src/pools/abstract-pool.ts

   1 import crypto from 'node:crypto'
   2 import type { MessageValue, PromiseResponseWrapper } from '../utility-types'
   3 import {
   4   DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS,
   5   EMPTY_FUNCTION,
   6   isPlainObject,
   7   median
   8 } from '../utils'
   9 import { KillBehaviors, isKillBehavior } from '../worker/worker-options'
  10 import { CircularArray } from '../circular-array'
  11 import { Queue } from '../queue'
  12 import {
  13   type IPool,
  14   PoolEmitter,
  15   PoolEvents,
  16   type PoolOptions,
  17   PoolType,
  18   type TasksQueueOptions
  19 } from './pool'
  20 import type { IWorker, Task, TasksUsage, WorkerNode } from './worker'
  21 import {
  22   WorkerChoiceStrategies,
  23   type WorkerChoiceStrategy,
  24   type WorkerChoiceStrategyOptions
  25 } from './selection-strategies/selection-strategies-types'
  26 import { WorkerChoiceStrategyContext } from './selection-strategies/worker-choice-strategy-context'
  27
  28 /**
  29  * Base class that implements some shared logic for all poolifier pools.
  30  *
  31  * @typeParam Worker - Type of worker which manages this pool.
  32  * @typeParam Data - Type of data sent to the worker. This can only be serializable data.
  33  * @typeParam Response - Type of execution response. This can only be serializable data.
  34  */
  35 export abstract class AbstractPool<
  36   Worker extends IWorker,
  37   Data = unknown,
  38   Response = unknown
  39 > implements IPool<Worker, Data, Response> {
  40   /** @inheritDoc */
  41   public readonly workerNodes: Array<WorkerNode<Worker, Data>> = []
  42
  43   /** @inheritDoc */
  44   public readonly emitter?: PoolEmitter
  45
  46   /**
  47    * The execution response promise map.
  48    *
  49    * - `key`: The message id of each submitted task.
  50    * - `value`: An object that contains the worker, the execution response promise resolve and reject callbacks.
  51    *
  52    * When we receive a message from the worker, we get a map entry with the promise resolve/reject bound to the message id.
  53    */
  54   protected promiseResponseMap: Map<
  55   string,
  56   PromiseResponseWrapper<Worker, Response>
  57   > = new Map<string, PromiseResponseWrapper<Worker, Response>>()
  58
  59   /**
  60    * Worker choice strategy context referencing a worker choice algorithm implementation.
  61    *
  62    * Default to a round robin algorithm.
  63    */
  64   protected workerChoiceStrategyContext: WorkerChoiceStrategyContext<
  65   Worker,
  66   Data,
  67   Response
  68   >
  69
  70   /**
  71    * Constructs a new poolifier pool.
  72    *
  73    * @param numberOfWorkers - Number of workers that this pool should manage.
  74    * @param filePath - Path to the worker file.
  75    * @param opts - Options for the pool.
  76    */
  77   public constructor (
  78     public readonly numberOfWorkers: number,
  79     public readonly filePath: string,
  80     public readonly opts: PoolOptions<Worker>
  81   ) {
  82     if (!this.isMain()) {
  83       throw new Error('Cannot start a pool from a worker!')
