src/pools/selection-strategies/fair-share-worker-choice-strategy.ts

   1 import {
   2   DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS,
   3   DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS
   4 } from '../../utils'
   5 import type { IPool } from '../pool'
   6 import type { IWorker } from '../worker'
   7 import { AbstractWorkerChoiceStrategy } from './abstract-worker-choice-strategy'
   8 import {
   9   type IWorkerChoiceStrategy,
  10   Measurements,
  11   type TaskStatisticsRequirements,
  12   type WorkerChoiceStrategyOptions
  13 } from './selection-strategies-types'
  14
  15 /**
  16  * Selects the next worker with a fair share scheduling algorithm.
  17  * Loosely modeled after the fair queueing algorithm: https://en.wikipedia.org/wiki/Fair_queuing.
  18  *
  19  * @typeParam Worker - Type of worker which manages the strategy.
  20  * @typeParam Data - Type of data sent to the worker. This can only be structured-cloneable data.
  21  * @typeParam Response - Type of execution response. This can only be structured-cloneable data.
  22  */
  23 export class FairShareWorkerChoiceStrategy<
  24     Worker extends IWorker,
  25     Data = unknown,
  26     Response = unknown
  27   >
  28   extends AbstractWorkerChoiceStrategy<Worker, Data, Response>
  29   implements IWorkerChoiceStrategy {
  30   /** @inheritDoc */
  31   public readonly taskStatisticsRequirements: TaskStatisticsRequirements = {
  32     runTime: {
  33       aggregate: true,
  34       average: true,
  35       median: false
  36     },
  37     waitTime: DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS,
  38     elu: {
  39       aggregate: true,
  40       average: true,
  41       median: false
  42     }
  43   }
  44
  45   /**
  46    * Workers' virtual task end execution timestamp.
  47    */
  48   private workersVirtualTaskEndTimestamp: number[] = []
  49
  50   /** @inheritDoc */
  51   public constructor (
  52     pool: IPool<Worker, Data, Response>,
  53     opts: WorkerChoiceStrategyOptions = DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS
  54   ) {
  55     super(pool, opts)
  56     this.setTaskStatisticsRequirements(this.opts)
  57   }
  58
  59   /** @inheritDoc */
  60   public reset (): boolean {
  61     this.workersVirtualTaskEndTimestamp = []
  62     return true
  63   }
  64
  65   /** @inheritDoc */
  66   public update (workerNodeKey: number): boolean {
  67     this.computeWorkerVirtualTaskEndTimestamp(workerNodeKey)
  68     return true
  69   }
  70
  71   /** @inheritDoc */
  72   public choose (): number {
  73     let minWorkerVirtualTaskEndTimestamp = Infinity
  74     for (const [workerNodeKey] of this.pool.workerNodes.entries()) {
  75       if (this.workersVirtualTaskEndTimestamp[workerNodeKey] == null) {
  76         this.computeWorkerVirtualTaskEndTimestamp(workerNodeKey)
  77       }
  78       const workerVirtualTaskEndTimestamp =
  79         this.workersVirtualTaskEndTimestamp[workerNodeKey]
  80       if (
  81         this.workerNodeReady(workerNodeKey) &&
  82         workerVirtualTaskEndTimestamp < minWorkerVirtualTaskEndTimestamp
  83       ) {
  84         minWorkerVirtualTaskEndTimestamp = workerVirtualTaskEndTimestamp
  85         this.nextWorkerNodeId = workerNodeKey
  86       }
  87     }
  88     return this.nextWorkerNodeId
  89   }
  90
  91   /** @inheritDoc */
  92   public remove (workerNodeKey: number): boolean {
  93     this.workersVirtualTaskEndTimestamp.splice(workerNodeKey, 1)
  94     return true
  95   }
  96
  97   /**
  98    * Computes the worker node key virtual task end timestamp.
  99    *
 100    * @param workerNodeKey - The worker node key.
 101    */
 102   private computeWorkerVirtualTaskEndTimestamp (workerNodeKey: number): void {
 103     this.workersVirtualTaskEndTimestamp[workerNodeKey] =
 104       this.getWorkerVirtualTaskEndTimestamp(
 105         workerNodeKey,
 106         this.getWorkerVirtualTaskStartTimestamp(workerNodeKey)
 107       )
 108   }
 109
 110   private getWorkerVirtualTaskEndTimestamp (
 111     workerNodeKey: number,
 112     workerVirtualTaskStartTimestamp: number
 113   ): number {
 114     const workerTaskRunTime =
 115       this.opts.measurement === Measurements.elu
 116         ? this.getWorkerTaskElu(workerNodeKey)
 117         : this.getWorkerTaskRunTime(workerNodeKey)
 118     return workerVirtualTaskStartTimestamp + workerTaskRunTime
 119   }
 120
 121   private getWorkerVirtualTaskStartTimestamp (workerNodeKey: number): number {
 122     return Math.max(
 123       performance.now(),
 124       this.workersVirtualTaskEndTimestamp[workerNodeKey] ?? -Infinity
 125     )
 126   }
 127 }