src/pools/selection-strategies/least-used-worker-choice-strategy.ts

   1 import { DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS } from '../../utils'
   2 import type { IPool } from '../pool'
   3 import type { IWorker } from '../worker'
   4 import { AbstractWorkerChoiceStrategy } from './abstract-worker-choice-strategy'
   5 import type {
   6   IWorkerChoiceStrategy,
   7   WorkerChoiceStrategyOptions
   8 } from './selection-strategies-types'
   9
  10 /**
  11  * Selects the least used worker.
  12  *
  13  * @typeParam Worker - Type of worker which manages the strategy.
  14  * @typeParam Data - Type of data sent to the worker. This can only be structured-cloneable data.
  15  * @typeParam Response - Type of execution response. This can only be structured-cloneable data.
  16  */
  17 export class LeastUsedWorkerChoiceStrategy<
  18     Worker extends IWorker,
  19     Data = unknown,
  20     Response = unknown
  21   >
  22   extends AbstractWorkerChoiceStrategy<Worker, Data, Response>
  23   implements IWorkerChoiceStrategy {
  24   /** @inheritDoc */
  25   public constructor (
  26     pool: IPool<Worker, Data, Response>,
  27     opts: WorkerChoiceStrategyOptions = DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS
  28   ) {
  29     super(pool, opts)
  30     this.setTaskStatisticsRequirements(this.opts)
  31   }
  32
  33   /** @inheritDoc */
  34   public reset (): boolean {
  35     return true
  36   }
  37
  38   /** @inheritDoc */
  39   public update (): boolean {
  40     return true
  41   }
  42
  43   /** @inheritDoc */
  44   public choose (): number | undefined {
  45     this.setPreviousWorkerNodeKey(this.nextWorkerNodeKey)
  46     this.nextWorkerNodeKey = this.leastUsedNextWorkerNodeKey()
  47     return this.nextWorkerNodeKey
  48   }
  49
  50   /** @inheritDoc */
  51   public remove (): boolean {
  52     return true
  53   }
  54
  55   private leastUsedNextWorkerNodeKey (): number | undefined {
  56     let chosenWorkerNodeKey: number | undefined
  57     let minNumberOfTasks = Infinity
  58     for (const [workerNodeKey, workerNode] of this.pool.workerNodes.entries()) {
  59       const workerTaskStatistics = workerNode.usage.tasks
  60       const workerTasks =
  61         workerTaskStatistics.executed +
  62         workerTaskStatistics.executing +
  63         workerTaskStatistics.queued
  64       if (workerTasks === 0) {
  65         chosenWorkerNodeKey = workerNodeKey
  66         break
  67       } else if (workerTasks < minNumberOfTasks) {
  68         minNumberOfTasks = workerTasks
  69         chosenWorkerNodeKey = workerNodeKey
  70       }
  71     }
  72     return chosenWorkerNodeKey
  73   }
  74 }