  84     }
  85     this.checkNumberOfWorkers(this.numberOfWorkers)
  86     this.checkFilePath(this.filePath)
  87     this.checkPoolOptions(this.opts)
  88
  89     this.chooseWorkerNode = this.chooseWorkerNode.bind(this)
  90     this.executeTask = this.executeTask.bind(this)
  91     this.enqueueTask = this.enqueueTask.bind(this)
  92     this.checkAndEmitEvents = this.checkAndEmitEvents.bind(this)
  93
  94     this.setupHook()
  95
  96     for (let i = 1; i <= this.numberOfWorkers; i++) {
  97       this.createAndSetupWorker()
  98     }
  99
 100     if (this.opts.enableEvents === true) {
 101       this.emitter = new PoolEmitter()
 102     }
 103     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext<
 104     Worker,
 105     Data,
 106     Response
 107     >(
 108       this,
 109       this.opts.workerChoiceStrategy,
 110       this.opts.workerChoiceStrategyOptions
 111     )
 112   }
 113
 114   private checkFilePath (filePath: string): void {
 115     if (
 116       filePath == null ||
 117       (typeof filePath === 'string' && filePath.trim().length === 0)
 118     ) {
 119       throw new Error('Please specify a file with a worker implementation')
 120     }
 121   }
 122
 123   private checkNumberOfWorkers (numberOfWorkers: number): void {
 124     if (numberOfWorkers == null) {
 125       throw new Error(
 126         'Cannot instantiate a pool without specifying the number of workers'
 127       )
 128     } else if (!Number.isSafeInteger(numberOfWorkers)) {
 129       throw new TypeError(
 130         'Cannot instantiate a pool with a non safe integer number of workers'
 131       )
 132     } else if (numberOfWorkers < 0) {
 133       throw new RangeError(
 134         'Cannot instantiate a pool with a negative number of workers'
 135       )
 136     } else if (this.type === PoolType.FIXED && numberOfWorkers === 0) {
 137       throw new Error('Cannot instantiate a fixed pool with no worker')
 138     }
 139   }
 140
 141   private checkPoolOptions (opts: PoolOptions<Worker>): void {
 142     if (isPlainObject(opts)) {
 143       this.opts.workerChoiceStrategy =
 144         opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
 145       this.checkValidWorkerChoiceStrategy(this.opts.workerChoiceStrategy)
 146       this.opts.workerChoiceStrategyOptions =
 147         opts.workerChoiceStrategyOptions ??
 148         DEFAULT_WORKER_CHOICE_STRATEGY_OPTIONS
 149       this.opts.enableEvents = opts.enableEvents ?? true
 150       this.opts.enableTasksQueue = opts.enableTasksQueue ?? false
 151       if (this.opts.enableTasksQueue) {
 152         this.checkValidTasksQueueOptions(
 153           opts.tasksQueueOptions as TasksQueueOptions
 154         )
 155         this.opts.tasksQueueOptions = this.buildTasksQueueOptions(
 156           opts.tasksQueueOptions as TasksQueueOptions
 157         )
 158       }
 159     } else {
 160       throw new TypeError('Invalid pool options: must be a plain object')
 161     }
 162   }
 163
 164   private checkValidWorkerChoiceStrategy (
 165     workerChoiceStrategy: WorkerChoiceStrategy
 166   ): void {
 167     if (!Object.values(WorkerChoiceStrategies).includes(workerChoiceStrategy)) {
 168       throw new Error(
 169         `Invalid worker choice strategy '${workerChoiceStrategy}'`
 170       )
 171     }
 172   }
 173
 174   private checkValidWorkerChoiceStrategyOptions (
 175     workerChoiceStrategyOptions: WorkerChoiceStrategyOptions
 176   ): void {
 177     if (!isPlainObject(workerChoiceStrategyOptions)) {
 178       throw new TypeError(
 179         'Invalid worker choice strategy options: must be a plain object'
 180       )
 181     }
 182   }
 183
 184   private checkValidTasksQueueOptions (
 185     tasksQueueOptions: TasksQueueOptions
 186   ): void {
 187     if (tasksQueueOptions != null && !isPlainObject(tasksQueueOptions)) {
 188       throw new TypeError('Invalid tasks queue options: must be a plain object')
 189     }
 190     if ((tasksQueueOptions?.concurrency as number) <= 0) {
 191       throw new Error(
 192         `Invalid worker tasks concurrency '${
 193           tasksQueueOptions.concurrency as number
 194         }'`
 195       )
 196     }
 197   }
 198
 199   /** @inheritDoc */
 200   public abstract get type (): PoolType
 201
 202   /** @inheritDoc */
 203   public abstract get size (): number
 204
 205   /**
 206    * Number of tasks running in the pool.
 207    */
 208   private get numberOfRunningTasks (): number {
 209     return this.workerNodes.reduce(
 210       (accumulator, workerNode) => accumulator + workerNode.tasksUsage.running,
 211       0
 212     )
 213   }
 214
 215   /**
 216    * Number of tasks queued in the pool.
