorkerSetElement>;
  21
  22   /**
  23    * Create a new `WorkerSet`.
  24    *
  25    * @param workerScript -
  26    * @param workerOptions -
  27    */
  28   constructor(workerScript: string, workerOptions?: WorkerOptions) {
  29     super(workerScript, workerOptions);
  30     this.workerSet = new Set<WorkerSetElement>();
  31     this.emitter = new EventEmitterAsyncResource();
  32   }
  33
  34   get info(): SetInfo {
  35     return {
  36       size: this.size,
  37       runningElements: [...this.workerSet].reduce(
  38         (accumulator, workerSetElement) => accumulator + workerSetElement.numberOfWorkerElements,
  39         0
  40       ),
  41       elementsPerWorker: this.maxElementsPerWorker,
  42     };
  43   }
  44
  45   get size(): number {
  46     return this.workerSet.size;
  47   }
  48
  49   get maxElementsPerWorker(): number | undefined {
  50     return this.workerOptions.elementsPerWorker;
  51   }
  52
  53   /** @inheritDoc */
  54   public async start(): Promise<void> {
  55     this.addWorkerSetElement();
  56     // Add worker set element sequentially to optimize memory at startup
  57     this.workerOptions.workerStartDelay > 0 && (await sleep(this.workerOptions.workerStartDelay));
  58   }
  59
  60   /** @inheritDoc */
  61   public async stop(): Promise<void> {
  62     for (const workerSetElement of this.workerSet) {
  63       await workerSetElement.worker.terminate();
  64     }
  65     this.workerSet.clear();
  66   }
  67
  68   /** @inheritDoc */
  69   public async addElement(elementData: WorkerData): Promise<void> {
  70     if (!this.workerSet) {
  71       throw new Error("Cannot add a WorkerSet element: workers' set does not exist");
  72     }
  73     const workerSetElement = await this.getWorkerSetElement();
  74     workerSetElement.worker.postMessage({
  75       id: WorkerMessageEvents.startWorkerElement,
  76       data: elementData,
  77     });
  78     ++workerSetElement.numberOfWorkerElements;
  79     // Add element sequentially to optimize memory at startup
  80     if (this.workerOptions.elementStartDelay > 0) {
  81       await sleep(this.workerOptions.elementStartDelay);
  82     }
  83   }
  84
  85   /**
  86    * Add a new `WorkerSetElement`.
  87    */
  88   private addWorkerSetElement(): WorkerSetElement {
  89     const worker = new Worker(this.workerScript);
  90     worker.on(
  91       'message',
  92       (this.workerOptions?.messageHandler ?? WorkerConstants.EMPTY_FUNCTION).bind(
  93         this
  94       ) as MessageHandler<Worker>
  95     );
  96     worker.on('error', defaultErrorHandler.bind(this) as (err: Error) => void);
  97     worker.on('error', (error) => {
  98       this.emitter.emit('error', error);
  99       this.addWorkerSetElement();
 100     });
 101     worker.on('exit', defaultExitHandler.bind(this) as (exitCode: number) => void);
 102     worker.on('exit', () => this.workerSet.delete(this.getWorkerSetElementByWorker(worker)));
 103     const workerSetElement: WorkerSetElement = { worker, numberOfWorkerElements: 0 };
 104     this.workerSet.add(workerSetElement);
 105     return workerSetElement;
 106   }
 107
 108   private async getWorkerSetElement(): Promise<WorkerSetElement> {
 109     let chosenWorkerSetElement: WorkerSetElement;
 110     for (const workerSetElement of this.workerSet) {
 111       if (workerSetElement.numberOfWorkerElements < this.workerOptions.elementsPerWorker) {
 112         chosenWorkerSetElement = workerSetElement;
 113         break;
 114       }
 115     }
 116     if (!chosenWorkerSetElement) {
 117       chosenWorkerSetElement = this.addWorkerSetElement();
 118       // Add worker set element sequentially to optimize memory at startup
 119       this.workerOptions.workerStartDelay > 0 && (await sleep(this.workerOptions.workerStartDelay));
 120     }
 121     return chosenWorkerSetElement;
 122   }
 123
 124   private getWorkerSetElementByWorker(worker: Worker): WorkerSetElement | undefined {
 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 }