fix: add maximum tasks queue size to worker usage data
[poolifier.git] / src / pools / abstract-pool.ts
index b93915c48e31111b93eb2199ce50fd26dae222b6..6ebb30595d822c525ef98e226bf3239a1d4c475f 100644 (file)
@@ -21,8 +21,9 @@ import {
   type TasksQueueOptions,
   type WorkerType
 } from './pool'
-import type { IWorker, Task, TasksUsage, WorkerNode } from './worker'
+import type { IWorker, Task, WorkerNode, WorkerUsage } from './worker'
 import {
+  Measurements,
   WorkerChoiceStrategies,
   type WorkerChoiceStrategy,
   type WorkerChoiceStrategyOptions
@@ -62,8 +63,6 @@ export abstract class AbstractPool<
 
   /**
    * Worker choice strategy context referencing a worker choice algorithm implementation.
-   *
-   * Default to a round robin algorithm.
    */
   protected workerChoiceStrategyContext: WorkerChoiceStrategyContext<
   Worker,
@@ -195,6 +194,16 @@ export abstract class AbstractPool<
         'Invalid worker choice strategy options: must have a weight for each worker node'
       )
     }
+    if (
+      workerChoiceStrategyOptions.measurement != null &&
+      !Object.values(Measurements).includes(
+        workerChoiceStrategyOptions.measurement
+      )
+    ) {
+      throw new Error(
+        `Invalid worker choice strategy options: invalid measurement '${workerChoiceStrategyOptions.measurement}'`
+      )
+    }
   }
 
   private checkValidTasksQueueOptions (
@@ -203,11 +212,20 @@ export abstract class AbstractPool<
     if (tasksQueueOptions != null && !isPlainObject(tasksQueueOptions)) {
       throw new TypeError('Invalid tasks queue options: must be a plain object')
     }
-    if ((tasksQueueOptions?.concurrency as number) <= 0) {
+    if (
+      tasksQueueOptions?.concurrency != null &&
+      !Number.isSafeInteger(tasksQueueOptions.concurrency)
+    ) {
+      throw new TypeError(
+        'Invalid worker tasks concurrency: must be an integer'
+      )
+    }
+    if (
+      tasksQueueOptions?.concurrency != null &&
+      tasksQueueOptions.concurrency <= 0
+    ) {
       throw new Error(
-        `Invalid worker tasks concurrency '${
-          tasksQueueOptions.concurrency as number
-        }'`
+        `Invalid worker tasks concurrency '${tasksQueueOptions.concurrency}'`
       )
     }
   }
@@ -222,26 +240,41 @@ export abstract class AbstractPool<
       workerNodes: this.workerNodes.length,
       idleWorkerNodes: this.workerNodes.reduce(
         (accumulator, workerNode) =>
-          workerNode.tasksUsage.running === 0 ? accumulator + 1 : accumulator,
+          workerNode.workerUsage.tasks.executing === 0
+            ? accumulator + 1
+            : accumulator,
         0
       ),
       busyWorkerNodes: this.workerNodes.reduce(
         (accumulator, workerNode) =>
-          workerNode.tasksUsage.running > 0 ? accumulator + 1 : accumulator,
+          workerNode.workerUsage.tasks.executing > 0
+            ? accumulator + 1
+            : accumulator,
+        0
+      ),
+      executedTasks: this.workerNodes.reduce(
+        (accumulator, workerNode) =>
+          accumulator + workerNode.workerUsage.tasks.executed,
         0
       ),
-      runningTasks: this.workerNodes.reduce(
+      executingTasks: this.workerNodes.reduce(
         (accumulator, workerNode) =>
-          accumulator + workerNode.tasksUsage.running,
+          accumulator + workerNode.workerUsage.tasks.executing,
         0
       ),
       queuedTasks: this.workerNodes.reduce(
-        (accumulator, workerNode) => accumulator + workerNode.tasksQueue.size,
+        (accumulator, workerNode) =>
+          accumulator + workerNode.workerUsage.tasks.queued,
         0
       ),
       maxQueuedTasks: this.workerNodes.reduce(
         (accumulator, workerNode) =>
-          accumulator + workerNode.tasksQueue.maxSize,
+          accumulator + workerNode.workerUsage.tasks.maxQueued,
+        0
+      ),
+      failedTasks: this.workerNodes.reduce(
+        (accumulator, workerNode) =>
+          accumulator + workerNode.workerUsage.tasks.failed,
         0
       )
     }
@@ -294,21 +327,11 @@ export abstract class AbstractPool<
     if (workerChoiceStrategyOptions != null) {
       this.setWorkerChoiceStrategyOptions(workerChoiceStrategyOptions)
     }
-    for (const workerNode of this.workerNodes) {
-      this.setWorkerNodeTasksUsage(workerNode, {
-        ran: 0,
-        running: 0,
-        runTime: 0,
-        runTimeHistory: new CircularArray(),
-        avgRunTime: 0,
-        medRunTime: 0,
-        waitTime: 0,
-        waitTimeHistory: new CircularArray(),
-        avgWaitTime: 0,
-        medWaitTime: 0,
-        error: 0,
-        elu: undefined
-      })
+    for (const [workerNodeKey, workerNode] of this.workerNodes.entries()) {
+      this.setWorkerNodeTasksUsage(
+        workerNode,
+        this.getWorkerUsage(workerNodeKey)
+      )
       this.setWorkerStatistics(workerNode.worker)
     }
   }
@@ -371,10 +394,15 @@ export abstract class AbstractPool<
    */
   protected abstract get busy (): boolean
 