 217    */
 218   private get numberOfQueuedTasks (): number {
 219     if (this.opts.enableTasksQueue === false) {
 220       return 0
 221     }
 222     return this.workerNodes.reduce(
 223       (accumulator, workerNode) => accumulator + workerNode.tasksQueue.size,
 224       0
 225     )
 226   }
 227
 228   /**
 229    * Gets the given worker its worker node key.
 230    *
 231    * @param worker - The worker.
 232    * @returns The worker node key if the worker is found in the pool worker nodes, `-1` otherwise.
 233    */
 234   private getWorkerNodeKey (worker: Worker): number {
 235     return this.workerNodes.findIndex(
 236       workerNode => workerNode.worker === worker
 237     )
 238   }
 239
 240   /** @inheritDoc */
 241   public setWorkerChoiceStrategy (
 242     workerChoiceStrategy: WorkerChoiceStrategy,
 243     workerChoiceStrategyOptions?: WorkerChoiceStrategyOptions
 244   ): void {
 245     this.checkValidWorkerChoiceStrategy(workerChoiceStrategy)
 246     this.opts.workerChoiceStrategy = workerChoiceStrategy
 247     for (const workerNode of this.workerNodes) {
 248       this.setWorkerNodeTasksUsage(workerNode, {
 249         run: 0,
 250         running: 0,
 251         runTime: 0,
 252         runTimeHistory: new CircularArray(),
 253         avgRunTime: 0,
 254         medRunTime: 0,
 255         error: 0
 256       })
 257     }
 258     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 259       this.opts.workerChoiceStrategy
 260     )
 261     if (workerChoiceStrategyOptions != null) {
 262       this.setWorkerChoiceStrategyOptions(workerChoiceStrategyOptions)
 263     }
 264   }
 265
 266   /** @inheritDoc */
 267   public setWorkerChoiceStrategyOptions (
 268     workerChoiceStrategyOptions: WorkerChoiceStrategyOptions
 269   ): void {
 270     this.checkValidWorkerChoiceStrategyOptions(workerChoiceStrategyOptions)
 271     this.opts.workerChoiceStrategyOptions = workerChoiceStrategyOptions
 272     this.workerChoiceStrategyContext.setOptions(
 273       this.opts.workerChoiceStrategyOptions
 274     )
 275   }
 276
 277   /** @inheritDoc */
 278   public enableTasksQueue (
 279     enable: boolean,
 280     tasksQueueOptions?: TasksQueueOptions
 281   ): void {
 282     if (this.opts.enableTasksQueue === true && !enable) {
 283       this.flushTasksQueues()
 284     }
 285     this.opts.enableTasksQueue = enable
 286     this.setTasksQueueOptions(tasksQueueOptions as TasksQueueOptions)
 287   }
 288
 289   /** @inheritDoc */
 290   public setTasksQueueOptions (tasksQueueOptions: TasksQueueOptions): void {
 291     if (this.opts.enableTasksQueue === true) {
 292       this.checkValidTasksQueueOptions(tasksQueueOptions)
 293       this.opts.tasksQueueOptions =
 294         this.buildTasksQueueOptions(tasksQueueOptions)
 295     } else {
 296       delete this.opts.tasksQueueOptions
 297     }
 298   }
 299
 300   private buildTasksQueueOptions (
 301     tasksQueueOptions: TasksQueueOptions
 302   ): TasksQueueOptions {
 303     return {
 304       concurrency: tasksQueueOptions?.concurrency ?? 1
 305     }
 306   }
 307
 308   /**
 309    * Whether the pool is full or not.
 310    *
 311    * The pool filling boolean status.
 312    */
 313   protected abstract get full (): boolean
 314
 315   /**
 316    * Whether the pool is busy or not.
 317    *
 318    * The pool busyness boolean status.
