X-Git-Url: https://git.piment-noir.org/?a=blobdiff_plain;f=src%2Fpools%2Fabstract-pool.ts;h=eb4c415b4a21be72446bb2da22db83ea9891acb7;hb=d6ca14169b6d2e9ad12d438a7acca797ae683e7e;hp=1aa1a13413f807019352907d2dac7a635ab665d1;hpb=3882157ecadc80e686b319068bd73a9cc218e10c;p=poolifier.git

diff --git a/src/pools/abstract-pool.ts b/src/pools/abstract-pool.ts
index 1aa1a134..eb4c415b 100644
--- a/src/pools/abstract-pool.ts
+++ b/src/pools/abstract-pool.ts
@@ -11,9 +11,12 @@ import {
   DEFAULT_TASK_NAME,
   DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS,
   EMPTY_FUNCTION,
+  average,
   isKillBehavior,
   isPlainObject,
+  max,
   median,
+  min,
   round,
   updateMeasurementStatistics
 } from '../utils'
@@ -65,8 +68,7 @@ export abstract class AbstractPool<
   public readonly emitter?: PoolEmitter
 
   /**
-   * The task execution response promise map.
-   *
+   * The task execution response promise map:
    * - `key`: The message id of each submitted task.
    * - `value`: An object that contains the worker, the execution response promise resolve and reject callbacks.
    *
@@ -89,10 +91,14 @@ export abstract class AbstractPool<
    */
   protected readonly max?: number
 
+  /**
+   * Whether the pool is started or not.
+   */
+  private started: boolean
   /**
    * Whether the pool is starting or not.
    */
-  private readonly starting: boolean
+  private starting: boolean
   /**
    * The start timestamp of the pool.
    */
@@ -138,9 +144,11 @@ export abstract class AbstractPool<
 
     this.setupHook()
 
-    this.starting = true
-    this.startPool()
+    this.started = false
     this.starting = false
+    if (this.opts.startWorkers === true) {
+      this.start()
+    }
 
     this.startTimestamp = performance.now()
   }
@@ -179,7 +187,7 @@ export abstract class AbstractPool<
   protected checkDynamicPoolSize (min: number, max: number): void {
     if (this.type === PoolTypes.dynamic) {
       if (max == null) {
-        throw new Error(
+        throw new TypeError(
           'Cannot instantiate a dynamic pool without specifying the maximum pool size'
         )
       } else if (!Number.isSafeInteger(max)) {
@@ -204,6 +212,7 @@ export abstract class AbstractPool<
 