+  /**
+   * Whether worker nodes are executing at least one task.
+   *
+   * @returns Worker nodes busyness boolean status.
+   */
   protected internalBusy (): boolean {
     return (
       this.workerNodes.findIndex(workerNode => {
-        return workerNode.tasksUsage.running === 0
+        return workerNode.workerUsage.tasks.executing === 0
       }) === -1
     )
   }
@@ -400,7 +428,7 @@ export abstract class AbstractPool<
     if (
       this.opts.enableTasksQueue === true &&
       (this.busy ||
-        this.workerNodes[workerNodeKey].tasksUsage.running >=
+        this.workerNodes[workerNodeKey].workerUsage.tasks.executing >=
           ((this.opts.tasksQueueOptions as TasksQueueOptions)
             .concurrency as number))
     ) {
@@ -408,7 +436,6 @@ export abstract class AbstractPool<
     } else {
       this.executeTask(workerNodeKey, submittedTask)
     }
-    this.workerChoiceStrategyContext.update(workerNodeKey)
     this.checkAndEmitEvents()
     // eslint-disable-next-line @typescript-eslint/return-await
     return res
@@ -426,7 +453,7 @@ export abstract class AbstractPool<
   }
 
   /**
-   * Shutdowns the given worker.
+   * Terminates the given worker.
    *
    * @param worker - A worker within `workerNodes`.
    */
@@ -452,9 +479,15 @@ export abstract class AbstractPool<
    * Can be overridden.
    *
    * @param workerNodeKey - The worker node key.
+   * @param task - The task to execute.
    */
-  protected beforeTaskExecutionHook (workerNodeKey: number): void {
-    ++this.workerNodes[workerNodeKey].tasksUsage.running
+  protected beforeTaskExecutionHook (
+    workerNodeKey: number,
+    task: Task<Data>
+  ): void {
+    const workerUsage = this.workerNodes[workerNodeKey].workerUsage
+    ++workerUsage.tasks.executing
+    this.updateWaitTimeWorkerUsage(workerUsage, task)
   }
 
   /**
@@ -468,78 +501,126 @@ export abstract class AbstractPool<
     worker: Worker,
     message: MessageValue<Response>
   ): void {
-    const workerTasksUsage =
-      this.workerNodes[this.getWorkerNodeKey(worker)].tasksUsage
-    --workerTasksUsage.running
-    ++workerTasksUsage.ran
-    if (message.error != null) {
-      ++workerTasksUsage.error
+    const workerUsage =
+      this.workerNodes[this.getWorkerNodeKey(worker)].workerUsage
+    this.updateTaskStatisticsWorkerUsage(workerUsage, message)
+    this.updateRunTimeWorkerUsage(workerUsage, message)
+    this.updateEluWorkerUsage(workerUsage, message)
+  }
+
+  private updateTaskStatisticsWorkerUsage (
+    workerUsage: WorkerUsage,
+    message: MessageValue<Response>
+  ): void {
+    const workerTaskStatistics = workerUsage.tasks
+    --workerTaskStatistics.executing
+    ++workerTaskStatistics.executed
+    if (message.taskError != null) {
+      ++workerTaskStatistics.failed
     }
-    this.updateRunTimeTasksUsage(workerTasksUsage, message)
-    this.updateWaitTimeTasksUsage(workerTasksUsage, message)
-    this.updateEluTasksUsage(workerTasksUsage, message)
   }
 