 319    */
 320   protected abstract get busy (): boolean
 321
 322   protected internalBusy (): boolean {
 323     return (
 324       this.workerNodes.findIndex(workerNode => {
 325         return workerNode.tasksUsage?.running === 0
 326       }) === -1
 327     )
 328   }
 329
 330   /** @inheritDoc */
 331   public async execute (data?: Data, name?: string): Promise<Response> {
 332     const [workerNodeKey, workerNode] = this.chooseWorkerNode()
 333     const submittedTask: Task<Data> = {
 334       name,
 335       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 336       data: data ?? ({} as Data),
 337       id: crypto.randomUUID()
 338     }
 339     const res = new Promise<Response>((resolve, reject) => {
 340       this.promiseResponseMap.set(submittedTask.id as string, {
 341         resolve,
 342         reject,
 343         worker: workerNode.worker
 344       })
 345     })
 346     if (
 347       this.opts.enableTasksQueue === true &&
 348       (this.busy ||
 349         this.workerNodes[workerNodeKey].tasksUsage.running >=
 350           ((this.opts.tasksQueueOptions as TasksQueueOptions)
 351             .concurrency as number))
 352     ) {
 353       this.enqueueTask(workerNodeKey, submittedTask)
 354     } else {
 355       this.executeTask(workerNodeKey, submittedTask)
 356     }
 357     this.checkAndEmitEvents()
 358     // eslint-disable-next-line @typescript-eslint/return-await
 359     return res
 360   }
 361
 362   /** @inheritDoc */
 363   public async destroy (): Promise<void> {
 364     await Promise.all(
 365       this.workerNodes.map(async (workerNode, workerNodeKey) => {
 366         this.flushTasksQueue(workerNodeKey)
 367         await this.destroyWorker(workerNode.worker)
 368       })
 369     )
 370   }
 371
 372   /**
 373    * Shutdowns the given worker.
 374    *
 375    * @param worker - A worker within `workerNodes`.
 376    */
 377   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 378
 379   /**
 380    * Setup hook to execute code before worker node are created in the abstract constructor.
 381    * Can be overridden
 382    *
 383    * @virtual
 384    */
 385   protected setupHook (): void {
 386     // Intentionally empty
 387   }
 388
 389   /**
 390    * Should return whether the worker is the main worker or not.
 391    */
 392   protected abstract isMain (): boolean
 393
 394   /**
 395    * Hook executed before the worker task execution.
 396    * Can be overridden.
 397    *
 398    * @param workerNodeKey - The worker node key.
 399    */
 400   protected beforeTaskExecutionHook (workerNodeKey: number): void {
 401     ++this.workerNodes[workerNodeKey].tasksUsage.running
 402   }
 403
 404   /**
 405    * Hook executed after the worker task execution.
 406    * Can be overridden.
 407    *
 408    * @param worker - The worker.
 409    * @param message - The received message.
 410    */
 411   protected afterTaskExecutionHook (
 412     worker: Worker,
 413     message: MessageValue<Response>
 414   ): void {
 415     const workerTasksUsage = this.getWorkerTasksUsage(worker)
 416     --workerTasksUsage.running
 417     ++workerTasksUsage.run
 418     if (message.error != null) {
 419       ++workerTasksUsage.error
 420     }
 421     if (this.workerChoiceStrategyContext.getRequiredStatistics().runTime) {
 422       workerTasksUsage.runTime += message.runTime ?? 0
 423       if (
 424         this.workerChoiceStrategyContext.getRequiredStatistics().avgRunTime &&
 425         workerTasksUsage.run !== 0
 426       ) {
 427         workerTasksUsage.avgRunTime =
 428           workerTasksUsage.runTime / workerTasksUsage.run
 429       }
 430       if (this.workerChoiceStrategyContext.getRequiredStatistics().medRunTime) {
 431         workerTasksUsage.runTimeHistory.push(message.runTime ?? 0)
 432         workerTasksUsage.medRunTime = median(workerTasksUsage.runTimeHistory)
 433       }
 434     }
 435   }
 436
 437   /**
 438    * Chooses a worker node for the next task.
 439    *
 440    * The default uses a round robin algorithm to distribute the load.
 441    *
 442    * @returns [worker node key, worker node].