   private checkPoolOptions (opts: PoolOptions<Worker>): void {
     if (isPlainObject(opts)) {
+      this.opts.startWorkers = opts.startWorkers ?? true
       this.opts.workerChoiceStrategy =
         opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
       this.checkValidWorkerChoiceStrategy(this.opts.workerChoiceStrategy)
@@ -249,19 +258,19 @@ export abstract class AbstractPool<
       )
     }
     if (
-      workerChoiceStrategyOptions.choiceRetries != null &&
-      !Number.isSafeInteger(workerChoiceStrategyOptions.choiceRetries)
+      workerChoiceStrategyOptions.retries != null &&
+      !Number.isSafeInteger(workerChoiceStrategyOptions.retries)
     ) {
       throw new TypeError(
-        'Invalid worker choice strategy options: choice retries must be an integer'
+        'Invalid worker choice strategy options: retries must be an integer'
       )
     }
     if (
-      workerChoiceStrategyOptions.choiceRetries != null &&
-      workerChoiceStrategyOptions.choiceRetries <= 0
+      workerChoiceStrategyOptions.retries != null &&
+      workerChoiceStrategyOptions.retries < 0
     ) {
       throw new RangeError(
-        `Invalid worker choice strategy options: choice retries '${workerChoiceStrategyOptions.choiceRetries}' must be greater than zero`
+        `Invalid worker choice strategy options: retries '${workerChoiceStrategyOptions.retries}' must be greater or equal than zero`
       )
     }
     if (
@@ -292,31 +301,32 @@ export abstract class AbstractPool<
     }
     if (
       tasksQueueOptions?.concurrency != null &&
-      !Number.isSafeInteger(tasksQueueOptions.concurrency)
+      !Number.isSafeInteger(tasksQueueOptions?.concurrency)
     ) {
       throw new TypeError(
-        'Invalid worker tasks concurrency: must be an integer'
+        'Invalid worker node tasks concurrency: must be an integer'
       )
     }
     if (
       tasksQueueOptions?.concurrency != null &&
-      tasksQueueOptions.concurrency <= 0
+      tasksQueueOptions?.concurrency <= 0
     ) {
-      throw new Error(
-        `Invalid worker tasks concurrency: ${tasksQueueOptions.concurrency} is a negative integer or zero`
+      throw new RangeError(
+        `Invalid worker node tasks concurrency: ${tasksQueueOptions?.concurrency} is a negative integer or zero`
       )
     }
-  }
-
-  private startPool (): void {
-    while (
-      this.workerNodes.reduce(
-        (accumulator, workerNode) =>
-          !workerNode.info.dynamic ? accumulator + 1 : accumulator,
-        0
-      ) < this.numberOfWorkers
+    if (
+      tasksQueueOptions?.size != null &&
+      !Number.isSafeInteger(tasksQueueOptions?.size)
     ) {
-      this.createAndSetupWorkerNode()
+      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`
+      )
     }
   }
 
@@ -326,6 +336,7 @@ 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,
@@ -374,6 +385,13 @@ export abstract class AbstractPool<
       ...(this.opts.enableTasksQueue === true && {
         backPressure: this.hasBackPressure()
       }),
+      ...(this.opts.enableTasksQueue === true && {
+        stolenTasks: this.workerNodes.reduce(
+          (accumulator, workerNode) =>
+            accumulator + workerNode.usage.tasks.stolen,
+          0
+        )
+      }),
       failedTasks: this.workerNodes.reduce(
         (accumulator, workerNode) =>
           accumulator + workerNode.usage.tasks.failed,
@@ -383,37 +401,39 @@ export abstract class AbstractPool<
         .runTime.aggregate && {
         runTime: {
           minimum: round(
-            Math.min(
+            min(
               ...this.workerNodes.map(
-                (workerNode) => workerNode.usage.runTime?.minimum ?? Infinity
+                workerNode => workerNode.usage.runTime?.minimum ?? Infinity
               )
             )
           ),
           maximum: round(
-            Math.max(
+            max(
               ...this.workerNodes.map(
-                (workerNode) => workerNode.usage.runTime?.maximum ?? -Infinity
+                workerNode => workerNode.usage.runTime?.maximum ?? -Infinity
               )
             )
           ),
-          average: round(
-            this.workerNodes.reduce(
-              (accumulator, workerNode) =>
-                accumulator + (workerNode.usage.runTime?.aggregate ?? 0),
-              0
-            ) /
-              this.workerNodes.reduce(
-                (accumulator, workerNode) =>
-                  accumulator + (workerNode.usage.tasks?.executed ?? 0),
-                0
+          ...(this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
+            .runTime.average && {
+            average: round(
+              average(
+                this.workerNodes.reduce<number[]>(
+                  (accumulator, workerNode) =>
+                    accumulator.concat(workerNode.usage.runTime.history),
+                  []
+                )
               )
-          ),
+            )
+          }),
           ...(this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
             .runTime.median && {
             median: round(
               median(
-                this.workerNodes.map(
-                  (workerNode) => workerNode.usage.runTime?.median ?? 0
+                this.workerNodes.reduce<number[]>(
+                  (accumulator, workerNode) =>
+                    accumulator.concat(workerNode.usage.runTime.history),
+                  []
                 )
               )
             )
@@ -424,37 +444,39 @@ export abstract class AbstractPool<
         .waitTime.aggregate && {
         waitTime: {
           minimum: round(
-            Math.min(
+            min(
               ...this.workerNodes.map(
-                (workerNode) => workerNode.usage.waitTime?.minimum ?? Infinity
+                workerNode => workerNode.usage.waitTime?.minimum ?? Infinity
               )
             )
           ),
           maximum: round(
-            Math.max(
+            max(
               ...this.workerNodes.map(
-                (workerNode) => workerNode.usage.waitTime?.maximum ?? -Infinity
+                workerNode => workerNode.usage.waitTime?.maximum ?? -Infinity
               )
             )
           ),
-          average: round(
-            this.workerNodes.reduce(
-              (accumulator, workerNode) =>
-                accumulator + (workerNode.usage.waitTime?.aggregate ?? 0),
-              0
-            ) /
-              this.workerNodes.reduce(
-                (accumulator, workerNode) =>
-                  accumulator + (workerNode.usage.tasks?.executed ?? 0),
-                0
+          ...(this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
+            .waitTime.average && {
+            average: round(
+              average(
+                this.workerNodes.reduce<number[]>(
+                  (accumulator, workerNode) =>
+                    accumulator.concat(workerNode.usage.waitTime.history),
+                  []
+                )
               )
-          ),
+            )
+          }),
           ...(this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
             .waitTime.median && {
             median: round(
               median(
-                this.workerNodes.map(
-                  (workerNode) => workerNode.usage.waitTime?.median ?? 0
+                this.workerNodes.reduce<number[]>(
+                  (accumulator, workerNode) =>
+                    accumulator.concat(workerNode.usage.waitTime.history),
+                  []
                 )
               )
             )
@@ -553,7 +575,7 @@ export abstract class AbstractPool<
    */
   private getWorkerNodeKeyByWorker (worker: Worker): number {
     return this.workerNodes.findIndex(
-      (workerNode) => workerNode.worker === worker
+      workerNode => workerNode.worker === worker
     )
   }
 
