X-Git-Url: https://git.piment-noir.org/?a=blobdiff_plain;f=src%2Fpools%2Fabstract-pool.ts;h=11cc9cc15ef419346827e5f627150f04e73ba158;hb=55d7d6002049be09a06b08da26febe2e8bfa494b;hp=a0fc76c371584d3e69855fe732d720db482cc0bf;hpb=8ea697554e82d9f2854acee9fddb8d2fe2d8f9c4;p=poolifier.git

diff --git a/src/pools/abstract-pool.ts b/src/pools/abstract-pool.ts
index a0fc76c3..11cc9cc1 100644
--- a/src/pools/abstract-pool.ts
+++ b/src/pools/abstract-pool.ts
@@ -2,6 +2,7 @@ import { randomUUID } from 'node:crypto'
 import { performance } from 'node:perf_hooks'
 import type { TransferListItem } from 'node:worker_threads'
 import { EventEmitterAsyncResource } from 'node:events'
+import { AsyncResource } from 'node:async_hooks'
 import type {
   MessageValue,
   PromiseResponseWrapper,
@@ -12,12 +13,14 @@ import {
   DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS,
   EMPTY_FUNCTION,
   average,
+  exponentialDelay,
   isKillBehavior,
   isPlainObject,
   max,
   median,
   min,
-  round
+  round,
+  sleep
 } from '../utils'
 import { KillBehaviors } from '../worker/worker-options'
 import type { TaskFunction } from '../worker/task-functions'
@@ -33,13 +36,13 @@ import {
 import type {
   IWorker,
   IWorkerNode,
+  TaskStatistics,
   WorkerInfo,
   WorkerNodeEventDetail,
   WorkerType,
   WorkerUsage
 } from './worker'
 import {
-  type MeasurementStatisticsRequirements,
   Measurements,
   WorkerChoiceStrategies,
   type WorkerChoiceStrategy,
@@ -52,7 +55,12 @@ import {
   checkFilePath,
   checkValidTasksQueueOptions,
   checkValidWorkerChoiceStrategy,
-  updateMeasurementStatistics
+  getDefaultTasksQueueOptions,
+  updateEluWorkerUsage,
+  updateRunTimeWorkerUsage,
+  updateTaskStatisticsWorkerUsage,
+  updateWaitTimeWorkerUsage,
+  waitWorkerNodeEvents
 } from './utils'
 
 /**
@@ -112,6 +120,14 @@ export abstract class AbstractPool<
    * Whether the pool is starting or not.
    */
   private starting: boolean
+  /**
+   * Whether the pool is destroying or not.
+   */
+  private destroying: boolean
+  /**
+   * Whether the pool ready event has been emitted or not.
+   */
+  private readyEventEmitted: boolean
   /**
    * The start timestamp of the pool.
    */
@@ -161,6 +177,8 @@ export abstract class AbstractPool<
 
     this.started = false
     this.starting = false
+    this.destroying = false
+    this.readyEventEmitted = false
     if (this.opts.startWorkers === true) {
       this.start()
     }
@@ -292,8 +310,8 @@ export abstract class AbstractPool<
         0
       ),
       busyWorkerNodes: this.workerNodes.reduce(
-        (accumulator, workerNode) =>
-          workerNode.usage.tasks.executing > 0 ? accumulator + 1 : accumulator,
+        (accumulator, _workerNode, workerNodeKey) =>
+          this.isWorkerNodeBusy(workerNodeKey) ? accumulator + 1 : accumulator,
         0
       ),
       executedTasks: this.workerNodes.reduce(
@@ -495,28 +513,13 @@ export abstract class AbstractPool<
   private checkMessageWorkerId (message: MessageValue<Data | Response>): void {
     if (message.workerId == null) {
       throw new Error('Worker message received without worker id')
-    } else if (
-      message.workerId != null &&
-      this.getWorkerNodeKeyByWorkerId(message.workerId) === -1
-    ) {
+    } else if (this.getWorkerNodeKeyByWorkerId(message.workerId) === -1) {
       throw new Error(
         `Worker message received from unknown worker '${message.workerId}'`
       )
     }
   }
 
-  /**
-   * Gets the given worker its worker node key.
-   *
-   * @param worker - The worker.
-   * @returns The worker node key if found in the pool worker nodes, `-1` otherwise.
-   */
-  private getWorkerNodeKeyByWorker (worker: Worker): number {
-    return this.workerNodes.findIndex(
-      workerNode => workerNode.worker === worker
-    )
-  }
-
   /**
    * Gets the worker node key given its worker id.
    *
@@ -584,11 +587,13 @@ export abstract class AbstractPool<
         this.buildTasksQueueOptions(tasksQueueOptions)
       this.setTasksQueueSize(this.opts.tasksQueueOptions.size as number)
       if (this.opts.tasksQueueOptions.taskStealing === true) {
+        this.unsetTaskStealing()
         this.setTaskStealing()
       } else {
         this.unsetTaskStealing()
       }
       if (this.opts.tasksQueueOptions.tasksStealingOnBackPressure === true) {
+        this.unsetTasksStealingOnBackPressure()
         this.setTasksStealingOnBackPressure()
       } else {
         this.unsetTasksStealingOnBackPressure()
@@ -602,12 +607,7 @@ export abstract class AbstractPool<
     tasksQueueOptions: TasksQueueOptions
   ): TasksQueueOptions {
     return {
-      ...{
-        size: Math.pow(this.maxSize, 2),
-        concurrency: 1,
-        taskStealing: true,
-        tasksStealingOnBackPressure: true
-      },
+      ...getDefaultTasksQueueOptions(this.maxSize),
       ...tasksQueueOptions
     }
   }
@@ -620,26 +620,26 @@ export abstract class AbstractPool<
 
