fix: remove wrong bound for event handlers
[poolifier.git] / src / pools / abstract-pool.ts
index e122e88180bce90a32710f0d8f6bd8537d57b8b9..a0fc76c371584d3e69855fe732d720db482cc0bf 100644 (file)
@@ -1,7 +1,7 @@
 import { randomUUID } from 'node:crypto'
 import { performance } from 'node:perf_hooks'
-import { existsSync } from 'node:fs'
-import { type TransferListItem } from 'node:worker_threads'
+import type { TransferListItem } from 'node:worker_threads'
+import { EventEmitterAsyncResource } from 'node:events'
 import type {
   MessageValue,
   PromiseResponseWrapper,
@@ -17,14 +17,12 @@ import {
   max,
   median,
   min,
-  round,
-  updateMeasurementStatistics
+  round
 } from '../utils'
 import { KillBehaviors } from '../worker/worker-options'
 import type { TaskFunction } from '../worker/task-functions'
 import {
   type IPool,
-  PoolEmitter,
   PoolEvents,
   type PoolInfo,
   type PoolOptions,
@@ -36,6 +34,7 @@ import type {
   IWorker,
   IWorkerNode,
   WorkerInfo,
+  WorkerNodeEventDetail,
   WorkerType,
   WorkerUsage
 } from './worker'
@@ -49,6 +48,12 @@ import {
 import { WorkerChoiceStrategyContext } from './selection-strategies/worker-choice-strategy-context'
 import { version } from './version'
 import { WorkerNode } from './worker-node'
+import {
+  checkFilePath,
+  checkValidTasksQueueOptions,
+  checkValidWorkerChoiceStrategy,
+  updateMeasurementStatistics
+} from './utils'
 
 /**
  * Base class that implements some shared logic for all poolifier pools.
@@ -66,7 +71,12 @@ export abstract class AbstractPool<
   public readonly workerNodes: Array<IWorkerNode<Worker, Data>> = []
 
   /** @inheritDoc */
-  public readonly emitter?: PoolEmitter
+  public emitter?: EventEmitterAsyncResource
+
+  /**
+   * Dynamic pool maximum size property placeholder.
+   */
+  protected readonly max?: number
 
   /**
    * The task execution response promise map:
@@ -87,11 +97,6 @@ export abstract class AbstractPool<
   Response
   >
 
-  /**
-   * Dynamic pool maximum size property placeholder.
-   */
-  protected readonly max?: number
-
   /**
    * The task functions added at runtime map:
    * - `key`: The task function name.
@@ -99,14 +104,14 @@ export abstract class AbstractPool<
    */
   private readonly taskFunctions: Map<string, TaskFunction<Data, Response>>
 
-  /**
-   * Whether the pool is starting or not.
-   */
-  private readonly starting: boolean
   /**
    * Whether the pool is started or not.
    */
   private started: boolean
+  /**
+   * Whether the pool is starting or not.
+   */
+  private starting: boolean
   /**
    * The start timestamp of the pool.
    */
@@ -129,8 +134,8 @@ export abstract class AbstractPool<
         'Cannot start a pool from a worker with the same type as the pool'
       )
     }
+    checkFilePath(this.filePath)
     this.checkNumberOfWorkers(this.numberOfWorkers)
-    this.checkFilePath(this.filePath)
     this.checkPoolOptions(this.opts)
 
     this.chooseWorkerNode = this.chooseWorkerNode.bind(this)
@@ -138,7 +143,7 @@ export abstract class AbstractPool<
     this.enqueueTask = this.enqueueTask.bind(this)
 
     if (this.opts.enableEvents === true) {
-      this.emitter = new PoolEmitter()
+      this.initializeEventEmitter()
     }
     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext<
     Worker,
@@ -154,27 +159,15 @@ export abstract class AbstractPool<
 
     this.taskFunctions = new Map<string, TaskFunction<Data, Response>>()
 