@@ -565,7 +587,7 @@ export abstract class AbstractPool<
    */
   private getWorkerNodeKeyByWorkerId (workerId: number): number {
     return this.workerNodes.findIndex(
-      (workerNode) => workerNode.info.id === workerId
+      workerNode => workerNode.info.id === workerId
     )
   }
 
@@ -608,6 +630,8 @@ export abstract class AbstractPool<
     tasksQueueOptions?: TasksQueueOptions
   ): void {
     if (this.opts.enableTasksQueue === true && !enable) {
+      this.unsetTaskStealing()
+      this.unsetTasksStealingOnBackPressure()
       this.flushTasksQueues()
     }
     this.opts.enableTasksQueue = enable
@@ -620,16 +644,65 @@ export abstract class AbstractPool<
       this.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 setTaskStealing (): void {
+    for (const [workerNodeKey] of this.workerNodes.entries()) {
+      this.workerNodes[workerNodeKey].onEmptyQueue =
+        this.taskStealingOnEmptyQueue.bind(this)
+    }
+  }
+
+  private unsetTaskStealing (): void {
+    for (const [workerNodeKey] of this.workerNodes.entries()) {
+      delete this.workerNodes[workerNodeKey].onEmptyQueue
+    }
+  }
+
+  private setTasksStealingOnBackPressure (): void {
+    for (const [workerNodeKey] of this.workerNodes.entries()) {
+      this.workerNodes[workerNodeKey].onBackPressure =
+        this.tasksStealingOnBackPressure.bind(this)
+    }
+  }
+
+  private unsetTasksStealingOnBackPressure (): void {
+    for (const [workerNodeKey] of this.workerNodes.entries()) {
+      delete this.workerNodes[workerNodeKey].onBackPressure
+    }
+  }
+
   private buildTasksQueueOptions (
     tasksQueueOptions: TasksQueueOptions
   ): TasksQueueOptions {
     return {
-      concurrency: tasksQueueOptions?.concurrency ?? 1
+      ...{
+        size: Math.pow(this.maxSize, 2),
+        concurrency: 1,
+        taskStealing: true,
+        tasksStealingOnBackPressure: true
+      },
+      ...tasksQueueOptions
     }
   }
 