   private setTaskStealing (): void {
     for (const [workerNodeKey] of this.workerNodes.entries()) {
-      this.workerNodes[workerNodeKey].addEventListener(
-        'emptyqueue',
-        this.handleEmptyQueueEvent
+      this.workerNodes[workerNodeKey].on(
+        'idleWorkerNode',
+        this.handleIdleWorkerNodeEvent
       )
     }
   }
 
   private unsetTaskStealing (): void {
     for (const [workerNodeKey] of this.workerNodes.entries()) {
-      this.workerNodes[workerNodeKey].removeEventListener(
-        'emptyqueue',
-        this.handleEmptyQueueEvent
+      this.workerNodes[workerNodeKey].off(
+        'idleWorkerNode',
+        this.handleIdleWorkerNodeEvent
       )
     }
   }
 
   private setTasksStealingOnBackPressure (): void {
     for (const [workerNodeKey] of this.workerNodes.entries()) {
-      this.workerNodes[workerNodeKey].addEventListener(
-        'backpressure',
+      this.workerNodes[workerNodeKey].on(
+        'backPressure',
         this.handleBackPressureEvent
       )
     }
@@ -647,8 +647,8 @@ export abstract class AbstractPool<
 
   private unsetTasksStealingOnBackPressure (): void {
     for (const [workerNodeKey] of this.workerNodes.entries()) {
-      this.workerNodes[workerNodeKey].removeEventListener(
-        'backpressure',
+      this.workerNodes[workerNodeKey].off(
+        'backPressure',
         this.handleBackPressureEvent
       )
     }
@@ -694,6 +694,16 @@ export abstract class AbstractPool<
     )
   }
 
+  private isWorkerNodeBusy (workerNodeKey: number): boolean {
+    if (this.opts.enableTasksQueue === true) {
+      return (
+        this.workerNodes[workerNodeKey].usage.tasks.executing >=
+        (this.opts.tasksQueueOptions?.concurrency as number)
+      )
+    }
+    return this.workerNodes[workerNodeKey].usage.tasks.executing > 0
+  }
+
   private async sendTaskFunctionOperationToWorker (
     workerNodeKey: number,
     message: MessageValue<Data>
@@ -888,6 +898,10 @@ export abstract class AbstractPool<
         reject(new Error('Cannot execute a task on not started pool'))
         return
       }
+      if (this.destroying) {
+        reject(new Error('Cannot execute a task on destroying pool'))
+        return
+      }
       if (name != null && typeof name !== 'string') {
         reject(new TypeError('name argument must be a string'))
         return
@@ -917,7 +931,13 @@ export abstract class AbstractPool<
       this.promiseResponseMap.set(task.taskId as string, {
         resolve,
         reject,
-        workerNodeKey
+        workerNodeKey,
+        ...(this.emitter != null && {
+          asyncResource: new AsyncResource('poolifier:task', {
+            triggerAsyncId: this.emitter.asyncId,
+            requireManualDestroy: true
+          })
+        })
       })
       if (
         this.opts.enableTasksQueue === false ||
@@ -933,6 +953,15 @@ export abstract class AbstractPool<
 
   /** @inheritdoc */
   public start (): void {
+    if (this.started) {
+      throw new Error('Cannot start an already started pool')
+    }
+    if (this.starting) {
+      throw new Error('Cannot start an already starting pool')
+    }
+    if (this.destroying) {
+      throw new Error('Cannot start a destroying pool')
+    }
     this.starting = true
     while (
       this.workerNodes.reduce(
@@ -949,13 +978,26 @@ export abstract class AbstractPool<
 
   /** @inheritDoc */
   public async destroy (): Promise<void> {
+    if (!this.started) {
+      throw new Error('Cannot destroy an already destroyed pool')
+    }
+    if (this.starting) {
+      throw new Error('Cannot destroy an starting pool')
+    }
+    if (this.destroying) {
+      throw new Error('Cannot destroy an already destroying pool')
+    }
+    this.destroying = true
     await Promise.all(
-      this.workerNodes.map(async (_, workerNodeKey) => {
+      this.workerNodes.map(async (_workerNode, workerNodeKey) => {
         await this.destroyWorkerNode(workerNodeKey)
       })
     )
     this.emitter?.emit(PoolEvents.destroy, this.info)
     this.emitter?.emitDestroy()
+    this.emitter?.removeAllListeners()
+    this.readyEventEmitted = false
+    this.destroying = false
     this.started = false
   }
 