-    this.starting = true
-    this.startPool()
+    this.started = false
     this.starting = false
-    this.started = true
+    if (this.opts.startWorkers === true) {
+      this.start()
+    }
 
     this.startTimestamp = performance.now()
   }
 
-  private checkFilePath (filePath: string): void {
-    if (
-      filePath == null ||
-      typeof filePath !== 'string' ||
-      (typeof filePath === 'string' && filePath.trim().length === 0)
-    ) {
-      throw new Error('Please specify a file with a worker implementation')
-    }
-    if (!existsSync(filePath)) {
-      throw new Error(`Cannot find the worker file '${filePath}'`)
-    }
-  }
-
   private checkNumberOfWorkers (numberOfWorkers: number): void {
     if (numberOfWorkers == null) {
       throw new Error(
@@ -193,51 +186,26 @@ export abstract class AbstractPool<
     }
   }
 
-  protected checkDynamicPoolSize (min: number, max: number): void {
-    if (this.type === PoolTypes.dynamic) {
-      if (max == null) {
-        throw new TypeError(
-          'Cannot instantiate a dynamic pool without specifying the maximum pool size'
-        )
-      } else if (!Number.isSafeInteger(max)) {
-        throw new TypeError(
-          'Cannot instantiate a dynamic pool with a non safe integer maximum pool size'
-        )
-      } else if (min > max) {
-        throw new RangeError(
-          'Cannot instantiate a dynamic pool with a maximum pool size inferior to the minimum pool size'
-        )
-      } else if (max === 0) {
-        throw new RangeError(
-          'Cannot instantiate a dynamic pool with a maximum pool size equal to zero'
-        )
-      } else if (min === max) {
-        throw new RangeError(
-          'Cannot instantiate a dynamic pool with a minimum pool size equal to the maximum pool size. Use a fixed pool instead'
-        )
-      }
-    }
-  }
-
   private checkPoolOptions (opts: PoolOptions<Worker>): void {
     if (isPlainObject(opts)) {
+      this.opts.startWorkers = opts.startWorkers ?? true
+      checkValidWorkerChoiceStrategy(
+        opts.workerChoiceStrategy as WorkerChoiceStrategy
+      )
       this.opts.workerChoiceStrategy =
         opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
-      this.checkValidWorkerChoiceStrategy(this.opts.workerChoiceStrategy)
+      this.checkValidWorkerChoiceStrategyOptions(
+        opts.workerChoiceStrategyOptions as WorkerChoiceStrategyOptions
+      )
       this.opts.workerChoiceStrategyOptions = {
         ...DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS,
         ...opts.workerChoiceStrategyOptions
       }
-      this.checkValidWorkerChoiceStrategyOptions(
-        this.opts.workerChoiceStrategyOptions
-      )
       this.opts.restartWorkerOnError = opts.restartWorkerOnError ?? true
       this.opts.enableEvents = opts.enableEvents ?? true
       this.opts.enableTasksQueue = opts.enableTasksQueue ?? false
       if (this.opts.enableTasksQueue) {
-        this.checkValidTasksQueueOptions(
-          opts.tasksQueueOptions as TasksQueueOptions
-        )
+        checkValidTasksQueueOptions(opts.tasksQueueOptions as TasksQueueOptions)
         this.opts.tasksQueueOptions = this.buildTasksQueueOptions(
           opts.tasksQueueOptions as TasksQueueOptions
         )
@@ -247,26 +215,19 @@ export abstract class AbstractPool<
     }
   }
 