@@ -658,20 +731,19 @@ export abstract class AbstractPool<
     if (this.opts.enableTasksQueue === true) {
       return (
         this.workerNodes.findIndex(
-          (workerNode) =>
+          workerNode =>
             workerNode.info.ready &&
             workerNode.usage.tasks.executing <
               (this.opts.tasksQueueOptions?.concurrency as number)
         ) === -1
       )
-    } else {
-      return (
-        this.workerNodes.findIndex(
-          (workerNode) =>
-            workerNode.info.ready && workerNode.usage.tasks.executing === 0
-        ) === -1
-      )
     }
+    return (
+      this.workerNodes.findIndex(
+        workerNode =>
+          workerNode.info.ready && workerNode.usage.tasks.executing === 0
+      ) === -1
+    )
   }
 
   /** @inheritDoc */
@@ -687,6 +759,14 @@ export abstract class AbstractPool<
     return []
   }
 
+  private shallExecuteTask (workerNodeKey: number): boolean {
+    return (
+      this.tasksQueueSize(workerNodeKey) === 0 &&
+      this.workerNodes[workerNodeKey].usage.tasks.executing <
+        (this.opts.tasksQueueOptions?.concurrency as number)
+    )
+  }
+
   /** @inheritDoc */
   public async execute (
     data?: Data,
@@ -694,8 +774,13 @@ export abstract class AbstractPool<
     transferList?: TransferListItem[]
   ): Promise<Response> {
     return await new Promise<Response>((resolve, reject) => {
+      if (!this.started) {
+        reject(new Error('Cannot execute a task on not started pool'))
+        return
+      }
       if (name != null && typeof name !== 'string') {
         reject(new TypeError('name argument must be a string'))
+        return
       }
       if (
         name != null &&
@@ -703,29 +788,21 @@ export abstract class AbstractPool<
         name.trim().length === 0
       ) {
         reject(new TypeError('name argument must not be an empty string'))
+        return
       }
       if (transferList != null && !Array.isArray(transferList)) {
         reject(new TypeError('transferList argument must be an array'))
+        return
       }
       const timestamp = performance.now()
       const workerNodeKey = this.chooseWorkerNode()
-      const workerInfo = this.getWorkerInfo(workerNodeKey) as WorkerInfo
-      if (
-        name != null &&
-        Array.isArray(workerInfo.taskFunctions) &&
-        !workerInfo.taskFunctions.includes(name)
-      ) {
-        reject(
-          new Error(`Task function '${name}' is not registered in the pool`)
-        )
-      }
       const task: Task<Data> = {
         name: name ?? DEFAULT_TASK_NAME,
         // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
         data: data ?? ({} as Data),
         transferList,
         timestamp,
-        workerId: workerInfo.id as number,
+        workerId: this.getWorkerInfo(workerNodeKey).id as number,
         taskId: randomUUID()
       }
       this.promiseResponseMap.set(task.taskId as string, {
@@ -736,8 +813,7 @@ export abstract class AbstractPool<
       if (
         this.opts.enableTasksQueue === false ||
         (this.opts.enableTasksQueue === true &&
-          this.workerNodes[workerNodeKey].usage.tasks.executing <
-            (this.opts.tasksQueueOptions?.concurrency as number))
+          this.shallExecuteTask(workerNodeKey))
       ) {
         this.executeTask(workerNodeKey, task)
       } else {
@@ -746,6 +822,22 @@ 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(
@@ -754,6 +846,7 @@ export abstract class AbstractPool<
       })
     )
     this.emitter?.emit(PoolEvents.destroy, this.info)
+    this.started = false
   }
 
   protected async sendKillMessageToWorker (
@@ -761,7 +854,7 @@ export abstract class AbstractPool<
     workerId: number
   ): Promise<void> {
     await new Promise<void>((resolve, reject) => {
-      this.registerWorkerMessageListener(workerNodeKey, (message) => {
+      this.registerWorkerMessageListener(workerNodeKey, message => {
         if (message.kill === 'success') {
           resolve()
         } else if (message.kill === 'failure') {
@@ -786,7 +879,7 @@ export abstract class AbstractPool<
    * @virtual
    */
   protected setupHook (): void {
-    // Intentionally empty
+    /* Intentionally empty */
   }
 