-  private updateRunTimeTasksUsage (
-    workerTasksUsage: TasksUsage,
+  private updateRunTimeWorkerUsage (
+    workerUsage: WorkerUsage,
     message: MessageValue<Response>
   ): void {
-    if (this.workerChoiceStrategyContext.getTaskStatistics().runTime) {
-      workerTasksUsage.runTime += message.runTime ?? 0
+    if (
+      this.workerChoiceStrategyContext.getTaskStatisticsRequirements().runTime
+        .aggregate
+    ) {
+      workerUsage.runTime.aggregate += message.taskPerformance?.runTime ?? 0
       if (
-        this.workerChoiceStrategyContext.getTaskStatistics().avgRunTime &&
-        workerTasksUsage.ran !== 0
+        this.workerChoiceStrategyContext.getTaskStatisticsRequirements().runTime
+          .average &&
+        workerUsage.tasks.executed !== 0
       ) {
-        workerTasksUsage.avgRunTime =
-          workerTasksUsage.runTime / workerTasksUsage.ran
+        workerUsage.runTime.average =
+          workerUsage.runTime.aggregate /
+          (workerUsage.tasks.executed - workerUsage.tasks.failed)
       }
       if (
-        this.workerChoiceStrategyContext.getTaskStatistics().medRunTime &&
-        message.runTime != null
+        this.workerChoiceStrategyContext.getTaskStatisticsRequirements().runTime
+          .median &&
+        message.taskPerformance?.runTime != null
       ) {
-        workerTasksUsage.runTimeHistory.push(message.runTime)
-        workerTasksUsage.medRunTime = median(workerTasksUsage.runTimeHistory)
+        workerUsage.runTime.history.push(message.taskPerformance.runTime)
+        workerUsage.runTime.median = median(workerUsage.runTime.history)
       }
     }
   }
 
-  private updateWaitTimeTasksUsage (
-    workerTasksUsage: TasksUsage,
-    message: MessageValue<Response>
+  private updateWaitTimeWorkerUsage (
+    workerUsage: WorkerUsage,
+    task: Task<Data>
   ): void {
-    if (this.workerChoiceStrategyContext.getTaskStatistics().waitTime) {
-      workerTasksUsage.waitTime += message.waitTime ?? 0
+    const timestamp = performance.now()
+    const taskWaitTime = timestamp - (task.timestamp ?? timestamp)
+    if (
+      this.workerChoiceStrategyContext.getTaskStatisticsRequirements().waitTime
+        .aggregate
+    ) {
+      workerUsage.waitTime.aggregate += taskWaitTime ?? 0
       if (
-        this.workerChoiceStrategyContext.getTaskStatistics().avgWaitTime &&
-        workerTasksUsage.ran !== 0
+        this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
+          .waitTime.average &&
+        workerUsage.tasks.executed !== 0
       ) {
-        workerTasksUsage.avgWaitTime =
-          workerTasksUsage.waitTime / workerTasksUsage.ran
+        workerUsage.waitTime.average =
+          workerUsage.waitTime.aggregate /
+          (workerUsage.tasks.executed - workerUsage.tasks.failed)
       }
       if (
-        this.workerChoiceStrategyContext.getTaskStatistics().medWaitTime &&
-        message.waitTime != null
+        this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
+          .waitTime.median &&
+        taskWaitTime != null
       ) {
-        workerTasksUsage.waitTimeHistory.push(message.waitTime)
-        workerTasksUsage.medWaitTime = median(workerTasksUsage.waitTimeHistory)
+        workerUsage.waitTime.history.push(taskWaitTime)
+        workerUsage.waitTime.median = median(workerUsage.waitTime.history)
       }
     }
   }
 