@@ -963,6 +1005,10 @@ export abstract class AbstractPool<
     workerNodeKey: number
   ): Promise<void> {
     await new Promise<void>((resolve, reject) => {
+      if (workerNodeKey < 0 || workerNodeKey >= this.workerNodes.length) {
+        reject(new Error(`Invalid worker node key '${workerNodeKey}'`))
+        return
+      }
       const killMessageListener = (message: MessageValue<Response>): void => {
         this.checkMessageWorkerId(message)
         if (message.kill === 'success') {
@@ -977,6 +1023,7 @@ export abstract class AbstractPool<
           )
         }
       }
+      // FIXME: should be registered only once
       this.registerWorkerMessageListener(workerNodeKey, killMessageListener)
       this.sendToWorker(workerNodeKey, { kill: true })
     })
@@ -987,7 +1034,20 @@ export abstract class AbstractPool<
    *
    * @param workerNodeKey - The worker node key.
    */
-  protected abstract destroyWorkerNode (workerNodeKey: number): Promise<void>
+  protected async destroyWorkerNode (workerNodeKey: number): Promise<void> {
+    this.flagWorkerNodeAsNotReady(workerNodeKey)
+    const flushedTasks = this.flushTasksQueue(workerNodeKey)
+    const workerNode = this.workerNodes[workerNodeKey]
+    await waitWorkerNodeEvents(
+      workerNode,
+      'taskFinished',
+      flushedTasks,
+      this.opts.tasksQueueOptions?.tasksFinishedTimeout ??
+        getDefaultTasksQueueOptions(this.maxSize).tasksFinishedTimeout
+    )
+    await this.sendKillMessageToWorker(workerNodeKey)
+    await workerNode.terminate()
+  }
 
   /**
    * Setup hook to execute code before worker nodes are created in the abstract constructor.
@@ -1018,7 +1078,11 @@ export abstract class AbstractPool<
     if (this.workerNodes[workerNodeKey]?.usage != null) {
       const workerUsage = this.workerNodes[workerNodeKey].usage
       ++workerUsage.tasks.executing
-      this.updateWaitTimeWorkerUsage(workerUsage, task)
+      updateWaitTimeWorkerUsage(
+        this.workerChoiceStrategyContext,
+        workerUsage,
+        task
+      )
     }
     if (
       this.shallUpdateTaskFunctionWorkerUsage(workerNodeKey) &&
@@ -1030,7 +1094,11 @@ export abstract class AbstractPool<
         workerNodeKey
       ].getTaskFunctionWorkerUsage(task.name as string) as WorkerUsage
       ++taskFunctionWorkerUsage.tasks.executing
-      this.updateWaitTimeWorkerUsage(taskFunctionWorkerUsage, task)
+      updateWaitTimeWorkerUsage(
+        this.workerChoiceStrategyContext,
+        taskFunctionWorkerUsage,
+        task
+      )
     }
   }
 
@@ -1045,11 +1113,21 @@ export abstract class AbstractPool<
     workerNodeKey: number,
     message: MessageValue<Response>
   ): void {
+    let needWorkerChoiceStrategyUpdate = false
     if (this.workerNodes[workerNodeKey]?.usage != null) {
       const workerUsage = this.workerNodes[workerNodeKey].usage
-      this.updateTaskStatisticsWorkerUsage(workerUsage, message)
-      this.updateRunTimeWorkerUsage(workerUsage, message)
-      this.updateEluWorkerUsage(workerUsage, message)
+      updateTaskStatisticsWorkerUsage(workerUsage, message)
+      updateRunTimeWorkerUsage(
+        this.workerChoiceStrategyContext,
+        workerUsage,
+        message
+      )
+      updateEluWorkerUsage(
+        this.workerChoiceStrategyContext,
+        workerUsage,
+        message
+      )
+      needWorkerChoiceStrategyUpdate = true
     }
     if (
       this.shallUpdateTaskFunctionWorkerUsage(workerNodeKey) &&
@@ -1062,9 +1140,21 @@ export abstract class AbstractPool<
       ].getTaskFunctionWorkerUsage(
         message.taskPerformance?.name as string
       ) as WorkerUsage
-      this.updateTaskStatisticsWorkerUsage(taskFunctionWorkerUsage, message)
-      this.updateRunTimeWorkerUsage(taskFunctionWorkerUsage, message)
-      this.updateEluWorkerUsage(taskFunctionWorkerUsage, message)
+      updateTaskStatisticsWorkerUsage(taskFunctionWorkerUsage, message)
+      updateRunTimeWorkerUsage(
+        this.workerChoiceStrategyContext,
+        taskFunctionWorkerUsage,
+        message
+      )
+      updateEluWorkerUsage(
+        this.workerChoiceStrategyContext,
+        taskFunctionWorkerUsage,
+        message
+      )
+      needWorkerChoiceStrategyUpdate = true
+    }
+    if (needWorkerChoiceStrategyUpdate) {
+      this.workerChoiceStrategyContext.update(workerNodeKey)
     }
   }
 