   /**
@@ -850,7 +943,7 @@ export abstract class AbstractPool<
       const taskFunctionWorkerUsage = this.workerNodes[
         workerNodeKey
       ].getTaskFunctionWorkerUsage(
-        message.taskPerformance?.name ?? DEFAULT_TASK_NAME
+        message.taskPerformance?.name as string
       ) as WorkerUsage
       this.updateTaskStatisticsWorkerUsage(taskFunctionWorkerUsage, message)
       this.updateRunTimeWorkerUsage(taskFunctionWorkerUsage, message)
@@ -883,13 +976,6 @@ export abstract class AbstractPool<
       workerTaskStatistics.executing > 0
     ) {
       --workerTaskStatistics.executing
-    } else if (
-      workerTaskStatistics.executing != null &&
-      workerTaskStatistics.executing < 0
-    ) {
-      throw new Error(
-        'Worker usage statistic for tasks executing cannot be negative'
-      )
     }
     if (message.taskError == null) {
       ++workerTaskStatistics.executed
@@ -902,11 +988,13 @@ export abstract class AbstractPool<
     workerUsage: WorkerUsage,
     message: MessageValue<Response>
   ): void {
+    if (message.taskError != null) {
+      return
+    }
     updateMeasurementStatistics(
       workerUsage.runTime,
       this.workerChoiceStrategyContext.getTaskStatisticsRequirements().runTime,
-      message.taskPerformance?.runTime ?? 0,
-      workerUsage.tasks.executed
+      message.taskPerformance?.runTime ?? 0
     )
   }
 
@@ -919,8 +1007,7 @@ export abstract class AbstractPool<
     updateMeasurementStatistics(
       workerUsage.waitTime,
       this.workerChoiceStrategyContext.getTaskStatisticsRequirements().waitTime,
-      taskWaitTime,
-      workerUsage.tasks.executed
+      taskWaitTime
     )
   }
 
