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_MEASUREMENT_STATISTICS_REQUIREMENTS } from '../../utils'
   4 import { AbstractWorkerChoiceStrategy } from './abstract-worker-choice-strategy'
   5 import type {
   6   IWorkerChoiceStrategy,
   7   InternalWorkerChoiceStrategyOptions,
   8   TaskStatisticsRequirements
   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 structured-cloneable data.
  17  * @typeParam Response - Type of execution response. This can only be structured-cloneable 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: DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS,
  34     elu: DEFAULT_MEASUREMENT_STATISTICS_REQUIREMENTS
  35   }
  36
  37   /**
  38    * Default worker weight.
  39    */
  40   private readonly defaultWorkerWeight: number
  41   /**
  42    * Worker node virtual task runtime.
  43    */
  44   private workerNodeVirtualTaskRunTime: number = 0
  45
  46   /** @inheritDoc */
  47   public constructor (
  48     pool: IPool<Worker, Data, Response>,
  49     opts: InternalWorkerChoiceStrategyOptions
  50   ) {
  51     super(pool, opts)
  52     this.setTaskStatisticsRequirements(this.opts)
  53     this.defaultWorkerWeight = this.computeDefaultWorkerWeight()
  54   }
  55
  56   /** @inheritDoc */
  57   public reset (): boolean {
  58     this.resetWorkerNodeKeyProperties()
  59     this.workerNodeVirtualTaskRunTime = 0
  60     return true
  61   }
  62
  63   /** @inheritDoc */
  64   public update (): boolean {
  65     return true
  66   }
  67
  68   /** @inheritDoc */
  69   public choose (): number | undefined {
  70     this.setPreviousWorkerNodeKey(this.nextWorkerNodeKey)
  71     this.weightedRoundRobinNextWorkerNodeKey()
  72     this.checkNextWorkerNodeReadiness()
  73     return this.nextWorkerNodeKey
  74   }
  75
  76   /** @inheritDoc */
  77   public remove (workerNodeKey: number): boolean {
  78     if (this.pool.workerNodes.length === 0) {
  79       this.reset()
  80     }
  81     if (this.nextWorkerNodeKey === workerNodeKey) {
  82       this.workerNodeVirtualTaskRunTime = 0
  83       if (this.nextWorkerNodeKey > this.pool.workerNodes.length - 1) {
  84         this.nextWorkerNodeKey = this.pool.workerNodes.length - 1
  85       }
  86     }
  87     if (
  88       this.previousWorkerNodeKey === workerNodeKey &&
  89       this.previousWorkerNodeKey > this.pool.workerNodes.length - 1
  90     ) {
  91       this.previousWorkerNodeKey = this.pool.workerNodes.length - 1
  92     }
  93     return true
  94   }
  95
  96   private weightedRoundRobinNextWorkerNodeKey (): number | undefined {
  97     const workerWeight =
  98       this.opts.weights?.[
  99         this.nextWorkerNodeKey ?? this.previousWorkerNodeKey
 100       ] ?? this.defaultWorkerWeight
 101     if (this.workerNodeVirtualTaskRunTime < workerWeight) {
 102       this.workerNodeVirtualTaskRunTime =
 103         this.workerNodeVirtualTaskRunTime +
 104         this.getWorkerNodeTaskRunTime(
 105           this.nextWorkerNodeKey ?? this.previousWorkerNodeKey
 106         )
 107     } else {
 108       this.nextWorkerNodeKey =
 109         this.nextWorkerNodeKey === this.pool.workerNodes.length - 1
 110           ? 0
 111           : (this.nextWorkerNodeKey ?? this.previousWorkerNodeKey) + 1
 112       this.workerNodeVirtualTaskRunTime = 0
 113     }
 114     return this.nextWorkerNodeKey
 115   }
 116 }