@@ -1083,84 +1173,6 @@ export abstract class AbstractPool<
     )
   }
 
-  private updateTaskStatisticsWorkerUsage (
-    workerUsage: WorkerUsage,
-    message: MessageValue<Response>
-  ): void {
-    const workerTaskStatistics = workerUsage.tasks
-    if (
-      workerTaskStatistics.executing != null &&
-      workerTaskStatistics.executing > 0
-    ) {
-      --workerTaskStatistics.executing
-    }
-    if (message.workerError == null) {
-      ++workerTaskStatistics.executed
-    } else {
-      ++workerTaskStatistics.failed
-    }
-  }
-
-  private updateRunTimeWorkerUsage (
-    workerUsage: WorkerUsage,
-    message: MessageValue<Response>
-  ): void {
-    if (message.workerError != null) {
-      return
-    }
-    updateMeasurementStatistics(
-      workerUsage.runTime,
-      this.workerChoiceStrategyContext.getTaskStatisticsRequirements().runTime,
-      message.taskPerformance?.runTime ?? 0
-    )
-  }
-
-  private updateWaitTimeWorkerUsage (
-    workerUsage: WorkerUsage,
-    task: Task<Data>
-  ): void {
-    const timestamp = performance.now()
-    const taskWaitTime = timestamp - (task.timestamp ?? timestamp)
-    updateMeasurementStatistics(
-      workerUsage.waitTime,
-      this.workerChoiceStrategyContext.getTaskStatisticsRequirements().waitTime,
-      taskWaitTime
-    )
-  }
-
-  private updateEluWorkerUsage (
-    workerUsage: WorkerUsage,
-    message: MessageValue<Response>
-  ): void {
-    if (message.workerError != null) {
-      return
-    }
-    const eluTaskStatisticsRequirements: MeasurementStatisticsRequirements =
-      this.workerChoiceStrategyContext.getTaskStatisticsRequirements().elu
-    updateMeasurementStatistics(
-      workerUsage.elu.active,
-      eluTaskStatisticsRequirements,
-      message.taskPerformance?.elu?.active ?? 0
-    )
-    updateMeasurementStatistics(
-      workerUsage.elu.idle,
-      eluTaskStatisticsRequirements,
-      message.taskPerformance?.elu?.idle ?? 0
-    )
-    if (eluTaskStatisticsRequirements.aggregate) {
-      if (message.taskPerformance?.elu != null) {
-        if (workerUsage.elu.utilization != null) {
-          workerUsage.elu.utilization =
-            (workerUsage.elu.utilization +
-              message.taskPerformance.elu.utilization) /
-            2
-        } else {
-          workerUsage.elu.utilization = message.taskPerformance.elu.utilization
-        }
-      }
-    }
-  }
-
   /**
    * Chooses a worker node for the next task.
    *
@@ -1202,54 +1214,56 @@ export abstract class AbstractPool<
     transferList?: TransferListItem[]
   ): void
 
-  /**
-   * Creates a new worker.
-   *
-   * @returns Newly created worker.
-   */
-  protected abstract createWorker (): Worker
-
   /**
    * Creates a new, completely set up worker node.
    *
    * @returns New, completely set up worker node key.
    */
   protected createAndSetupWorkerNode (): number {
-    const worker = this.createWorker()
-
-    worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
-    worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
-    worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
-    worker.on('error', error => {
-      const workerNodeKey = this.getWorkerNodeKeyByWorker(worker)
-      const workerInfo = this.getWorkerInfo(workerNodeKey)
-      workerInfo.ready = false
+    const workerNode = this.createWorkerNode()
+    workerNode.registerWorkerEventHandler(
+      'online',
+      this.opts.onlineHandler ?? EMPTY_FUNCTION
+    )
+    workerNode.registerWorkerEventHandler(
+      'message',
+      this.opts.messageHandler ?? EMPTY_FUNCTION
+    )
+    workerNode.registerWorkerEventHandler(
+      'error',
+      this.opts.errorHandler ?? EMPTY_FUNCTION
+    )
+    workerNode.registerWorkerEventHandler('error', (error: Error) => {
+      workerNode.info.ready = false
       this.emitter?.emit(PoolEvents.error, error)
-      this.workerNodes[workerNodeKey].closeChannel()
       if (
         this.started &&
         !this.starting &&
+        !this.destroying &&
         this.opts.restartWorkerOnError === true
       ) {
-        if (workerInfo.dynamic) {
+        if (workerNode.info.dynamic) {
           this.createAndSetupDynamicWorkerNode()
         } else {
           this.createAndSetupWorkerNode()
         }
       }
       if (this.started && this.opts.enableTasksQueue === true) {
-        this.redistributeQueuedTasks(workerNodeKey)
+        this.redistributeQueuedTasks(this.workerNodes.indexOf(workerNode))
       }
+      workerNode?.terminate().catch(error => {
+        this.emitter?.emit(PoolEvents.error, error)
+      })
     })
-    worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
-    worker.once('exit', () => {
-      this.removeWorkerNode(worker)
+    workerNode.registerWorkerEventHandler(
+      'exit',
+      this.opts.exitHandler ?? EMPTY_FUNCTION
+    )
+    workerNode.registerOnceWorkerEventHandler('exit', () => {
+      this.removeWorkerNode(workerNode)
     })
-
-    const workerNodeKey = this.addWorkerNode(worker)
-
+    const workerNodeKey = this.addWorkerNode(workerNode)
     this.afterWorkerNodeSetup(workerNodeKey)
-
     return workerNodeKey
   }
 