@@ -928,19 +1015,20 @@ export abstract class AbstractPool<
     workerUsage: WorkerUsage,
     message: MessageValue<Response>
   ): void {
+    if (message.taskError != null) {
+      return
+    }
     const eluTaskStatisticsRequirements: MeasurementStatisticsRequirements =
       this.workerChoiceStrategyContext.getTaskStatisticsRequirements().elu
     updateMeasurementStatistics(
       workerUsage.elu.active,
       eluTaskStatisticsRequirements,
-      message.taskPerformance?.elu?.active ?? 0,
-      workerUsage.tasks.executed
+      message.taskPerformance?.elu?.active ?? 0
     )
     updateMeasurementStatistics(
       workerUsage.elu.idle,
       eluTaskStatisticsRequirements,
-      message.taskPerformance?.elu?.idle ?? 0,
-      workerUsage.tasks.executed
+      message.taskPerformance?.elu?.idle ?? 0
     )
     if (eluTaskStatisticsRequirements.aggregate) {
       if (message.taskPerformance?.elu != null) {
@@ -1015,13 +1103,17 @@ export abstract class AbstractPool<
     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) => {
+    worker.on('error', error => {
       const workerNodeKey = this.getWorkerNodeKeyByWorker(worker)
-      const workerInfo = this.getWorkerInfo(workerNodeKey) as WorkerInfo
+      const workerInfo = this.getWorkerInfo(workerNodeKey)
       workerInfo.ready = false
       this.workerNodes[workerNodeKey].closeChannel()
       this.emitter?.emit(PoolEvents.error, error)
-      if (this.opts.restartWorkerOnError === true && !this.starting) {
+      if (
+        this.opts.restartWorkerOnError === true &&
+        this.started &&
+        !this.starting
+      ) {
         if (workerInfo.dynamic) {
           this.createAndSetupDynamicWorkerNode()
         } else {
@@ -1051,7 +1143,7 @@ export abstract class AbstractPool<
    */
   protected createAndSetupDynamicWorkerNode (): number {
     const workerNodeKey = this.createAndSetupWorkerNode()
-    this.registerWorkerMessageListener(workerNodeKey, (message) => {
+    this.registerWorkerMessageListener(workerNodeKey, message => {
       const localWorkerNodeKey = this.getWorkerNodeKeyByWorkerId(
         message.workerId
       )
@@ -1066,12 +1158,12 @@ export abstract class AbstractPool<
               workerUsage.tasks.executing === 0 &&
               this.tasksQueueSize(localWorkerNodeKey) === 0)))
       ) {
-        this.destroyWorkerNode(localWorkerNodeKey).catch((error) => {
+        this.destroyWorkerNode(localWorkerNodeKey).catch(error => {
           this.emitter?.emit(PoolEvents.error, error)
         })
       }
     })
-    const workerInfo = this.getWorkerInfo(workerNodeKey) as WorkerInfo
+    const workerInfo = this.getWorkerInfo(workerNodeKey)
     this.sendToWorker(workerNodeKey, {
       checkActive: true,
       workerId: workerInfo.id as number
@@ -1113,6 +1205,16 @@ export abstract class AbstractPool<
     this.sendStartupMessageToWorker(workerNodeKey)
     // Send the statistics message to worker.
     this.sendStatisticsMessageToWorker(workerNodeKey)
+    if (this.opts.enableTasksQueue === true) {
+      if (this.opts.tasksQueueOptions?.taskStealing === true) {
+        this.workerNodes[workerNodeKey].onEmptyQueue =
+          this.taskStealingOnEmptyQueue.bind(this)
+      }
+      if (this.opts.tasksQueueOptions?.tasksStealingOnBackPressure === true) {
+        this.workerNodes[workerNodeKey].onBackPressure =
+          this.tasksStealingOnBackPressure.bind(this)
+      }
+    }
   }
 
   /**
@@ -1136,49 +1238,119 @@ export abstract class AbstractPool<
         elu: this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
           .elu.aggregate
       },
-      workerId: (this.getWorkerInfo(workerNodeKey) as WorkerInfo).id as number
+      workerId: this.getWorkerInfo(workerNodeKey).id as number
     })
   }
 
