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

   1 import type { IWorker } from '../worker'
   2 import type { IPool } from '../pool'
   3 import {
   4   DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS,
   5   DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS
   6 } from '../../utils'
   7 import { AbstractWorkerChoiceStrategy } from './abstract-worker-choice-strategy'
   8 import type {
   9   IWorkerChoiceStrategy,
  10   StrategyPolicy,
  11   TaskStatisticsRequirements,
  12   WorkerChoiceStrategyOptions
  13 } from './selection-strategies-types'
  14
  15 /**
  16  * Selects the next worker with a weighted round robin scheduling algorithm.
  17  * Loosely modeled after the weighted round robin queueing algorithm: https://en.wikipedia.org/wiki/Weighted_round_robin.
  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 WeightedRoundRobinWorkerChoiceStrategy<
  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 strategyPolicy: StrategyPolicy = {
  32     dynamicWorkerUsage: false,
  33     dynamicWorkerReady: true
  34   }
  35
  36   /** @inheritDoc */
  37   public readonly taskStatisticsRequirements: TaskStatisticsRequirements = {
  38     runTime: {
  39       aggregate: true,
  40       average: true,
  41       median: false
  42     },
  43     waitTime: DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS,
  44     elu: DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS
  45   }
  46
  47   /**
  48    * Default worker weight.
  49    */
  50   private readonly defaultWorkerWeight: number
  51   /**
  52    * Worker virtual task runtime.
  53    */
  54   private workerVirtualTaskRunTime: number = 0
  55
  56   /** @inheritDoc */
  57   public constructor (
  58     pool: IPool<Worker, Data, Response>,
  59     opts: WorkerChoiceStrategyOptions = DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS
  60   ) {
  61     super(pool, opts)
  62     this.setTaskStatisticsRequirements(this.opts)
  63     this.defaultWorkerWeight = this.computeDefaultWorkerWeight()
  64   }
  65
  66   /** @inheritDoc */
  67   public reset (): boolean {
  68     this.nextWorkerNodeKey = 0
  69     this.workerVirtualTaskRunTime = 0
  70     return true
  71   }
  72
  73   /** @inheritDoc */
  74   public update (): boolean {
  75     return true
  76   }
  77
  78   /** @inheritDoc */
  79   public choose (): number | undefined {
  80     const chosenWorkerNodeKey = this.nextWorkerNodeKey
  81     this.weightedRoundRobinNextWorkerNodeKey()
  82     if (!this.isWorkerNodeEligible(this.nextWorkerNodeKey as number)) {
  83       this.nextWorkerNodeKey = undefined
  84     }
  85     return chosenWorkerNodeKey
  86   }
  87
  88   /** @inheritDoc */
  89   public remove (workerNodeKey: number): boolean {
  90     if (this.nextWorkerNodeKey === workerNodeKey) {
  91       if (this.pool.workerNodes.length === 0) {
  92         this.nextWorkerNodeKey = 0
  93       } else if (this.nextWorkerNodeKey > this.pool.workerNodes.length - 1) {
  94         this.nextWorkerNodeKey = this.pool.workerNodes.length - 1
  95       }
  96       this.workerVirtualTaskRunTime = 0
  97     }
  98     return true
  99   }
 100
 101   private weightedRoundRobinNextWorkerNodeKey (): number | undefined {
 102     const workerVirtualTaskRunTime = this.workerVirtualTaskRunTime
 103     const workerWeight =
 104       this.opts.weights?.[this.nextWorkerNodeKey ?? 0] ??
 105       this.defaultWorkerWeight
 106     if (workerVirtualTaskRunTime < workerWeight) {
 107       this.workerVirtualTaskRunTime =
 108         workerVirtualTaskRunTime +
 109         this.getWorkerTaskRunTime(this.nextWorkerNodeKey ?? 0)
 110     } else {
 111       this.nextWorkerNodeKey =
 112         this.nextWorkerNodeKey === this.pool.workerNodes.length - 1
 113           ? 0
 114           : (this.nextWorkerNodeKey ?? 0) + 1
 115       this.workerVirtualTaskRunTime = 0
 116     }
 117     return this.nextWorkerNodeKey
 118   }
 119 }