src/pools/cluster/dynamic.ts

   1 import type { Worker } from 'cluster'
   2 import type { JSONValue, MessageValue } from '../../utility-types'
   3 import type { ClusterPoolOptions } from './fixed'
   4 import { FixedClusterPool } from './fixed'
   5
   6 /**
   7  * A cluster pool with a dynamic number of workers, but a guaranteed minimum number of workers.
   8  *
   9  * This cluster pool creates new workers when the others are busy, up to the maximum number of workers.
  10  * When the maximum number of workers is reached, an event is emitted. If you want to listen to this event, use the pool's `emitter`.
  11  *
  12  * @template Data Type of data sent to the worker.
  13  * @template Response Type of response of execution.
  14  *
  15  * @author [Christopher Quadflieg](https://github.com/Shinigami92)
  16  * @since 2.0.0
  17  */
  18 export class DynamicClusterPool<
  19   Data extends JSONValue = JSONValue,
  20   Response extends JSONValue = JSONValue
  21 > extends FixedClusterPool<Data, Response> {
  22   /**
  23    * Constructs a new poolifier dynamic cluster pool.
  24    *
  25    * @param min Minimum number of workers which are always active.
  26    * @param max Maximum number of workers that can be created by this pool.
  27    * @param filename Path to an implementation of a `ClusterWorker` file, which can be relative or absolute.
  28    * @param opts Options for this fixed cluster pool. Default: `{ maxTasks: 1000 }`
  29    */
  30   public constructor (
  31     min: number,
  32     public readonly max: number,
  33     filename: string,
  34     opts: ClusterPoolOptions = { maxTasks: 1000 }
  35   ) {
  36     super(min, filename, opts)
  37   }
  38
  39   /**
  40    * Choose a worker for the next task.
  41    *
  42    * It will first check for and return an idle worker.
  43    * If all workers are busy, then it will try to create a new one up to the `max` worker count.
  44    * If the max worker count is reached, the emitter will emit a `FullPool` event and it will fall back to using a round robin algorithm to distribute the load.
  45    */
  46   protected chooseWorker (): Worker {
  47     let worker: Worker | undefined
  48     for (const entry of this.tasks) {
  49       if (entry[1] === 0) {
  50         worker = entry[0]
  51         break
  52       }
  53     }
  54
  55     if (worker) {
  56       // A worker is free, use it
  57       return worker
  58     } else {
  59       if (this.workers.length === this.max) {
  60         this.emitter.emit('FullPool')
  61         return super.chooseWorker()
  62       }
  63       // All workers are busy, create a new worker
  64       const worker = this.internalNewWorker()
  65       worker.on('message', (message: MessageValue<Data>) => {
  66         if (message.kill) {
  67           this.sendToWorker(worker, { kill: 1 })
  68           void this.destroyWorker(worker)
  69           this.removeWorker(worker)
  70         }
  71       })
  72       return worker
  73     }
  74   }
  75 }