@@ -1276,6 +1290,8 @@ export abstract class AbstractPool<
               workerUsage.tasks.executing === 0 &&
               this.tasksQueueSize(localWorkerNodeKey) === 0)))
       ) {
+        // Flag the worker node as not ready immediately
+        this.flagWorkerNodeAsNotReady(localWorkerNodeKey)
         this.destroyWorkerNode(localWorkerNodeKey).catch(error => {
           this.emitter?.emit(PoolEvents.error, error)
         })
@@ -1356,7 +1372,7 @@ export abstract class AbstractPool<
     // Listen to worker messages.
     this.registerWorkerMessageListener(
       workerNodeKey,
-      this.workerMessageListener.bind(this)
+      this.workerMessageListener
     )
     // Send the startup message to worker.
     this.sendStartupMessageToWorker(workerNodeKey)
@@ -1364,14 +1380,14 @@ export abstract class AbstractPool<
     this.sendStatisticsMessageToWorker(workerNodeKey)
     if (this.opts.enableTasksQueue === true) {
       if (this.opts.tasksQueueOptions?.taskStealing === true) {
-        this.workerNodes[workerNodeKey].addEventListener(
-          'emptyqueue',
-          this.handleEmptyQueueEvent
+        this.workerNodes[workerNodeKey].on(
+          'idleWorkerNode',
+          this.handleIdleWorkerNodeEvent
         )
       }
       if (this.opts.tasksQueueOptions?.tasksStealingOnBackPressure === true) {
-        this.workerNodes[workerNodeKey].addEventListener(
-          'backpressure',
+        this.workerNodes[workerNodeKey].on(
+          'backPressure',
           this.handleBackPressureEvent
         )
       }
@@ -1402,7 +1418,21 @@ export abstract class AbstractPool<
     })
   }
 
+  private handleTask (workerNodeKey: number, task: Task<Data>): void {
+    if (this.shallExecuteTask(workerNodeKey)) {
+      this.executeTask(workerNodeKey, task)
+    } else {
+      this.enqueueTask(workerNodeKey, task)
+    }
+  }
+
   private redistributeQueuedTasks (workerNodeKey: number): void {
+    if (workerNodeKey === -1) {
+      return
+    }
+    if (this.workerNodes.length <= 1) {
+      return
+    }
     while (this.tasksQueueSize(workerNodeKey) > 0) {
       const destinationWorkerNodeKey = this.workerNodes.reduce(
         (minWorkerNodeKey, workerNode, workerNodeKey, workerNodes) => {
@@ -1414,12 +1444,10 @@ export abstract class AbstractPool<
         },
         0
       )
-      const task = this.dequeueTask(workerNodeKey) as Task<Data>
-      if (this.shallExecuteTask(destinationWorkerNodeKey)) {
-        this.executeTask(destinationWorkerNodeKey, task)
-      } else {
-        this.enqueueTask(destinationWorkerNodeKey, task)
-      }
+      this.handleTask(
+        destinationWorkerNodeKey,
+        this.dequeueTask(workerNodeKey) as Task<Data>
+      )
     }
   }
 