 443    */
 444   protected chooseWorkerNode (): [number, WorkerNode<Worker, Data>] {
 445     let workerNodeKey: number
 446     if (this.type === PoolType.DYNAMIC && !this.full && this.internalBusy()) {
 447       const workerCreated = this.createAndSetupWorker()
 448       this.registerWorkerMessageListener(workerCreated, message => {
 449         if (
 450           isKillBehavior(KillBehaviors.HARD, message.kill) ||
 451           (message.kill != null &&
 452             this.getWorkerTasksUsage(workerCreated)?.running === 0)
 453         ) {
 454           // Kill message received from the worker: no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 455           this.flushTasksQueueByWorker(workerCreated)
 456           void (this.destroyWorker(workerCreated) as Promise<void>)
 457         }
 458       })
 459       workerNodeKey = this.getWorkerNodeKey(workerCreated)
 460     } else {
 461       workerNodeKey = this.workerChoiceStrategyContext.execute()
 462     }
 463     return [workerNodeKey, this.workerNodes[workerNodeKey]]
 464   }
 465
 466   /**
 467    * Sends a message to the given worker.
 468    *
 469    * @param worker - The worker which should receive the message.
 470    * @param message - The message.
 471    */
 472   protected abstract sendToWorker (
 473     worker: Worker,
 474     message: MessageValue<Data>
 475   ): void
 476
 477   /**
 478    * Registers a listener callback on the given worker.
 479    *
 480    * @param worker - The worker which should register a listener.
 481    * @param listener - The message listener callback.
 482    */
 483   protected abstract registerWorkerMessageListener<
 484     Message extends Data | Response
 485   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 486
 487   /**
 488    * Returns a newly created worker.
 489    */
 490   protected abstract createWorker (): Worker
 491
 492   /**
 493    * Function that can be hooked up when a worker has been newly created and moved to the pool worker nodes.
 494    *
 495    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 496    *
 497    * @param worker - The newly created worker.
 498    */
 499   protected abstract afterWorkerSetup (worker: Worker): void
 500
 501   /**
 502    * Creates a new worker and sets it up completely in the pool worker nodes.
 503    *
 504    * @returns New, completely set up worker.
 505    */
 506   protected createAndSetupWorker (): Worker {
 507     const worker = this.createWorker()
 508
 509     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 510     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 511     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 512     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 513     worker.once('exit', () => {
 514       this.removeWorkerNode(worker)
 515     })
 516
 517     this.pushWorkerNode(worker)
 518
 519     this.afterWorkerSetup(worker)
 520
 521     return worker
 522   }
 523
 524   /**
 525    * This function is the listener registered for each worker message.
 526    *
 527    * @returns The listener function to execute when a message is received from a worker.
 528    */
 529   protected workerListener (): (message: MessageValue<Response>) => void {
 530     return message => {
 531       if (message.id != null) {
 532         // Task execution response received
 533         const promiseResponse = this.promiseResponseMap.get(message.id)
 534         if (promiseResponse != null) {
 535           if (message.error != null) {
 536             promiseResponse.reject(message.error)
 537           } else {
 538             promiseResponse.resolve(message.data as Response)
 539           }
 540           this.afterTaskExecutionHook(promiseResponse.worker, message)
 541           this.promiseResponseMap.delete(message.id)
 542           const workerNodeKey = this.getWorkerNodeKey(promiseResponse.worker)
 543           if (
 544             this.opts.enableTasksQueue === true &&
 545             this.tasksQueueSize(workerNodeKey) > 0
 546           ) {
 547             this.executeTask(
 548               workerNodeKey,
 549               this.dequeueTask(workerNodeKey) as Task<Data>
 550             )
 551           }
 552         }
 553       }
 554     }
 555   }
 556
 557   private checkAndEmitEvents (): void {
 558     if (this.opts.enableEvents === true) {
 559       if (this.busy) {
 560         this.emitter?.emit(PoolEvents.busy)
 561       }
 562       if (this.type === PoolType.DYNAMIC && this.full) {
 563         this.emitter?.emit(PoolEvents.full)
 564       }
 565     }
 566   }
 567
 568   /**
 569    * Sets the given worker node its tasks usage in the pool.
