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