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.nextWorkerNodeKey = this.leastUsedNextWorkerNodeKey()
  46     return this.nextWorkerNodeKey
  47   }
  48
  49   /** @inheritDoc */
  50   public remove (): boolean {
  51     return true
  52   }
  53
  54   private leastUsedNextWorkerNodeKey (): number | undefined {
  55     let minNumberOfTasks = Infinity
  56     let chosenWorkerNodeKey: number | undefined
  57     for (const [workerNodeKey, workerNode] of this.pool.workerNodes.entries()) {
  58       const workerTaskStatistics = workerNode.usage.tasks
  59       const workerTasks =
  60         workerTaskStatistics.executed +
  61         workerTaskStatistics.executing +
  62         workerTaskStatistics.queued
  63       if (this.isWorkerNodeEligible(workerNodeKey) && workerTasks === 0) {
  64         chosenWorkerNodeKey = workerNodeKey
  65         break
  66       } else if (
  67         this.isWorkerNodeEligible(workerNodeKey) &&
  68         workerTasks < minNumberOfTasks
  69       ) {
  70         minNumberOfTasks = workerTasks
  71         chosenWorkerNodeKey = workerNodeKey
  72       }
  73     }
  74     return chosenWorkerNodeKey
  75   }
  76 }