@@ -1442,12 +1470,123 @@ export abstract class AbstractPool<
     }
   }
 
-  private readonly handleEmptyQueueEvent = (
-    event: CustomEvent<WorkerNodeEventDetail>
+  private updateTaskSequentiallyStolenStatisticsWorkerUsage (
+    workerNodeKey: number
+  ): void {
+    const workerNode = this.workerNodes[workerNodeKey]
+    if (workerNode?.usage != null) {
+      ++workerNode.usage.tasks.sequentiallyStolen
+    }
+  }
+
+  private updateTaskSequentiallyStolenStatisticsTaskFunctionWorkerUsage (
+    workerNodeKey: number,
+    taskName: string
+  ): void {
+    const workerNode = this.workerNodes[workerNodeKey]
+    if (
+      this.shallUpdateTaskFunctionWorkerUsage(workerNodeKey) &&
+      workerNode.getTaskFunctionWorkerUsage(taskName) != null
+    ) {
+      const taskFunctionWorkerUsage = workerNode.getTaskFunctionWorkerUsage(
+        taskName
+      ) as WorkerUsage
+      ++taskFunctionWorkerUsage.tasks.sequentiallyStolen
+    }
+  }
+
+  private resetTaskSequentiallyStolenStatisticsWorkerUsage (
+    workerNodeKey: number
+  ): void {
+    const workerNode = this.workerNodes[workerNodeKey]
+    if (workerNode?.usage != null) {
+      workerNode.usage.tasks.sequentiallyStolen = 0
+    }
+  }
+
+  private resetTaskSequentiallyStolenStatisticsTaskFunctionWorkerUsage (
+    workerNodeKey: number,
+    taskName: string
+  ): void {
+    const workerNode = this.workerNodes[workerNodeKey]
+    if (
+      this.shallUpdateTaskFunctionWorkerUsage(workerNodeKey) &&
+      workerNode.getTaskFunctionWorkerUsage(taskName) != null
+    ) {
+      const taskFunctionWorkerUsage = workerNode.getTaskFunctionWorkerUsage(
+        taskName
+      ) as WorkerUsage
+      taskFunctionWorkerUsage.tasks.sequentiallyStolen = 0
+    }
+  }
+
+  private readonly handleIdleWorkerNodeEvent = (
+    eventDetail: WorkerNodeEventDetail,
+    previousStolenTask?: Task<Data>
   ): void => {
-    const destinationWorkerNodeKey = this.getWorkerNodeKeyByWorkerId(
-      event.detail.workerId
-    )
+    if (this.workerNodes.length <= 1) {
+      return
+    }
+    const { workerNodeKey } = eventDetail
+    if (workerNodeKey == null) {
+      throw new Error(
+        'WorkerNode event detail workerNodeKey attribute must be defined'
+      )
+    }
+    const workerNodeTasksUsage = this.workerNodes[workerNodeKey].usage.tasks
+    if (
+      previousStolenTask != null &&
+      workerNodeTasksUsage.sequentiallyStolen > 0 &&
+      (workerNodeTasksUsage.executing > 0 ||
+        this.tasksQueueSize(workerNodeKey) > 0)
+    ) {
+      for (const taskName of this.workerNodes[workerNodeKey].info
+        .taskFunctionNames as string[]) {
+        this.resetTaskSequentiallyStolenStatisticsTaskFunctionWorkerUsage(
+          workerNodeKey,
+          taskName
+        )
+      }
+      this.resetTaskSequentiallyStolenStatisticsWorkerUsage(workerNodeKey)
+      return
+    }
+    const stolenTask = this.workerNodeStealTask(workerNodeKey)
+    if (
+      this.shallUpdateTaskFunctionWorkerUsage(workerNodeKey) &&
+      stolenTask != null
+    ) {
+      const taskFunctionTasksWorkerUsage = this.workerNodes[
+        workerNodeKey
+      ].getTaskFunctionWorkerUsage(stolenTask.name as string)
+        ?.tasks as TaskStatistics
+      if (
+        taskFunctionTasksWorkerUsage.sequentiallyStolen === 0 ||
+        (previousStolenTask != null &&
+          previousStolenTask.name === stolenTask.name &&
+          taskFunctionTasksWorkerUsage.sequentiallyStolen > 0)
+      ) {
+        this.updateTaskSequentiallyStolenStatisticsTaskFunctionWorkerUsage(
+          workerNodeKey,
+          stolenTask.name as string
+        )
+      } else {
+        this.resetTaskSequentiallyStolenStatisticsTaskFunctionWorkerUsage(
+          workerNodeKey,
+          stolenTask.name as string
+        )
+      }
+    }
+    sleep(exponentialDelay(workerNodeTasksUsage.sequentiallyStolen))
+      .then(() => {
+        this.handleIdleWorkerNodeEvent(eventDetail, stolenTask)
+        return undefined
+      })
+      .catch(EMPTY_FUNCTION)
+  }
+
+  private readonly workerNodeStealTask = (
+    workerNodeKey: number
+  ): Task<Data> | undefined => {
     const workerNodes = this.workerNodes
       .slice()
       .sort(
@@ -1455,34 +1594,36 @@ export abstract class AbstractPool<
           workerNodeB.usage.tasks.queued - workerNodeA.usage.tasks.queued
       )
     const sourceWorkerNode = workerNodes.find(
-      workerNode =>
-        workerNode.info.ready &&
-        workerNode.info.id !== event.detail.workerId &&
-        workerNode.usage.tasks.queued > 0
+      (sourceWorkerNode, sourceWorkerNodeKey) =>
+        sourceWorkerNode.info.ready &&
+        sourceWorkerNodeKey !== workerNodeKey &&
+        sourceWorkerNode.usage.tasks.queued > 0
     )
     if (sourceWorkerNode != null) {
       const task = sourceWorkerNode.popTask() as Task<Data>
-      if (this.shallExecuteTask(destinationWorkerNodeKey)) {
-        this.executeTask(destinationWorkerNodeKey, task)
-      } else {
-        this.enqueueTask(destinationWorkerNodeKey, task)
-      }
+      this.handleTask(workerNodeKey, task)
+      this.updateTaskSequentiallyStolenStatisticsWorkerUsage(workerNodeKey)
       this.updateTaskStolenStatisticsWorkerUsage(
-        destinationWorkerNodeKey,
+        workerNodeKey,
         task.name as string
       )
+      return task
     }
   }
 