-  private checkValidWorkerChoiceStrategy (
-    workerChoiceStrategy: WorkerChoiceStrategy
-  ): void {
-    if (!Object.values(WorkerChoiceStrategies).includes(workerChoiceStrategy)) {
-      throw new Error(
-        `Invalid worker choice strategy '${workerChoiceStrategy}'`
-      )
-    }
-  }
-
   private checkValidWorkerChoiceStrategyOptions (
     workerChoiceStrategyOptions: WorkerChoiceStrategyOptions
   ): void {
-    if (!isPlainObject(workerChoiceStrategyOptions)) {
+    if (
+      workerChoiceStrategyOptions != null &&
+      !isPlainObject(workerChoiceStrategyOptions)
+    ) {
       throw new TypeError(
         'Invalid worker choice strategy options: must be a plain object'
       )
     }
     if (
-      workerChoiceStrategyOptions.retries != null &&
+      workerChoiceStrategyOptions?.retries != null &&
       !Number.isSafeInteger(workerChoiceStrategyOptions.retries)
     ) {
       throw new TypeError(
@@ -274,7 +235,7 @@ export abstract class AbstractPool<
       )
     }
     if (
-      workerChoiceStrategyOptions.retries != null &&
+      workerChoiceStrategyOptions?.retries != null &&
       workerChoiceStrategyOptions.retries < 0
     ) {
       throw new RangeError(
@@ -282,7 +243,7 @@ export abstract class AbstractPool<
       )
     }
     if (
-      workerChoiceStrategyOptions.weights != null &&
+      workerChoiceStrategyOptions?.weights != null &&
       Object.keys(workerChoiceStrategyOptions.weights).length !== this.maxSize
     ) {
       throw new Error(
@@ -290,7 +251,7 @@ export abstract class AbstractPool<
       )
     }
     if (
-      workerChoiceStrategyOptions.measurement != null &&
+      workerChoiceStrategyOptions?.measurement != null &&
       !Object.values(Measurements).includes(
         workerChoiceStrategyOptions.measurement
       )
@@ -301,58 +262,10 @@ export abstract class AbstractPool<
     }
   }
 
-  private checkValidTasksQueueOptions (
-    tasksQueueOptions: TasksQueueOptions
-  ): void {
-    if (tasksQueueOptions != null && !isPlainObject(tasksQueueOptions)) {
-      throw new TypeError('Invalid tasks queue options: must be a plain object')
-    }
-    if (
-      tasksQueueOptions?.concurrency != null &&
-      !Number.isSafeInteger(tasksQueueOptions?.concurrency)
-    ) {
-      throw new TypeError(
-        'Invalid worker node tasks concurrency: must be an integer'
-      )
-    }
-    if (
-      tasksQueueOptions?.concurrency != null &&
-      tasksQueueOptions?.concurrency <= 0
-    ) {
-      throw new RangeError(
-        `Invalid worker node tasks concurrency: ${tasksQueueOptions?.concurrency} is a negative integer or zero`
-      )
-    }
-    if (tasksQueueOptions?.queueMaxSize != null) {
-      throw new Error(
-        'Invalid tasks queue options: queueMaxSize is deprecated, please use size instead'
-      )
-    }
-    if (
-      tasksQueueOptions?.size != null &&
-      !Number.isSafeInteger(tasksQueueOptions?.size)
-    ) {
-      throw new TypeError(
-        'Invalid worker node tasks queue size: must be an integer'
-      )
-    }
-    if (tasksQueueOptions?.size != null && tasksQueueOptions?.size <= 0) {
-      throw new RangeError(
-        `Invalid worker node tasks queue size: ${tasksQueueOptions?.size} is a negative integer or zero`
-      )
-    }
-  }
-
-  private startPool (): void {
-    while (
-      this.workerNodes.reduce(
-        (accumulator, workerNode) =>
-          !workerNode.info.dynamic ? accumulator + 1 : accumulator,
-        0
-      ) < this.numberOfWorkers
-    ) {
-      this.createAndSetupWorkerNode()
-    }
+  private initializeEventEmitter (): void {
+    this.emitter = new EventEmitterAsyncResource({
+      name: `poolifier:${this.type}-${this.worker}-pool`
+    })
   }
 
