src/pools/selection-strategies/weighted-round-robin-worker-choice-strategy.ts

   1 import { cpus } from 'node:os'
   2 import type { IPoolInternal } from '../pool-internal'
   3 import type { IPoolWorker } from '../pool-worker'
   4 import { AbstractWorkerChoiceStrategy } from './abstract-worker-choice-strategy'
   5 import type {
   6   IWorkerChoiceStrategy,
   7   RequiredStatistics
   8 } from './selection-strategies-types'
   9
  10 /**
  11  * Virtual task runtime.
  12  */
  13 interface TaskRunTime {
  14   weight: number
  15   runTime: number
  16 }
  17
  18 /**
  19  * Selects the next worker with a weighted round robin scheduling algorithm.
  20  * Loosely modeled after the weighted round robin queueing algorithm: https://en.wikipedia.org/wiki/Weighted_round_robin.
  21  *
  22  * @typeParam Worker - Type of worker which manages the strategy.
  23  * @typeParam Data - Type of data sent to the worker. This can only be serializable data.
  24  * @typeParam Response - Type of response of execution. This can only be serializable data.
  25  */
  26 export class WeightedRoundRobinWorkerChoiceStrategy<
  27     Worker extends IPoolWorker,
  28     Data,
  29     Response
  30   >
  31   extends AbstractWorkerChoiceStrategy<Worker, Data, Response>
  32   implements IWorkerChoiceStrategy {
  33   /** {@inheritDoc} */
  34   public readonly requiredStatistics: RequiredStatistics = {
  35     runTime: true,
  36     avgRunTime: true
  37   }
  38
  39   /**
  40    * Worker id where the current task will be submitted.
  41    */
  42   private currentWorkerId: number = 0
  43   /**
  44    * Default worker weight.
  45    */
  46   private readonly defaultWorkerWeight: number
  47   /**
  48    * Per worker virtual task runtime map.
  49    */
  50   private readonly workersTaskRunTime: Map<number, TaskRunTime> = new Map<
  51   number,
  52   TaskRunTime
  53   >()
  54
  55   /**
  56    * Constructs a worker choice strategy that selects with a weighted round robin scheduling algorithm.
  57    *
  58    * @param pool - The pool instance.
  59    */
  60   public constructor (pool: IPoolInternal<Worker, Data, Response>) {
  61     super(pool)
  62     this.defaultWorkerWeight = this.computeWorkerWeight()
  63     this.initWorkersTaskRunTime()
  64   }
  65
  66   /** {@inheritDoc} */
  67   public reset (): boolean {
  68     this.currentWorkerId = 0
  69     this.workersTaskRunTime.clear()
  70     this.initWorkersTaskRunTime()
  71     return true
  72   }
  73
  74   /** {@inheritDoc} */
  75   public choose (): number {
  76     const chosenWorkerKey = this.currentWorkerId
  77     if (this.isDynamicPool && !this.workersTaskRunTime.has(chosenWorkerKey)) {
  78       this.initWorkerTaskRunTime(chosenWorkerKey)
  79     }
  80     const workerTaskRunTime =
  81       this.workersTaskRunTime.get(chosenWorkerKey)?.runTime ?? 0
  82     const workerTaskWeight =
  83       this.workersTaskRunTime.get(chosenWorkerKey)?.weight ??
  84       this.defaultWorkerWeight
  85     if (workerTaskRunTime < workerTaskWeight) {
  86       this.setWorkerTaskRunTime(
  87         chosenWorkerKey,
  88         workerTaskWeight,
  89         workerTaskRunTime +
  90           (this.getWorkerVirtualTaskRunTime(chosenWorkerKey) ?? 0)
  91       )
  92     } else {
  93       this.currentWorkerId =
  94         this.currentWorkerId === this.pool.workers.length - 1
  95           ? 0
  96           : this.currentWorkerId + 1
  97       this.setWorkerTaskRunTime(this.currentWorkerId, workerTaskWeight, 0)
  98     }
  99     return chosenWorkerKey
 100   }
 101
 102   /** {@inheritDoc} */
 103   public remove (workerKey: number): boolean {
 104     if (this.currentWorkerId === workerKey) {
 105       this.currentWorkerId =
 106         this.currentWorkerId > this.pool.workers.length - 1
 107           ? this.pool.workers.length - 1
 108           : this.currentWorkerId
 109     }
 110     const workerDeleted = this.workersTaskRunTime.delete(workerKey)
 111     for (const [key, value] of this.workersTaskRunTime) {
 112       if (key > workerKey) {
 113         this.workersTaskRunTime.set(key - 1, value)
 114       }
 115     }
 116     return workerDeleted
 117   }
 118
 119   private initWorkersTaskRunTime (): void {
 120     for (const [index] of this.pool.workers.entries()) {
 121       this.initWorkerTaskRunTime(index)
 122     }
 123   }
 124
 125   private initWorkerTaskRunTime (workerKey: number): void {
 126     this.setWorkerTaskRunTime(workerKey, this.defaultWorkerWeight, 0)
 127   }
 128
 129   private setWorkerTaskRunTime (
 130     workerKey: number,
 131     weight: number,
 132     runTime: number
 133   ): void {
 134     this.workersTaskRunTime.set(workerKey, {
 135       weight,
 136       runTime
 137     })
 138   }
 139
 140   private getWorkerVirtualTaskRunTime (workerKey: number): number {
 141     return this.pool.workers[workerKey].tasksUsage.avgRunTime
 142   }
 143
 144   private computeWorkerWeight (): number {
 145     let cpusCycleTimeWeight = 0
 146     for (const cpu of cpus()) {
 147       // CPU estimated cycle time
 148       const numberOfDigits = cpu.speed.toString().length - 1
 149       const cpuCycleTime = 1 / (cpu.speed / Math.pow(10, numberOfDigits))
 150       cpusCycleTimeWeight += cpuCycleTime * Math.pow(10, numberOfDigits)
 151     }
 152     return Math.round(cpusCycleTimeWeight / cpus().length)
 153   }
 154 }