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     return this.fairShareNextWorkerNodeKey()
  74   }
  75
  76   /** @inheritDoc */
  77   public remove (workerNodeKey: number): boolean {
  78     this.workersVirtualTaskEndTimestamp.splice(workerNodeKey, 1)
  79     return true
  80   }
  81
  82   private fairShareNextWorkerNodeKey (): number {
  83     let minWorkerVirtualTaskEndTimestamp = Infinity
  84     for (const [workerNodeKey] of this.pool.workerNodes.entries()) {
  85       if (this.workersVirtualTaskEndTimestamp[workerNodeKey] == null) {
  86         this.computeWorkerVirtualTaskEndTimestamp(workerNodeKey)
  87       }
  88       const workerVirtualTaskEndTimestamp =
  89         this.workersVirtualTaskEndTimestamp[workerNodeKey]
  90       if (
  91         this.isWorkerNodeEligible(workerNodeKey) &&
  92         workerVirtualTaskEndTimestamp < minWorkerVirtualTaskEndTimestamp
  93       ) {
  94         minWorkerVirtualTaskEndTimestamp = workerVirtualTaskEndTimestamp
  95         this.nextWorkerNodeKey = workerNodeKey
  96       }
  97     }
  98     return this.nextWorkerNodeKey
  99   }
 100
 101   /**
 102    * Computes the worker node key virtual task end timestamp.
 103    *
 104    * @param workerNodeKey - The worker node key.
 105    */
 106   private computeWorkerVirtualTaskEndTimestamp (workerNodeKey: number): void {
 107     this.workersVirtualTaskEndTimestamp[workerNodeKey] =
 108       this.getWorkerVirtualTaskEndTimestamp(
 109         workerNodeKey,
 110         this.getWorkerVirtualTaskStartTimestamp(workerNodeKey)
 111       )
 112   }
 113
 114   private getWorkerVirtualTaskEndTimestamp (
 115     workerNodeKey: number,
 116     workerVirtualTaskStartTimestamp: number
 117   ): number {
 118     const workerTaskRunTime =
 119       this.opts.measurement === Measurements.elu
 120         ? this.getWorkerTaskElu(workerNodeKey)
 121         : this.getWorkerTaskRunTime(workerNodeKey)
 122     return workerVirtualTaskStartTimestamp + workerTaskRunTime
 123   }
 124
 125   private getWorkerVirtualTaskStartTimestamp (workerNodeKey: number): number {
 126     return Math.max(
 127       performance.now(),
 128       this.workersVirtualTaskEndTimestamp[workerNodeKey] ?? -Infinity
 129     )
 130   }
 131 }