   /** @inheritDoc */
@@ -361,6 +274,7 @@ export abstract class AbstractPool<
       version,
       type: this.type,
       worker: this.worker,
+      started: this.started,
       ready: this.ready,
       strategy: this.opts.workerChoiceStrategy as WorkerChoiceStrategy,
       minSize: this.minSize,
@@ -578,7 +492,7 @@ export abstract class AbstractPool<
    * @param message - The received message.
    * @throws {@link https://nodejs.org/api/errors.html#class-error} If the worker id is invalid.
    */
-  private checkMessageWorkerId (message: MessageValue<Response>): void {
+  private checkMessageWorkerId (message: MessageValue<Data | Response>): void {
     if (message.workerId == null) {
       throw new Error('Worker message received without worker id')
     } else if (
@@ -620,7 +534,7 @@ export abstract class AbstractPool<
     workerChoiceStrategy: WorkerChoiceStrategy,
     workerChoiceStrategyOptions?: WorkerChoiceStrategyOptions
   ): void {
-    this.checkValidWorkerChoiceStrategy(workerChoiceStrategy)
+    checkValidWorkerChoiceStrategy(workerChoiceStrategy)
     this.opts.workerChoiceStrategy = workerChoiceStrategy
     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
       this.opts.workerChoiceStrategy
@@ -654,6 +568,8 @@ export abstract class AbstractPool<
     tasksQueueOptions?: TasksQueueOptions
   ): void {
     if (this.opts.enableTasksQueue === true && !enable) {
+      this.unsetTaskStealing()
+      this.unsetTasksStealingOnBackPressure()
       this.flushTasksQueues()
     }
     this.opts.enableTasksQueue = enable
@@ -663,33 +579,81 @@ export abstract class AbstractPool<
   /** @inheritDoc */
   public setTasksQueueOptions (tasksQueueOptions: TasksQueueOptions): void {
     if (this.opts.enableTasksQueue === true) {
-      this.checkValidTasksQueueOptions(tasksQueueOptions)
+      checkValidTasksQueueOptions(tasksQueueOptions)
       this.opts.tasksQueueOptions =
         this.buildTasksQueueOptions(tasksQueueOptions)
       this.setTasksQueueSize(this.opts.tasksQueueOptions.size as number)
+      if (this.opts.tasksQueueOptions.taskStealing === true) {
+        this.setTaskStealing()
+      } else {
+        this.unsetTaskStealing()
+      }
+      if (this.opts.tasksQueueOptions.tasksStealingOnBackPressure === true) {
+        this.setTasksStealingOnBackPressure()
+      } else {
+        this.unsetTasksStealingOnBackPressure()
+      }
     } else if (this.opts.tasksQueueOptions != null) {
       delete this.opts.tasksQueueOptions
     }
   }
 
-  private setTasksQueueSize (size: number): void {
-    for (const workerNode of this.workerNodes) {
-      workerNode.tasksQueueBackPressureSize = size
-    }
-  }
-
   private buildTasksQueueOptions (
     tasksQueueOptions: TasksQueueOptions
   ): TasksQueueOptions {
     return {
       ...{
         size: Math.pow(this.maxSize, 2),
-        concurrency: 1
+        concurrency: 1,
+        taskStealing: true,
+        tasksStealingOnBackPressure: true
       },
       ...tasksQueueOptions
     }
   }
 
