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 } 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           // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
  91           workerNode.strategyData.virtualTaskEndTimestamp! <
  92             // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
  93             workerNodes[minWorkerNodeKey].strategyData!.virtualTaskEndTimestamp!
  94           ? workerNodeKey
  95           : minWorkerNodeKey
  96       },
  97       0
  98     )
  99   }
 100
 101   /**
 102    * Computes the worker node key virtual task end timestamp.
 103    *
 104    * @param workerNodeKey - The worker node key.
 105    * @returns The worker node key virtual task end timestamp.
 106    */
 107   private computeWorkerNodeVirtualTaskEndTimestamp (
 108     workerNodeKey: number
 109   ): number {
 110     return this.getWorkerNodeVirtualTaskEndTimestamp(
 111       workerNodeKey,
 112       this.getWorkerNodeVirtualTaskStartTimestamp(workerNodeKey)
 113     )
 114   }
 115
 116   private getWorkerNodeVirtualTaskEndTimestamp (
 117     workerNodeKey: number,
 118     workerNodeVirtualTaskStartTimestamp: number
 119   ): number {
 120     const workerNodeTaskRunTime =
 121       this.opts.measurement === Measurements.elu
 122         ? this.getWorkerNodeTaskElu(workerNodeKey)
 123         : this.getWorkerNodeTaskRunTime(workerNodeKey)
 124     return workerNodeVirtualTaskStartTimestamp + workerNodeTaskRunTime
 125   }
 126
 127   private getWorkerNodeVirtualTaskStartTimestamp (
 128     workerNodeKey: number
 129   ): number {
 130     const virtualTaskEndTimestamp =
 131       this.pool.workerNodes[workerNodeKey]?.strategyData
 132         ?.virtualTaskEndTimestamp
 133     const now = performance.now()
 134     return now < (virtualTaskEndTimestamp ?? -Infinity)
 135       ? // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
 136       virtualTaskEndTimestamp!
 137       : now
 138   }
 139 }