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