+  private setTasksQueueSize (size: number): void {
+    for (const workerNode of this.workerNodes) {
+      workerNode.tasksQueueBackPressureSize = size
+    }
+  }
+
+  private setTaskStealing (): void {
+    for (const [workerNodeKey] of this.workerNodes.entries()) {
+      this.workerNodes[workerNodeKey].addEventListener(
+        'emptyqueue',
+        this.handleEmptyQueueEvent
+      )
+    }
+  }
+
+  private unsetTaskStealing (): void {
+    for (const [workerNodeKey] of this.workerNodes.entries()) {
+      this.workerNodes[workerNodeKey].removeEventListener(
+        'emptyqueue',
+        this.handleEmptyQueueEvent
+      )
+    }
+  }
+
+  private setTasksStealingOnBackPressure (): void {
+    for (const [workerNodeKey] of this.workerNodes.entries()) {
+      this.workerNodes[workerNodeKey].addEventListener(
+        'backpressure',
+        this.handleBackPressureEvent
+      )
+    }
+  }
+
+  private unsetTasksStealingOnBackPressure (): void {
+    for (const [workerNodeKey] of this.workerNodes.entries()) {
+      this.workerNodes[workerNodeKey].removeEventListener(
+        'backpressure',
+        this.handleBackPressureEvent
+      )
+    }
+  }
+
   /**
    * Whether the pool is full or not.
    *
@@ -734,63 +698,93 @@ export abstract class AbstractPool<
     workerNodeKey: number,
     message: MessageValue<Data>
   ): Promise<boolean> {
-    const workerId = this.getWorkerInfo(workerNodeKey).id as number
     return await new Promise<boolean>((resolve, reject) => {
-      this.registerWorkerMessageListener(workerNodeKey, message => {
+      const taskFunctionOperationListener = (
+        message: MessageValue<Response>
+      ): void => {
+        this.checkMessageWorkerId(message)
+        const workerId = this.getWorkerInfo(workerNodeKey).id as number
         if (
-          message.workerId === workerId &&
-          message.taskFunctionOperationStatus === true
-        ) {
-          resolve(true)
-        } else if (
-          message.workerId === workerId &&
-          message.taskFunctionOperationStatus === false
+          message.taskFunctionOperationStatus != null &&
+          message.workerId === workerId
         ) {
-          reject(
-            new Error(
-              `Task function operation ${
-                message.taskFunctionOperation as string
-              } failed on worker ${message.workerId}`
+          if (message.taskFunctionOperationStatus) {
+            resolve(true)
+          } else if (!message.taskFunctionOperationStatus) {
+            reject(
+              new Error(
+                `Task function operation '${
+                  message.taskFunctionOperation as string
+                }' failed on worker ${message.workerId} with error: '${
+                  message.workerError?.message as string
+                }'`
+              )
             )
+          }
+          this.deregisterWorkerMessageListener(
+            this.getWorkerNodeKeyByWorkerId(message.workerId),
+            taskFunctionOperationListener
           )
         }
-      })
+      }
+      this.registerWorkerMessageListener(
+        workerNodeKey,
+        taskFunctionOperationListener
+      )
       this.sendToWorker(workerNodeKey, message)
     })
   }
 
   private async sendTaskFunctionOperationToWorkers (
-    message: Omit<MessageValue<Data>, 'workerId'>
+    message: MessageValue<Data>
   ): Promise<boolean> {
     return await new Promise<boolean>((resolve, reject) => {
-      const responsesReceived = new Array<MessageValue<Data | Response>>()
-      for (const [workerNodeKey] of this.workerNodes.entries()) {
-        this.registerWorkerMessageListener(workerNodeKey, message => {
-          if (message.taskFunctionOperationStatus != null) {
-            responsesReceived.push(message)
+      const responsesReceived = new Array<MessageValue<Response>>()
+      const taskFunctionOperationsListener = (
+        message: MessageValue<Response>
+      ): void => {
+        this.checkMessageWorkerId(message)
+        if (message.taskFunctionOperationStatus != null) {
+          responsesReceived.push(message)
+          if (responsesReceived.length === this.workerNodes.length) {
             if (
-              responsesReceived.length === this.workerNodes.length &&
               responsesReceived.every(
                 message => message.taskFunctionOperationStatus === true
               )
             ) {
               resolve(true)
             } else if (
-              responsesReceived.length === this.workerNodes.length &&
               responsesReceived.some(
                 message => message.taskFunctionOperationStatus === false
               )
             ) {
+              const errorResponse = responsesReceived.find(
+                response => response.taskFunctionOperationStatus === false
+              )
               reject(
                 new Error(
-                  `Task function operation ${
+                  `Task function operation '${
                     message.taskFunctionOperation as string
-                  } failed on worker ${message.workerId as number}`
+                  }' failed on worker ${
+                    errorResponse?.workerId as number
+                  } with error: '${
+                    errorResponse?.workerError?.message as string
+                  }'`
                 )
               )
             }
+            this.deregisterWorkerMessageListener(
+              this.getWorkerNodeKeyByWorkerId(message.workerId),
+              taskFunctionOperationsListener
+            )
           }
-        })
+        }
+      }
+      for (const [workerNodeKey] of this.workerNodes.entries()) {
+        this.registerWorkerMessageListener(
+          workerNodeKey,
+          taskFunctionOperationsListener
+        )
         this.sendToWorker(workerNodeKey, message)
       }
     })
@@ -812,23 +806,40 @@ export abstract class AbstractPool<
   /** @inheritDoc */
   public async addTaskFunction (
     name: string,
-    taskFunction: TaskFunction<Data, Response>
+    fn: TaskFunction<Data, Response>
   ): Promise<boolean> {
-    this.taskFunctions.set(name, taskFunction)
-    return await this.sendTaskFunctionOperationToWorkers({
+    if (typeof name !== 'string') {
+      throw new TypeError('name argument must be a string')
+    }
+    if (typeof name === 'string' && name.trim().length === 0) {
+      throw new TypeError('name argument must not be an empty string')
+    }
+    if (typeof fn !== 'function') {
+      throw new TypeError('fn argument must be a function')
+    }
+    const opResult = await this.sendTaskFunctionOperationToWorkers({
       taskFunctionOperation: 'add',
       taskFunctionName: name,
-      taskFunction: taskFunction.toString()
+      taskFunction: fn.toString()
     })
+    this.taskFunctions.set(name, fn)
+    return opResult
   }
 