-  private updateEluTasksUsage (
-    workerTasksUsage: TasksUsage,
+  private updateEluWorkerUsage (
+    workerUsage: WorkerUsage,
     message: MessageValue<Response>
   ): void {
-    if (this.workerChoiceStrategyContext.getTaskStatistics().elu) {
-      if (workerTasksUsage.elu != null && message.elu != null) {
-        workerTasksUsage.elu = {
-          idle: workerTasksUsage.elu.idle + message.elu.idle,
-          active: workerTasksUsage.elu.active + message.elu.active,
-          utilization:
-            (workerTasksUsage.elu.utilization + message.elu.utilization) / 2
-        }
-      } else if (message.elu != null) {
-        workerTasksUsage.elu = message.elu
+    if (
+      this.workerChoiceStrategyContext.getTaskStatisticsRequirements().elu
+        .aggregate
+    ) {
+      if (workerUsage.elu != null && message.taskPerformance?.elu != null) {
+        workerUsage.elu.idle.aggregate += message.taskPerformance.elu.idle
+        workerUsage.elu.active.aggregate += message.taskPerformance.elu.active
+        workerUsage.elu.utilization =
+          (workerUsage.elu.utilization +
+            message.taskPerformance.elu.utilization) /
+          2
+      } else if (message.taskPerformance?.elu != null) {
+        workerUsage.elu.idle.aggregate = message.taskPerformance.elu.idle
+        workerUsage.elu.active.aggregate = message.taskPerformance.elu.active
+        workerUsage.elu.utilization = message.taskPerformance.elu.utilization
+      }
+      if (
+        this.workerChoiceStrategyContext.getTaskStatisticsRequirements().elu
+          .average &&
+        workerUsage.tasks.executed !== 0
+      ) {
+        const executedTasks =
+          workerUsage.tasks.executed - workerUsage.tasks.failed
+        workerUsage.elu.idle.average =
+          workerUsage.elu.idle.aggregate / executedTasks
+        workerUsage.elu.active.average =
+          workerUsage.elu.active.aggregate / executedTasks
+      }
+      if (
+        this.workerChoiceStrategyContext.getTaskStatisticsRequirements().elu
+          .median &&
+        message.taskPerformance?.elu != null
+      ) {
+        workerUsage.elu.idle.history.push(message.taskPerformance.elu.idle)
+        workerUsage.elu.active.history.push(message.taskPerformance.elu.active)
+        workerUsage.elu.idle.median = median(workerUsage.elu.idle.history)
+        workerUsage.elu.active.median = median(workerUsage.elu.active.history)
       }
     }
   }
@@ -547,32 +628,29 @@ export abstract class AbstractPool<
   /**
    * Chooses a worker node for the next task.
    *
-   * The default worker choice strategy uses a round robin algorithm to distribute the load.
+   * The default worker choice strategy uses a round robin algorithm to distribute the tasks.
    *
    * @returns The worker node key
    */
-  protected chooseWorkerNode (): number {
-    let workerNodeKey: number
-    if (this.type === PoolTypes.dynamic && !this.full && this.internalBusy()) {
-      const workerCreated = this.createAndSetupWorker()
-      this.registerWorkerMessageListener(workerCreated, message => {
-        const currentWorkerNodeKey = this.getWorkerNodeKey(workerCreated)
-        if (
-          isKillBehavior(KillBehaviors.HARD, message.kill) ||
-          (message.kill != null &&
-            this.workerNodes[currentWorkerNodeKey].tasksUsage.running === 0)
-        ) {
-          // Kill message received from the worker: no new tasks are submitted to that worker for a while ( > maxInactiveTime)
-          this.flushTasksQueue(currentWorkerNodeKey)
-          // FIXME: wait for tasks to be finished
-          void (this.destroyWorker(workerCreated) as Promise<void>)
-        }
-      })
-      workerNodeKey = this.getWorkerNodeKey(workerCreated)
-    } else {
-      workerNodeKey = this.workerChoiceStrategyContext.execute()
+  private chooseWorkerNode (): number {
+    if (this.shallCreateDynamicWorker()) {
+      const worker = this.createAndSetupDynamicWorker()
+      if (
+        this.workerChoiceStrategyContext.getStrategyPolicy().useDynamicWorker
+      ) {
+        return this.getWorkerNodeKey(worker)
+      }
     }
-    return workerNodeKey
+    return this.workerChoiceStrategyContext.execute()
+  }
+
+  /**
+   * Conditions for dynamic worker creation.
+   *
+   * @returns Whether to create a dynamic worker or not.
+   */
+  private shallCreateDynamicWorker (): boolean {
+    return this.type === PoolTypes.dynamic && !this.full && this.internalBusy()
   }
 
   /**
@@ -597,7 +675,9 @@ export abstract class AbstractPool<
   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 
   /**
-   * Returns a newly created worker.
+   * Creates a new worker.
+   *
+   * @returns Newly created worker.
    */
   protected abstract createWorker (): Worker
 
