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

   1 import { DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS } from '../../utils.js'
   2 import type { IPool } from '../pool.js'
   3 import type { IWorker, StrategyData } from '../worker.js'
   4 import { AbstractWorkerChoiceStrategy } from './abstract-worker-choice-strategy.js'
   5 import {
   6   type IWorkerChoiceStrategy,
   7   type InternalWorkerChoiceStrategyOptions,
   8   Measurements,
   9   type TaskStatisticsRequirements
  10 } from './selection-strategies-types.js'
  11
  12 /**
  13  * Selects the next worker with a fair share scheduling algorithm.
  14  * Loosely modeled after the fair queueing algorithm: https://en.wikipedia.org/wiki/Fair_queuing.
  15  *
  16  * @typeParam Worker - Type of worker which manages the strategy.
  17  * @typeParam Data - Type of data sent to the worker. This can only be structured-cloneable data.
  18  * @typeParam Response - Type of execution response. This can only be structured-cloneable data.
  19  */
  20 export class FairShareWorkerChoiceStrategy<
  21     Worker extends IWorker,
  22     Data = unknown,
  23     Response = unknown
  24   >
  25   extends AbstractWorkerChoiceStrategy<Worker, Data, Response>
  26   implements IWorkerChoiceStrategy {
  27   /** @inheritDoc */
  28   public readonly taskStatisticsRequirements: TaskStatisticsRequirements = {
  29     runTime: {
  30       aggregate: true,
  31       average: true,
  32       median: false
  33     },
  34     waitTime: DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS,
  35     elu: {
  36       aggregate: true,
  37       average: true,
  38       median: false
  39     }
  40   }
  41
  42   /** @inheritDoc */
  43   public constructor (
  44     pool: IPool<Worker, Data, Response>,
  45     opts: InternalWorkerChoiceStrategyOptions
  46   ) {
  47     super(pool, opts)
  48     this.setTaskStatisticsRequirements(this.opts)
  49   }
  50
  51   /** @inheritDoc */
  52   public reset (): boolean {
  53     for (const workerNode of this.pool.workerNodes) {
  54       delete workerNode.strategyData?.virtualTaskEndTimestamp
  55     }
  56     return true
  57   }
  58
  59   /** @inheritDoc */
  60   public update (workerNodeKey: number): boolean {
  61     this.pool.workerNodes[workerNodeKey].strategyData = {
  62       virtualTaskEndTimestamp:
  63         this.computeWorkerNodeVirtualTaskEndTimestamp(workerNodeKey)
  64     }
  65     return true
  66   }
  67
  68   /** @inheritDoc */
  69   public choose (): number | undefined {
  70     this.setPreviousWorkerNodeKey(this.nextWorkerNodeKey)
  71     this.nextWorkerNodeKey = this.fairShareNextWorkerNodeKey()
  72     return this.nextWorkerNodeKey
  73   }
  74
  75   /** @inheritDoc */
  76   public remove (): boolean {
  77     return true
  78   }
  79
  80   private fairShareNextWorkerNodeKey (): number | undefined {
  81     return this.pool.workerNodes.reduce(
  82       (minWorkerNodeKey, workerNode, workerNodeKey, workerNodes) => {
  83         if (workerNode.strategyData?.virtualTaskEndTimestamp == null) {
  84           workerNode.strategyData = {
  85             virtualTaskEndTimestamp:
  86               this.computeWorkerNodeVirtualTaskEndTimestamp(workerNodeKey)
  87           }
  88         }
  89         return this.isWorkerNodeReady(workerNodeKey) &&
  90           (workerNode.strategyData.virtualTaskEndTimestamp as number) <
  91             ((workerNodes[minWorkerNodeKey].strategyData as StrategyData)
  92               .virtualTaskEndTimestamp as number)
  93           ? workerNodeKey
  94           : minWorkerNodeKey
  95       },
  96       0
  97     )
  98   }
  99
 100   /**
 101    * Computes the worker node key virtual task end timestamp.
 102    *
 103    * @param workerNodeKey - The worker node key.
 104    * @returns The worker node key virtual task end timestamp.
 105    */
 106   private computeWorkerNodeVirtualTaskEndTimestamp (
 107     workerNodeKey: number
 108   ): number {
 109     return this.getWorkerNodeVirtualTaskEndTimestamp(
 110       workerNodeKey,
 111       this.getWorkerNodeVirtualTaskStartTimestamp(workerNodeKey)
 112     )
 113   }
 114
 115   private getWorkerNodeVirtualTaskEndTimestamp (
 116     workerNodeKey: number,
 117     workerNodeVirtualTaskStartTimestamp: number
 118   ): number {
 119     const workerNodeTaskRunTime =
 120       this.opts.measurement === Measurements.elu
 121         ? this.getWorkerNodeTaskElu(workerNodeKey)
 122         : this.getWorkerNodeTaskRunTime(workerNodeKey)
 123     return workerNodeVirtualTaskStartTimestamp + workerNodeTaskRunTime
 124   }
 125
 126   private getWorkerNodeVirtualTaskStartTimestamp (
 127     workerNodeKey: number
 128   ): number {
 129     const virtualTaskEndTimestamp =
 130       this.pool.workerNodes[workerNodeKey]?.strategyData
 131         ?.virtualTaskEndTimestamp
 132     const now = performance.now()
 133     return now < (virtualTaskEndTimestamp ?? -Infinity)
 134       ? (virtualTaskEndTimestamp as number)
 135       : now
 136   }
 137 }