   /** @inheritDoc */
   public async removeTaskFunction (name: string): Promise<boolean> {
-    this.taskFunctions.delete(name)
-    return await this.sendTaskFunctionOperationToWorkers({
+    if (!this.taskFunctions.has(name)) {
+      throw new Error(
+        'Cannot remove a task function not handled on the pool side'
+      )
+    }
+    const opResult = await this.sendTaskFunctionOperationToWorkers({
       taskFunctionOperation: 'remove',
       taskFunctionName: name
     })
+    this.deleteTaskFunctionWorkerUsages(name)
+    this.taskFunctions.delete(name)
+    return opResult
   }
 
   /** @inheritDoc */
@@ -852,6 +863,12 @@ export abstract class AbstractPool<
     })
   }
 
+  private deleteTaskFunctionWorkerUsages (name: string): void {
+    for (const workerNode of this.workerNodes) {
+      workerNode.deleteTaskFunctionWorkerUsage(name)
+    }
+  }
+
   private shallExecuteTask (workerNodeKey: number): boolean {
     return (
       this.tasksQueueSize(workerNodeKey) === 0 &&
@@ -868,7 +885,7 @@ export abstract class AbstractPool<
   ): Promise<Response> {
     return await new Promise<Response>((resolve, reject) => {
       if (!this.started) {
-        reject(new Error('Cannot execute a task on destroyed pool'))
+        reject(new Error('Cannot execute a task on not started pool'))
         return
       }
       if (name != null && typeof name !== 'string') {
@@ -914,6 +931,22 @@ export abstract class AbstractPool<
     })
   }
 
+  /** @inheritdoc */
+  public start (): void {
+    this.starting = true
+    while (
+      this.workerNodes.reduce(
+        (accumulator, workerNode) =>
+          !workerNode.info.dynamic ? accumulator + 1 : accumulator,
+        0
+      ) < this.numberOfWorkers
+    ) {
+      this.createAndSetupWorkerNode()
+    }
+    this.starting = false
+    this.started = true
+  }
+
   /** @inheritDoc */
   public async destroy (): Promise<void> {
     await Promise.all(
@@ -922,6 +955,7 @@ export abstract class AbstractPool<
       })
     )
     this.emitter?.emit(PoolEvents.destroy, this.info)
+    this.emitter?.emitDestroy()
     this.started = false
   }
 