@@ -624,8 +704,6 @@ export abstract class AbstractPool<
       if (this.emitter != null) {
         this.emitter.emit(PoolEvents.error, error)
       }
-    })
-    worker.on('error', () => {
       if (this.opts.restartWorkerOnError === true) {
         this.createAndSetupWorker()
       }
@@ -645,6 +723,33 @@ export abstract class AbstractPool<
     return worker
   }
 
+  /**
+   * Creates a new dynamic worker and sets it up completely in the pool worker nodes.
+   *
+   * @returns New, completely set up dynamic worker.
+   */
+  protected createAndSetupDynamicWorker (): Worker {
+    const worker = this.createAndSetupWorker()
+    this.registerWorkerMessageListener(worker, message => {
+      const workerNodeKey = this.getWorkerNodeKey(worker)
+      if (
+        isKillBehavior(KillBehaviors.HARD, message.kill) ||
+        (message.kill != null &&
+          ((this.opts.enableTasksQueue === false &&
+            this.workerNodes[workerNodeKey].workerUsage.tasks.executing ===
+              0) ||
+            (this.opts.enableTasksQueue === true &&
+              this.workerNodes[workerNodeKey].workerUsage.tasks.executing ===
+                0 &&
+              this.tasksQueueSize(workerNodeKey) === 0)))
+      ) {
+        // Kill message received from the worker: no new tasks are submitted to that worker for a while ( > maxInactiveTime)
+        void (this.destroyWorker(worker) as Promise<void>)
+      }
+    })
+    return worker
+  }
+
   /**
    * This function is the listener registered for each worker message.
    *
@@ -656,14 +761,11 @@ export abstract class AbstractPool<
         // Task execution response received
         const promiseResponse = this.promiseResponseMap.get(message.id)
         if (promiseResponse != null) {
-          if (message.error != null) {
-            promiseResponse.reject(message.error)
+          if (message.taskError != null) {
             if (this.emitter != null) {
-              this.emitter.emit(PoolEvents.taskError, {
-                error: message.error,
-                errorData: message.errorData
-              })
+              this.emitter.emit(PoolEvents.taskError, message.taskError)
             }
+            promiseResponse.reject(message.taskError.message)
           } else {
             promiseResponse.resolve(message.data as Response)
           }
@@ -679,6 +781,7 @@ export abstract class AbstractPool<
               this.dequeueTask(workerNodeKey) as Task<Data>
             )
           }
+          this.workerChoiceStrategyContext.update(workerNodeKey)
         }
       }
     }
@@ -699,13 +802,13 @@ export abstract class AbstractPool<
    * Sets the given worker node its tasks usage in the pool.
    *
    * @param workerNode - The worker node.
-   * @param tasksUsage - The worker node tasks usage.
+   * @param workerUsage - The worker usage.
    */
   private setWorkerNodeTasksUsage (
     workerNode: WorkerNode<Worker, Data>,
-    tasksUsage: TasksUsage
+    workerUsage: WorkerUsage
   ): void {
-    workerNode.tasksUsage = tasksUsage
+    workerNode.workerUsage = workerUsage
   }
 
