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   StrategyPolicy,
   8   WorkerChoiceStrategyOptions
   9 } from './selection-strategies-types'
  10
  11 /**
  12  * Selects the least used worker.
  13  *
  14  * @typeParam Worker - Type of worker which manages the strategy.
  15  * @typeParam Data - Type of data sent to the worker. This can only be structured-cloneable data.
  16  * @typeParam Response - Type of execution response. This can only be structured-cloneable data.
  17  */
  18 export class LeastUsedWorkerChoiceStrategy<
  19     Worker extends IWorker,
  20     Data = unknown,
  21     Response = unknown
  22   >
  23   extends AbstractWorkerChoiceStrategy<Worker, Data, Response>
  24   implements IWorkerChoiceStrategy {
  25   /** @inheritDoc */
  26   public readonly strategyPolicy: StrategyPolicy = {
  27     dynamicWorkerUsage: false,
  28     dynamicWorkerReady: true
  29   }
  30
  31   /** @inheritDoc */
  32   public constructor (
  33     pool: IPool<Worker, Data, Response>,
  34     opts: WorkerChoiceStrategyOptions = DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS
  35   ) {
  36     super(pool, opts)
  37     this.setTaskStatisticsRequirements(this.opts)
  38   }
  39
  40   /** @inheritDoc */
  41   public reset (): boolean {
  42     return true
  43   }
  44
  45   /** @inheritDoc */
  46   public update (): boolean {
  47     return true
  48   }
  49
  50   /** @inheritDoc */
  51   public choose (): number | undefined {
  52     const chosenWorkerNodeKey = this.leastUsedNextWorkerNodeKey()
  53     this.assignChosenWorkerNodeKey(chosenWorkerNodeKey)
  54     return this.nextWorkerNodeKey
  55   }
  56
  57   /** @inheritDoc */
  58   public remove (): boolean {
  59     return true
  60   }
  61
  62   private leastUsedNextWorkerNodeKey (): number | undefined {
  63     let minNumberOfTasks = Infinity
  64     let chosenWorkerNodeKey: number | undefined
  65     for (const [workerNodeKey, workerNode] of this.pool.workerNodes.entries()) {
  66       const workerTaskStatistics = workerNode.usage.tasks
  67       const workerTasks =
  68         workerTaskStatistics.executed +
  69         workerTaskStatistics.executing +
  70         workerTaskStatistics.queued
  71       if (this.isWorkerNodeEligible(workerNodeKey) && workerTasks === 0) {
  72         chosenWorkerNodeKey = workerNodeKey
  73         break
  74       } else if (
  75         this.isWorkerNodeEligible(workerNodeKey) &&
  76         workerTasks < minNumberOfTasks
  77       ) {
  78         minNumberOfTasks = workerTasks
  79         chosenWorkerNodeKey = workerNodeKey
  80       }
  81     }
  82     return chosenWorkerNodeKey
  83   }
  84 }