@@ -929,19 +963,21 @@ export abstract class AbstractPool<
     workerNodeKey: number
   ): Promise<void> {
     await new Promise<void>((resolve, reject) => {
-      this.registerWorkerMessageListener(workerNodeKey, message => {
+      const killMessageListener = (message: MessageValue<Response>): void => {
+        this.checkMessageWorkerId(message)
         if (message.kill === 'success') {
           resolve()
         } else if (message.kill === 'failure') {
           reject(
             new Error(
-              `Worker ${
+              `Kill message handling failed on worker ${
                 message.workerId as number
-              } kill message handling failed`
+              }`
             )
           )
         }
-      })
+      }
+      this.registerWorkerMessageListener(workerNodeKey, killMessageListener)
       this.sendToWorker(workerNodeKey, { kill: true })
     })
   }
@@ -1188,12 +1224,12 @@ export abstract class AbstractPool<
       const workerNodeKey = this.getWorkerNodeKeyByWorker(worker)
       const workerInfo = this.getWorkerInfo(workerNodeKey)
       workerInfo.ready = false
-      this.workerNodes[workerNodeKey].closeChannel()
       this.emitter?.emit(PoolEvents.error, error)
+      this.workerNodes[workerNodeKey].closeChannel()
       if (
-        this.opts.restartWorkerOnError === true &&
         this.started &&
-        !this.starting
+        !this.starting &&
+        this.opts.restartWorkerOnError === true
       ) {
         if (workerInfo.dynamic) {
           this.createAndSetupDynamicWorkerNode()
@@ -1201,7 +1237,7 @@ export abstract class AbstractPool<
           this.createAndSetupWorkerNode()
         }
       }
-      if (this.opts.enableTasksQueue === true) {
+      if (this.started && this.opts.enableTasksQueue === true) {
         this.redistributeQueuedTasks(workerNodeKey)
       }
     })
@@ -1225,6 +1261,7 @@ export abstract class AbstractPool<
   protected createAndSetupDynamicWorkerNode (): number {
     const workerNodeKey = this.createAndSetupWorkerNode()
     this.registerWorkerMessageListener(workerNodeKey, message => {
+      this.checkMessageWorkerId(message)
       const localWorkerNodeKey = this.getWorkerNodeKeyByWorkerId(
         message.workerId
       )
@@ -1283,6 +1320,32 @@ export abstract class AbstractPool<
     listener: (message: MessageValue<Message>) => void
   ): void
 
+  /**
+   * Registers once a listener callback on the worker given its worker node key.
+   *
+   * @param workerNodeKey - The worker node key.
+   * @param listener - The message listener callback.
+   */
+  protected abstract registerOnceWorkerMessageListener<
+    Message extends Data | Response
+  >(
+    workerNodeKey: number,
+    listener: (message: MessageValue<Message>) => void
+  ): void
+
+  /**
+   * Deregisters a listener callback on the worker given its worker node key.
+   *
+   * @param workerNodeKey - The worker node key.
+   * @param listener - The message listener callback.
+   */
+  protected abstract deregisterWorkerMessageListener<
+    Message extends Data | Response
+  >(
+    workerNodeKey: number,
+    listener: (message: MessageValue<Message>) => void
+  ): void
+
   /**
    * Method hooked up after a worker node has been newly created.
    * Can be overridden.
@@ -1291,16 +1354,27 @@ export abstract class AbstractPool<
    */
   protected afterWorkerNodeSetup (workerNodeKey: number): void {
     // Listen to worker messages.
-    this.registerWorkerMessageListener(workerNodeKey, this.workerListener())
+    this.registerWorkerMessageListener(
+      workerNodeKey,
+      this.workerMessageListener.bind(this)
+    )
     // Send the startup message to worker.
     this.sendStartupMessageToWorker(workerNodeKey)
     // Send the statistics message to worker.
     this.sendStatisticsMessageToWorker(workerNodeKey)
     if (this.opts.enableTasksQueue === true) {
-      this.workerNodes[workerNodeKey].onEmptyQueue =
-        this.taskStealingOnEmptyQueue.bind(this)
-      this.workerNodes[workerNodeKey].onBackPressure =
-        this.tasksStealingOnBackPressure.bind(this)
+      if (this.opts.tasksQueueOptions?.taskStealing === true) {
+        this.workerNodes[workerNodeKey].addEventListener(
+          'emptyqueue',
+          this.handleEmptyQueueEvent
+        )
+      }
+      if (this.opts.tasksQueueOptions?.tasksStealingOnBackPressure === true) {
+        this.workerNodes[workerNodeKey].addEventListener(
+          'backpressure',
+          this.handleBackPressureEvent
+        )
+      }
     }
   }
 
