src/pools/thread/dynamic.ts

   1 import type { JSONValue, MessageValue } from '../../utility-types'
   2 import type { PoolOptions } from '../abstract-pool'
   3 import type { ThreadWorkerWithMessageChannel } from './fixed'
   4 import { FixedThreadPool } from './fixed'
   5
   6 /**
   7  * A thread pool with a min/max number of threads, is possible to execute tasks in sync or async mode as you prefer.
   8  *
   9  * This thread pool will create new workers when the other ones are busy, until the max number of threads,
  10  * when the max number of threads is reached, an event will be emitted, if you want to listen this event use the emitter method.
  11  *
  12  * @author [Alessandro Pio Ardizio](https://github.com/pioardi)
  13  * @since 0.0.1
  14  */
  15 export class DynamicThreadPool<
  16   Data extends JSONValue = JSONValue,
  17   Response extends JSONValue = JSONValue
  18 > extends FixedThreadPool<Data, Response> {
  19   /**
  20    * @param min Min number of threads that will be always active
  21    * @param max Max number of threads that will be active
  22    * @param filename A file path with implementation of `ThreadWorker` class, relative path is fine.
  23    * @param opts An object with possible options for example `errorHandler`, `onlineHandler`. Default: `{ maxTasks: 1000 }`
  24    */
  25   public constructor (
  26     min: number,
  27     public readonly max: number,
  28     filename: string,
  29     opts: PoolOptions<ThreadWorkerWithMessageChannel> = { maxTasks: 1000 }
  30   ) {
  31     super(min, filename, opts)
  32   }
  33
  34   protected chooseWorker (): ThreadWorkerWithMessageChannel {
  35     let worker: ThreadWorkerWithMessageChannel | undefined
  36     for (const entry of this.tasks) {
  37       if (entry[1] === 0) {
  38         worker = entry[0]
  39         break
  40       }
  41     }
  42
  43     if (worker) {
  44       // a worker is free, use it
  45       return worker
  46     } else {
  47       if (this.workers.length === this.max) {
  48         this.emitter.emit('FullPool')
  49         return super.chooseWorker()
  50       }
  51       // all workers are busy create a new worker
  52       const worker = this.internalNewWorker()
  53       worker.port2?.on('message', (message: MessageValue<Data>) => {
  54         if (message.kill) {
  55           this.sendToWorker(worker, { kill: 1 })
  56           void this.destroyWorker(worker)
  57           // clean workers from data structures
  58           const workerIndex = this.workers.indexOf(worker)
  59           this.workers.splice(workerIndex, 1)
  60           this.tasks.delete(worker)
  61         }
  62       })
  63       return worker
  64     }
  65   }
  66 }