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

   1 import type { IPool } from '../pool.js'
   2 import type { IWorker } from '../worker.js'
   3 import { AbstractWorkerChoiceStrategy } from './abstract-worker-choice-strategy.js'
   4 import {
   5   type IWorkerChoiceStrategy,
   6   Measurements,
   7   type TaskStatisticsRequirements,
   8   type WorkerChoiceStrategyOptions
   9 } from './selection-strategies-types.js'
  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 structured-cloneable data.
  17  * @typeParam Response - Type of execution response. This can only be structured-cloneable 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 taskStatisticsRequirements: TaskStatisticsRequirements = {
  28     runTime: {
  29       aggregate: true,
  30       average: true,
  31       median: false
  32     },
  33     waitTime: {
  34       aggregate: true,
  35       average: true,
  36       median: false
  37     },
  38     elu: {
  39       aggregate: true,
  40       average: true,
  41       median: false
  42     }
  43   }
  44
  45   /** @inheritDoc */
  46   public constructor (
  47     pool: IPool<Worker, Data, Response>,
  48     opts?: WorkerChoiceStrategyOptions
  49   ) {
  50     super(pool, opts)
  51     this.setTaskStatisticsRequirements(this.opts)
  52   }
  53
  54   /** @inheritDoc */
  55   public reset (): boolean {
  56     for (const workerNode of this.pool.workerNodes) {
  57       delete workerNode.strategyData?.virtualTaskEndTimestamp
  58     }
  59     return true
  60   }
  61
  62   /** @inheritDoc */
  63   public update (workerNodeKey: number): boolean {
  64     this.pool.workerNodes[workerNodeKey].strategyData = {
  65       virtualTaskEndTimestamp:
  66         this.computeWorkerNodeVirtualTaskEndTimestamp(workerNodeKey)
  67     }
  68     return true
  69   }
  70
  71   /** @inheritDoc */
  72   public choose (): number | undefined {
  73     this.setPreviousWorkerNodeKey(this.nextWorkerNodeKey)
  74     this.nextWorkerNodeKey = this.fairShareNextWorkerNodeKey()
  75     return this.nextWorkerNodeKey
  76   }
  77
  78   /** @inheritDoc */
  79   public remove (): boolean {
  80     return true
  81   }
  82
  83   private fairShareNextWorkerNodeKey (): number | undefined {
  84     return this.pool.workerNodes.reduce(
  85       (minWorkerNodeKey, workerNode, workerNodeKey, workerNodes) => {
  86         if (workerNode.strategyData?.virtualTaskEndTimestamp == null) {
  87           workerNode.strategyData = {
  88             virtualTaskEndTimestamp:
  89               this.computeWorkerNodeVirtualTaskEndTimestamp(workerNodeKey)
  90           }
  91         }
  92         return this.isWorkerNodeReady(workerNodeKey) &&
  93           // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
  94           workerNode.strategyData.virtualTaskEndTimestamp! <
  95             // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
  96             workerNodes[minWorkerNodeKey].strategyData!.virtualTaskEndTimestamp!
  97           ? workerNodeKey
  98           : minWorkerNodeKey
  99       },
 100       0
 101     )
 102   }
 103
 104   /**
 105    * Computes the worker node key virtual task end timestamp.
 106    *
 107    * @param workerNodeKey - The worker node key.
 108    * @returns The worker node key virtual task end timestamp.
 109    */
 110   private computeWorkerNodeVirtualTaskEndTimestamp (
 111     workerNodeKey: number
 112   ): number {
 113     return this.getWorkerNodeVirtualTaskEndTimestamp(
 114       workerNodeKey,
 115       this.getWorkerNodeVirtualTaskStartTimestamp(workerNodeKey)
 116     )
 117   }
 118
 119   private getWorkerNodeVirtualTaskEndTimestamp (
 120     workerNodeKey: number,
 121     workerNodeVirtualTaskStartTimestamp: number
 122   ): number {
 123     const workerNodeTaskExecutionTime =
 124       this.getWorkerNodeTaskWaitTime(workerNodeKey) +
 125       // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
 126       (this.opts!.measurement === Measurements.elu
 127         ? this.getWorkerNodeTaskElu(workerNodeKey)
 128         : this.getWorkerNodeTaskRunTime(workerNodeKey))
 129     return workerNodeVirtualTaskStartTimestamp + workerNodeTaskExecutionTime
 130   }
 131
 132   private getWorkerNodeVirtualTaskStartTimestamp (
 133     workerNodeKey: number
 134   ): number {
 135     const virtualTaskEndTimestamp =
 136       this.pool.workerNodes[workerNodeKey]?.strategyData
 137         ?.virtualTaskEndTimestamp
 138     const now = performance.now()
 139     return now < (virtualTaskEndTimestamp ?? -Infinity)
 140       ? // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
 141       virtualTaskEndTimestamp!
 142       : now
 143   }
 144 }