   private readonly handleBackPressureEvent = (
-    event: CustomEvent<WorkerNodeEventDetail>
+    eventDetail: WorkerNodeEventDetail
   ): void => {
+    if (this.workerNodes.length <= 1) {
+      return
+    }
+    const { workerId } = eventDetail
     const sizeOffset = 1
     if ((this.opts.tasksQueueOptions?.size as number) <= sizeOffset) {
       return
     }
     const sourceWorkerNode =
-      this.workerNodes[this.getWorkerNodeKeyByWorkerId(event.detail.workerId)]
+      this.workerNodes[this.getWorkerNodeKeyByWorkerId(workerId)]
     const workerNodes = this.workerNodes
       .slice()
       .sort(
@@ -1493,16 +1634,12 @@ export abstract class AbstractPool<
       if (
         sourceWorkerNode.usage.tasks.queued > 0 &&
         workerNode.info.ready &&
-        workerNode.info.id !== event.detail.workerId &&
+        workerNode.info.id !== workerId &&
         workerNode.usage.tasks.queued <
           (this.opts.tasksQueueOptions?.size as number) - sizeOffset
       ) {
         const task = sourceWorkerNode.popTask() as Task<Data>
-        if (this.shallExecuteTask(workerNodeKey)) {
-          this.executeTask(workerNodeKey, task)
-        } else {
-          this.enqueueTask(workerNodeKey, task)
-        }
+        this.handleTask(workerNodeKey, task)
         this.updateTaskStolenStatisticsWorkerUsage(
           workerNodeKey,
           task.name as string
@@ -1514,62 +1651,87 @@ export abstract class AbstractPool<
   /**
    * This method is the message listener registered on each worker.
    */
-  protected workerMessageListener (message: MessageValue<Response>): void {
+  protected readonly workerMessageListener = (
+    message: MessageValue<Response>
+  ): void => {
     this.checkMessageWorkerId(message)
-    if (message.ready != null && message.taskFunctionNames != null) {
+    const { workerId, ready, taskId, taskFunctionNames } = message
+    if (ready != null && taskFunctionNames != null) {
       // Worker ready response received from worker
       this.handleWorkerReadyResponse(message)
-    } else if (message.taskId != null) {
+    } else if (taskId != null) {
       // Task execution response received from worker
       this.handleTaskExecutionResponse(message)
-    } else if (message.taskFunctionNames != null) {
+    } else if (taskFunctionNames != null) {
       // Task function names message received from worker
       this.getWorkerInfo(
-        this.getWorkerNodeKeyByWorkerId(message.workerId)
-      ).taskFunctionNames = message.taskFunctionNames
+        this.getWorkerNodeKeyByWorkerId(workerId)
+      ).taskFunctionNames = taskFunctionNames
     }
   }
 
   private handleWorkerReadyResponse (message: MessageValue<Response>): void {
-    if (message.ready === false) {
-      throw new Error(
-        `Worker ${message.workerId as number} failed to initialize`
-      )
+    const { workerId, ready, taskFunctionNames } = message
+    if (ready === false) {
+      throw new Error(`Worker ${workerId as number} failed to initialize`)
     }
     const workerInfo = this.getWorkerInfo(
-      this.getWorkerNodeKeyByWorkerId(message.workerId)
+      this.getWorkerNodeKeyByWorkerId(workerId)
     )
-    workerInfo.ready = message.ready as boolean
-    workerInfo.taskFunctionNames = message.taskFunctionNames
-    if (this.ready) {
+    workerInfo.ready = ready as boolean
+    workerInfo.taskFunctionNames = taskFunctionNames
+    if (!this.readyEventEmitted && this.ready) {
+      this.readyEventEmitted = true
       this.emitter?.emit(PoolEvents.ready, this.info)
     }
   }
 