@@ -1368,8 +1442,12 @@ export abstract class AbstractPool<
     }
   }
 
-  private taskStealingOnEmptyQueue (workerId: number): void {
-    const destinationWorkerNodeKey = this.getWorkerNodeKeyByWorkerId(workerId)
+  private readonly handleEmptyQueueEvent = (
+    event: CustomEvent<WorkerNodeEventDetail>
+  ): void => {
+    const destinationWorkerNodeKey = this.getWorkerNodeKeyByWorkerId(
+      event.detail.workerId
+    )
     const workerNodes = this.workerNodes
       .slice()
       .sort(
@@ -1379,7 +1457,7 @@ export abstract class AbstractPool<
     const sourceWorkerNode = workerNodes.find(
       workerNode =>
         workerNode.info.ready &&
-        workerNode.info.id !== workerId &&
+        workerNode.info.id !== event.detail.workerId &&
         workerNode.usage.tasks.queued > 0
     )
     if (sourceWorkerNode != null) {
@@ -1396,13 +1474,15 @@ export abstract class AbstractPool<
     }
   }
 
-  private tasksStealingOnBackPressure (workerId: number): void {
+  private readonly handleBackPressureEvent = (
+    event: CustomEvent<WorkerNodeEventDetail>
+  ): void => {
     const sizeOffset = 1
     if ((this.opts.tasksQueueOptions?.size as number) <= sizeOffset) {
       return
     }
     const sourceWorkerNode =
-      this.workerNodes[this.getWorkerNodeKeyByWorkerId(workerId)]
+      this.workerNodes[this.getWorkerNodeKeyByWorkerId(event.detail.workerId)]
     const workerNodes = this.workerNodes
       .slice()
       .sort(
@@ -1413,7 +1493,7 @@ export abstract class AbstractPool<
       if (
         sourceWorkerNode.usage.tasks.queued > 0 &&
         workerNode.info.ready &&
-        workerNode.info.id !== workerId &&
+        workerNode.info.id !== event.detail.workerId &&
         workerNode.usage.tasks.queued <
           (this.opts.tasksQueueOptions?.size as number) - sizeOffset
       ) {
@@ -1432,25 +1512,21 @@ export abstract class AbstractPool<
   }
 
   /**
-   * This method is the listener registered for each worker message.
-   *
-   * @returns The listener function to execute when a message is received from a worker.
+   * This method is the message listener registered on each worker.
    */
-  protected workerListener (): (message: MessageValue<Response>) => void {
-    return message => {
-      this.checkMessageWorkerId(message)
-      if (message.ready != null && message.taskFunctionNames != null) {
-        // Worker ready response received from worker
-        this.handleWorkerReadyResponse(message)
-      } else if (message.taskId != null) {
-        // Task execution response received from worker
-        this.handleTaskExecutionResponse(message)
-      } else if (message.taskFunctionNames != null) {
-        // Task function names message received from worker
-        this.getWorkerInfo(
-          this.getWorkerNodeKeyByWorkerId(message.workerId)
-        ).taskFunctionNames = message.taskFunctionNames
-      }
+  protected workerMessageListener (message: MessageValue<Response>): void {
+    this.checkMessageWorkerId(message)
+    if (message.ready != null && message.taskFunctionNames != null) {
+      // Worker ready response received from worker
+      this.handleWorkerReadyResponse(message)
+    } else if (message.taskId != null) {
+      // Task execution response received from worker
+      this.handleTaskExecutionResponse(message)
+    } else if (message.taskFunctionNames != null) {
+      // Task function names message received from worker
+      this.getWorkerInfo(
+        this.getWorkerNodeKeyByWorkerId(message.workerId)
+      ).taskFunctionNames = message.taskFunctionNames
     }
   }
 
@@ -1465,8 +1541,8 @@ export abstract class AbstractPool<
     )
     workerInfo.ready = message.ready as boolean
     workerInfo.taskFunctionNames = message.taskFunctionNames
-    if (this.emitter != null && this.ready) {
-      this.emitter.emit(PoolEvents.ready, this.info)
+    if (this.ready) {
+      this.emitter?.emit(PoolEvents.ready, this.info)
     }
   }