fix: fix race condition in worker choice strategies

[poolifier.git] / src / pools / selection-strategies / round-robin-worker-choice-strategy.ts

import { DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS } from '../../utils'
import type { IPool } from '../pool'
import type { IWorker } from '../worker'
import { AbstractWorkerChoiceStrategy } from './abstract-worker-choice-strategy'
import type {
  IWorkerChoiceStrategy,
  WorkerChoiceStrategyOptions
} from './selection-strategies-types'

/**
 * Selects the next worker in a round robin fashion.
 *
 * @typeParam Worker - Type of worker which manages the strategy.
 * @typeParam Data - Type of data sent to the worker. This can only be structured-cloneable data.
 * @typeParam Response - Type of execution response. This can only be structured-cloneable data.
 */
export class RoundRobinWorkerChoiceStrategy<
    Worker extends IWorker,
    Data = unknown,
    Response = unknown
  >
  extends AbstractWorkerChoiceStrategy<Worker, Data, Response>
  implements IWorkerChoiceStrategy {
  /** @inheritDoc */
  public constructor (
    pool: IPool<Worker, Data, Response>,
    opts: WorkerChoiceStrategyOptions = DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS
  ) {
    super(pool, opts)
    this.setTaskStatisticsRequirements(this.opts)
  }

  /** @inheritDoc */
  public reset (): boolean {
    this.resetWorkerNodeKeyProperties()
    return true
  }

  /** @inheritDoc */
  public update (): boolean {
    return true
  }

  /** @inheritDoc */
  public choose (): number | undefined {
    const chosenWorkerNodeKey = this.nextWorkerNodeKey
    this.roundRobinNextWorkerNodeKey()
    return chosenWorkerNodeKey
  }

  /** @inheritDoc */
  public remove (workerNodeKey: number): boolean {
    if (this.nextWorkerNodeKey === workerNodeKey) {
      if (this.pool.workerNodes.length === 0) {
        this.nextWorkerNodeKey = 0
      } else if (this.nextWorkerNodeKey > this.pool.workerNodes.length - 1) {
        this.nextWorkerNodeKey = this.pool.workerNodes.length - 1
      }
    }
    return true
  }

  private roundRobinNextWorkerNodeKey (): number | undefined {
    this.nextWorkerNodeKey =
      this.nextWorkerNodeKey === this.pool.workerNodes.length - 1
        ? 0
        : (this.nextWorkerNodeKey ?? this.previousWorkerNodeKey) + 1
    return this.nextWorkerNodeKey
  }
}