   private handleTaskExecutionResponse (message: MessageValue<Response>): void {
-    const { taskId, workerError, data } = message
+    const { workerId, taskId, workerError, data } = message
     const promiseResponse = this.promiseResponseMap.get(taskId as string)
     if (promiseResponse != null) {
+      const { resolve, reject, workerNodeKey, asyncResource } = promiseResponse
+      const workerNode = this.workerNodes[workerNodeKey]
       if (workerError != null) {
         this.emitter?.emit(PoolEvents.taskError, workerError)
-        promiseResponse.reject(workerError.message)
+        asyncResource != null
+          ? asyncResource.runInAsyncScope(
+            reject,
+            this.emitter,
+            workerError.message
+          )
+          : reject(workerError.message)
       } else {
-        promiseResponse.resolve(data as Response)
+        asyncResource != null
+          ? asyncResource.runInAsyncScope(resolve, this.emitter, data)
+          : resolve(data as Response)
       }
-      const workerNodeKey = promiseResponse.workerNodeKey
+      asyncResource?.emitDestroy()
       this.afterTaskExecutionHook(workerNodeKey, message)
-      this.workerChoiceStrategyContext.update(workerNodeKey)
       this.promiseResponseMap.delete(taskId as string)
-      if (
-        this.opts.enableTasksQueue === true &&
-        this.tasksQueueSize(workerNodeKey) > 0 &&
-        this.workerNodes[workerNodeKey].usage.tasks.executing <
-          (this.opts.tasksQueueOptions?.concurrency as number)
-      ) {
-        this.executeTask(
-          workerNodeKey,
-          this.dequeueTask(workerNodeKey) as Task<Data>
-        )
+      workerNode?.emit('taskFinished', taskId)
+      if (this.opts.enableTasksQueue === true && !this.destroying) {
+        const workerNodeTasksUsage = workerNode.usage.tasks
+        if (
+          this.tasksQueueSize(workerNodeKey) > 0 &&
+          workerNodeTasksUsage.executing <
+            (this.opts.tasksQueueOptions?.concurrency as number)
+        ) {
+          this.executeTask(
+            workerNodeKey,
+            this.dequeueTask(workerNodeKey) as Task<Data>
+          )
+        }
+        if (
+          workerNodeTasksUsage.executing === 0 &&
+          this.tasksQueueSize(workerNodeKey) === 0 &&
+          workerNodeTasksUsage.sequentiallyStolen === 0
+        ) {
+          workerNode.emit('idleWorkerNode', {
+            workerId: workerId as number,
+            workerNodeKey
+          })
+        }
       }
     }
   }
@@ -1601,27 +1763,43 @@ export abstract class AbstractPool<
    * @returns The worker information.
    */
   protected getWorkerInfo (workerNodeKey: number): WorkerInfo {
-    return this.workerNodes[workerNodeKey].info
+    return this.workerNodes[workerNodeKey]?.info
   }
 
   /**
-   * Adds the given worker in the pool worker nodes.
+   * Creates a worker node.
    *
-   * @param worker - The worker.
-   * @returns The added worker node key.
-   * @throws {@link https://nodejs.org/api/errors.html#class-error} If the added worker node is not found.
+   * @returns The created worker node.
    */
-  private addWorkerNode (worker: Worker): number {
+  private createWorkerNode (): IWorkerNode<Worker, Data> {
     const workerNode = new WorkerNode<Worker, Data>(
-      worker,
-      this.opts.tasksQueueOptions?.size ?? Math.pow(this.maxSize, 2)
+      this.worker,
+      this.filePath,
+      {
+        env: this.opts.env,
+        workerOptions: this.opts.workerOptions,
+        tasksQueueBackPressureSize:
+          this.opts.tasksQueueOptions?.size ??
+          getDefaultTasksQueueOptions(this.maxSize).size
+      }
     )
     // Flag the worker node as ready at pool startup.
     if (this.starting) {
       workerNode.info.ready = true
     }
+    return workerNode
+  }
+
+  /**
+   * Adds the given worker node in the pool worker nodes.
+   *
+   * @param workerNode - The worker node.
+   * @returns The added worker node key.
+   * @throws {@link https://nodejs.org/api/errors.html#class-error} If the added worker node is not found.
+   */
+  private addWorkerNode (workerNode: IWorkerNode<Worker, Data>): number {
     this.workerNodes.push(workerNode)
-    const workerNodeKey = this.getWorkerNodeKeyByWorker(worker)
+    const workerNodeKey = this.workerNodes.indexOf(workerNode)
     if (workerNodeKey === -1) {
       throw new Error('Worker added not found in worker nodes')
     }
@@ -1629,18 +1807,22 @@ export abstract class AbstractPool<
   }
 
   /**
-   * Removes the given worker from the pool worker nodes.
+   * Removes the worker node from the pool worker nodes.
    *
-   * @param worker - The worker.
+   * @param workerNode - The worker node.
    */
-  private removeWorkerNode (worker: Worker): void {
-    const workerNodeKey = this.getWorkerNodeKeyByWorker(worker)
+  private removeWorkerNode (workerNode: IWorkerNode<Worker, Data>): void {
+    const workerNodeKey = this.workerNodes.indexOf(workerNode)
     if (workerNodeKey !== -1) {
       this.workerNodes.splice(workerNodeKey, 1)
       this.workerChoiceStrategyContext.remove(workerNodeKey)
     }
   }
 
+  protected flagWorkerNodeAsNotReady (workerNodeKey: number): void {
+    this.getWorkerInfo(workerNodeKey).ready = false
+  }
+
   /** @inheritDoc */
   public hasWorkerNodeBackPressure (workerNodeKey: number): boolean {
     return (
@@ -1684,14 +1866,17 @@ export abstract class AbstractPool<
     return this.workerNodes[workerNodeKey].tasksQueueSize()
   }
 
-  protected flushTasksQueue (workerNodeKey: number): void {
+  protected flushTasksQueue (workerNodeKey: number): number {
+    let flushedTasks = 0
     while (this.tasksQueueSize(workerNodeKey) > 0) {
       this.executeTask(
         workerNodeKey,
         this.dequeueTask(workerNodeKey) as Task<Data>
       )
+      ++flushedTasks
     }
     this.workerNodes[workerNodeKey].clearTasksQueue()
+    return flushedTasks
   }
 
   private flushTasksQueues (): void {