   private redistributeQueuedTasks (workerNodeKey: number): void {
     while (this.tasksQueueSize(workerNodeKey) > 0) {
-      let targetWorkerNodeKey: number = workerNodeKey
-      let minQueuedTasks = Infinity
-      let executeTask = false
-      for (const [workerNodeId, workerNode] of this.workerNodes.entries()) {
-        const workerInfo = this.getWorkerInfo(workerNodeId) as WorkerInfo
-        if (
-          workerNodeId !== workerNodeKey &&
-          workerInfo.ready &&
-          workerNode.usage.tasks.queued === 0
-        ) {
-          if (
-            this.workerNodes[workerNodeId].usage.tasks.executing <
-            (this.opts.tasksQueueOptions?.concurrency as number)
-          ) {
-            executeTask = true
-          }
-          targetWorkerNodeKey = workerNodeId
-          break
-        }
-        if (
-          workerNodeId !== workerNodeKey &&
-          workerInfo.ready &&
-          workerNode.usage.tasks.queued < minQueuedTasks
-        ) {
-          minQueuedTasks = workerNode.usage.tasks.queued
-          targetWorkerNodeKey = workerNodeId
-        }
+      const destinationWorkerNodeKey = this.workerNodes.reduce(
+        (minWorkerNodeKey, workerNode, workerNodeKey, workerNodes) => {
+          return workerNode.info.ready &&
+            workerNode.usage.tasks.queued <
+              workerNodes[minWorkerNodeKey].usage.tasks.queued
+            ? workerNodeKey
+            : minWorkerNodeKey
+        },
+        0
+      )
+      const destinationWorkerNode = this.workerNodes[destinationWorkerNodeKey]
+      const task = {
+        ...(this.dequeueTask(workerNodeKey) as Task<Data>),
+        workerId: destinationWorkerNode.info.id as number
       }
-      if (executeTask) {
-        this.executeTask(
-          targetWorkerNodeKey,
-          this.dequeueTask(workerNodeKey) as Task<Data>
-        )
+      if (this.shallExecuteTask(destinationWorkerNodeKey)) {
+        this.executeTask(destinationWorkerNodeKey, task)
       } else {
-        this.enqueueTask(
-          targetWorkerNodeKey,
-          this.dequeueTask(workerNodeKey) as Task<Data>
+        this.enqueueTask(destinationWorkerNodeKey, task)
+      }
+    }
+  }
+
+  private updateTaskStolenStatisticsWorkerUsage (
+    workerNodeKey: number,
+    taskName: string
+  ): void {
+    const workerNode = this.workerNodes[workerNodeKey]
+    if (workerNode?.usage != null) {
+      ++workerNode.usage.tasks.stolen
+    }
+    if (
+      this.shallUpdateTaskFunctionWorkerUsage(workerNodeKey) &&
+      workerNode.getTaskFunctionWorkerUsage(taskName) != null
+    ) {
+      const taskFunctionWorkerUsage = workerNode.getTaskFunctionWorkerUsage(
+        taskName
+      ) as WorkerUsage
+      ++taskFunctionWorkerUsage.tasks.stolen
+    }
+  }
+
+  private taskStealingOnEmptyQueue (workerId: number): void {
+    const destinationWorkerNodeKey = this.getWorkerNodeKeyByWorkerId(workerId)
+    const destinationWorkerNode = this.workerNodes[destinationWorkerNodeKey]
+    const workerNodes = this.workerNodes
+      .slice()
+      .sort(
+        (workerNodeA, workerNodeB) =>
+          workerNodeB.usage.tasks.queued - workerNodeA.usage.tasks.queued
+      )
+    const sourceWorkerNode = workerNodes.find(
+      workerNode =>
+        workerNode.info.ready &&
+        workerNode.info.id !== workerId &&
+        workerNode.usage.tasks.queued > 0
+    )
+    if (sourceWorkerNode != null) {
+      const task = {
+        ...(sourceWorkerNode.popTask() as Task<Data>),
+        workerId: destinationWorkerNode.info.id as number
+      }
+      if (this.shallExecuteTask(destinationWorkerNodeKey)) {
+        this.executeTask(destinationWorkerNodeKey, task)
+      } else {
+        this.enqueueTask(destinationWorkerNodeKey, task)
+      }
+      this.updateTaskStolenStatisticsWorkerUsage(
+        destinationWorkerNodeKey,
+        task.name as string
+      )
+    }
+  }
+
+  private tasksStealingOnBackPressure (workerId: number): void {
+    const sizeOffset = 1
+    if ((this.opts.tasksQueueOptions?.size as number) <= sizeOffset) {
+      return
+    }
+    const sourceWorkerNode =
+      this.workerNodes[this.getWorkerNodeKeyByWorkerId(workerId)]
+    const workerNodes = this.workerNodes
+      .slice()
+      .sort(
+        (workerNodeA, workerNodeB) =>
+          workerNodeA.usage.tasks.queued - workerNodeB.usage.tasks.queued
+      )
+    for (const [workerNodeKey, workerNode] of workerNodes.entries()) {
+      if (
+        sourceWorkerNode.usage.tasks.queued > 0 &&
+        workerNode.info.ready &&
+        workerNode.info.id !== workerId &&
+        workerNode.usage.tasks.queued <
+          (this.opts.tasksQueueOptions?.size as number) - sizeOffset
+      ) {
+        const task = {
+          ...(sourceWorkerNode.popTask() as Task<Data>),
+          workerId: workerNode.info.id as number
+        }
+        if (this.shallExecuteTask(workerNodeKey)) {
+          this.executeTask(workerNodeKey, task)
+        } else {
+          this.enqueueTask(workerNodeKey, task)
+        }
+        this.updateTaskStolenStatisticsWorkerUsage(
+          workerNodeKey,
+          task.name as string
         )
       }
     }
@@ -1190,7 +1362,7 @@ export abstract class AbstractPool<
    * @returns The listener function to execute when a message is received from a worker.
    */
   protected workerListener (): (message: MessageValue<Response>) => void {
-    return (message) => {
+    return message => {
       this.checkMessageWorkerId(message)
       if (message.ready != null && message.taskFunctions != null) {
         // Worker ready response received from worker
@@ -1200,10 +1372,8 @@ export abstract class AbstractPool<
         this.handleTaskExecutionResponse(message)
       } else if (message.taskFunctions != null) {
         // Task functions message received from worker
-        (
-          this.getWorkerInfo(
-            this.getWorkerNodeKeyByWorkerId(message.workerId)
-          ) as WorkerInfo
+        this.getWorkerInfo(
+          this.getWorkerNodeKeyByWorkerId(message.workerId)
         ).taskFunctions = message.taskFunctions
       }
     }
@@ -1215,7 +1385,7 @@ export abstract class AbstractPool<
     }
     const workerInfo = this.getWorkerInfo(
       this.getWorkerNodeKeyByWorkerId(message.workerId)
-    ) as WorkerInfo
+    )
     workerInfo.ready = message.ready as boolean
     workerInfo.taskFunctions = message.taskFunctions
     if (this.emitter != null && this.ready) {
@@ -1235,6 +1405,7 @@ export abstract class AbstractPool<
       }
       const workerNodeKey = promiseResponse.workerNodeKey
       this.afterTaskExecutionHook(workerNodeKey, message)
+      this.workerChoiceStrategyContext.update(workerNodeKey)
       this.promiseResponseMap.delete(taskId as string)
       if (
         this.opts.enableTasksQueue === true &&
@@ -1247,7 +1418,6 @@ export abstract class AbstractPool<
           this.dequeueTask(workerNodeKey) as Task<Data>
         )
       }
-      this.workerChoiceStrategyContext.update(workerNodeKey)
     }
   }
 