   /**
@@ -715,46 +818,39 @@ export abstract class AbstractPool<
    * @returns The worker nodes length.
    */
   private pushWorkerNode (worker: Worker): number {
-    return this.workerNodes.push({
+    this.workerNodes.push({
       worker,
-      tasksUsage: {
-        ran: 0,
-        running: 0,
-        runTime: 0,
-        runTimeHistory: new CircularArray(),
-        avgRunTime: 0,
-        medRunTime: 0,
-        waitTime: 0,
-        waitTimeHistory: new CircularArray(),
-        avgWaitTime: 0,
-        medWaitTime: 0,
-        error: 0,
-        elu: undefined
-      },
+      workerUsage: this.getWorkerUsage(),
       tasksQueue: new Queue<Task<Data>>()
     })
-  }
-
-  /**
-   * Sets the given worker in the pool worker nodes.
-   *
-   * @param workerNodeKey - The worker node key.
-   * @param worker - The worker.
-   * @param tasksUsage - The worker tasks usage.
-   * @param tasksQueue - The worker task queue.
-   */
-  private setWorkerNode (
-    workerNodeKey: number,
-    worker: Worker,
-    tasksUsage: TasksUsage,
-    tasksQueue: Queue<Task<Data>>
-  ): void {
-    this.workerNodes[workerNodeKey] = {
-      worker,
-      tasksUsage,
-      tasksQueue
-    }
-  }
+    const workerNodeKey = this.getWorkerNodeKey(worker)
+    this.setWorkerNodeTasksUsage(
+      this.workerNodes[workerNodeKey],
+      this.getWorkerUsage(workerNodeKey)
+    )
+    return this.workerNodes.length
+  }
+
+  // /**
+  //  * Sets the given worker in the pool worker nodes.
+  //  *
+  //  * @param workerNodeKey - The worker node key.
+  //  * @param worker - The worker.
+  //  * @param workerUsage - The worker usage.
+  //  * @param tasksQueue - The worker task queue.
+  //  */
+  // private setWorkerNode (
+  //   workerNodeKey: number,
+  //   worker: Worker,
+  //   workerUsage: WorkerUsage,
+  //   tasksQueue: Queue<Task<Data>>
+  // ): void {
+  //   this.workerNodes[workerNodeKey] = {
+  //     worker,
+  //     workerUsage,
+  //     tasksQueue
+  //   }
+  // }
 
   /**
    * Removes the given worker from the pool worker nodes.
@@ -770,7 +866,7 @@ export abstract class AbstractPool<
   }
 
   private executeTask (workerNodeKey: number, task: Task<Data>): void {
-    this.beforeTaskExecutionHook(workerNodeKey)
+    this.beforeTaskExecutionHook(workerNodeKey, task)
     this.sendToWorker(this.workerNodes[workerNodeKey].worker, task)
   }
 
@@ -786,6 +882,10 @@ export abstract class AbstractPool<
     return this.workerNodes[workerNodeKey].tasksQueue.size
   }
 
+  private tasksMaxQueueSize (workerNodeKey: number): number {
+    return this.workerNodes[workerNodeKey].tasksQueue.maxSize
+  }
+
   private flushTasksQueue (workerNodeKey: number): void {
     if (this.tasksQueueSize(workerNodeKey) > 0) {
       for (let i = 0; i < this.tasksQueueSize(workerNodeKey); i++) {
@@ -795,6 +895,7 @@ export abstract class AbstractPool<
         )
       }
     }
+    this.workerNodes[workerNodeKey].tasksQueue.clear()
   }
 
   private flushTasksQueues (): void {
@@ -806,10 +907,61 @@ export abstract class AbstractPool<
   private setWorkerStatistics (worker: Worker): void {
     this.sendToWorker(worker, {
       statistics: {
-        runTime: this.workerChoiceStrategyContext.getTaskStatistics().runTime,
-        waitTime: this.workerChoiceStrategyContext.getTaskStatistics().waitTime,
-        elu: this.workerChoiceStrategyContext.getTaskStatistics().elu
+        runTime:
+          this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
+            .runTime.aggregate,
+        elu: this.workerChoiceStrategyContext.getTaskStatisticsRequirements()
+          .elu.aggregate
       }
     })
   }
+
+  private getWorkerUsage (workerNodeKey?: number): WorkerUsage {
+    const getTasksQueueSize = (workerNodeKey?: number): number => {
+      return workerNodeKey != null ? this.tasksQueueSize(workerNodeKey) : 0
+    }
+    const getTasksMaxQueueSize = (workerNodeKey?: number): number => {
+      return workerNodeKey != null ? this.tasksMaxQueueSize(workerNodeKey) : 0
+    }
+    return {
+      tasks: {
+        executed: 0,
+        executing: 0,
+        get queued (): number {
+          return getTasksQueueSize(workerNodeKey)
+        },
+        get maxQueued (): number {
+          return getTasksMaxQueueSize(workerNodeKey)
+        },
+        failed: 0
+      },
+      runTime: {
+        aggregate: 0,
+        average: 0,
+        median: 0,
+        history: new CircularArray()
+      },
+      waitTime: {
+        aggregate: 0,
+        average: 0,
+        median: 0,
+        history: new CircularArray()
+      },
+      elu: {
+        idle: {
+          aggregate: 0,
+          average: 0,
+          median: 0,
+          history: new CircularArray()
+        },
+        active: {
+          aggregate: 0,
+          average: 0,
+          median: 0,
+          history: new CircularArray()
+        },
+        utilization: 0
+      }
+    }
+  }
 }