@@ -1277,8 +1447,8 @@ export abstract class AbstractPool<
    * @param workerNodeKey - The worker node key.
    * @returns The worker information.
    */
-  protected getWorkerInfo (workerNodeKey: number): WorkerInfo | undefined {
-    return this.workerNodes[workerNodeKey]?.info
+  protected getWorkerInfo (workerNodeKey: number): WorkerInfo {
+    return this.workerNodes[workerNodeKey].info
   }
 
   /**
@@ -1291,8 +1461,7 @@ export abstract class AbstractPool<
   private addWorkerNode (worker: Worker): number {
     const workerNode = new WorkerNode<Worker, Data>(
       worker,
-      this.worker,
-      this.maxSize
+      this.opts.tasksQueueOptions?.size ?? Math.pow(this.maxSize, 2)
     )
     // Flag the worker node as ready at pool startup.
     if (this.starting) {
@@ -1301,7 +1470,7 @@ export abstract class AbstractPool<
     this.workerNodes.push(workerNode)
     const workerNodeKey = this.getWorkerNodeKeyByWorker(worker)
     if (workerNodeKey === -1) {
-      throw new Error('Worker node added not found')
+      throw new Error('Worker added not found in worker nodes')
     }
     return workerNodeKey
   }
@@ -1331,7 +1500,7 @@ export abstract class AbstractPool<
     return (
       this.opts.enableTasksQueue === true &&
       this.workerNodes.findIndex(
-        (workerNode) => !workerNode.hasBackPressure()
+        workerNode => !workerNode.hasBackPressure()
       ) === -1
     )
   }