 570    *
 571    * @param workerNode - The worker node.
 572    * @param tasksUsage - The worker node tasks usage.
 573    */
 574   private setWorkerNodeTasksUsage (
 575     workerNode: WorkerNode<Worker, Data>,
 576     tasksUsage: TasksUsage
 577   ): void {
 578     workerNode.tasksUsage = tasksUsage
 579   }
 580
 581   /**
 582    * Gets the given worker its tasks usage in the pool.
 583    *
 584    * @param worker - The worker.
 585    * @throws Error if the worker is not found in the pool worker nodes.
 586    * @returns The worker tasks usage.
 587    */
 588   private getWorkerTasksUsage (worker: Worker): TasksUsage {
 589     const workerNodeKey = this.getWorkerNodeKey(worker)
 590     if (workerNodeKey !== -1) {
 591       return this.workerNodes[workerNodeKey].tasksUsage
 592     }
 593     throw new Error('Worker could not be found in the pool worker nodes')
 594   }
 595
 596   /**
 597    * Pushes the given worker in the pool worker nodes.
 598    *
 599    * @param worker - The worker.
 600    * @returns The worker nodes length.
 601    */
 602   private pushWorkerNode (worker: Worker): number {
 603     return this.workerNodes.push({
 604       worker,
 605       tasksUsage: {
 606         run: 0,
 607         running: 0,
 608         runTime: 0,
 609         runTimeHistory: new CircularArray(),
 610         avgRunTime: 0,
 611         medRunTime: 0,
 612         error: 0
 613       },
 614       tasksQueue: new Queue<Task<Data>>()
 615     })
 616   }
 617
 618   /**
 619    * Sets the given worker in the pool worker nodes.
 620    *
 621    * @param workerNodeKey - The worker node key.
 622    * @param worker - The worker.
 623    * @param tasksUsage - The worker tasks usage.
 624    * @param tasksQueue - The worker task queue.
 625    */
 626   private setWorkerNode (
 627     workerNodeKey: number,
 628     worker: Worker,
 629     tasksUsage: TasksUsage,
 630     tasksQueue: Queue<Task<Data>>
 631   ): void {
 632     this.workerNodes[workerNodeKey] = {
 633       worker,
 634       tasksUsage,
 635       tasksQueue
 636     }
 637   }
 638
 639   /**
 640    * Removes the given worker from the pool worker nodes.
 641    *
 642    * @param worker - The worker.
 643    */
 644   private removeWorkerNode (worker: Worker): void {
 645     const workerNodeKey = this.getWorkerNodeKey(worker)
 646     this.workerNodes.splice(workerNodeKey, 1)
 647     this.workerChoiceStrategyContext.remove(workerNodeKey)
 648   }
 649
 650   private executeTask (workerNodeKey: number, task: Task<Data>): void {
 651     this.beforeTaskExecutionHook(workerNodeKey)
 652     this.sendToWorker(this.workerNodes[workerNodeKey].worker, task)
 653   }
 654
 655   private enqueueTask (workerNodeKey: number, task: Task<Data>): number {
 656     return this.workerNodes[workerNodeKey].tasksQueue.enqueue(task)
 657   }
 658
 659   private dequeueTask (workerNodeKey: number): Task<Data> | undefined {
 660     return this.workerNodes[workerNodeKey].tasksQueue.dequeue()
 661   }
 662
 663   private tasksQueueSize (workerNodeKey: number): number {
 664     return this.workerNodes[workerNodeKey].tasksQueue.size
 665   }
 666
 667   private flushTasksQueue (workerNodeKey: number): void {
 668     if (this.tasksQueueSize(workerNodeKey) > 0) {
 669       for (let i = 0; i < this.tasksQueueSize(workerNodeKey); i++) {
 670         this.executeTask(
 671           workerNodeKey,
 672           this.dequeueTask(workerNodeKey) as Task<Data>
 673         )
 674       }
 675     }
 676   }
 677
 678   private flushTasksQueueByWorker (worker: Worker): void {
 679     const workerNodeKey = this.getWorkerNodeKey(worker)
 680     this.flushTasksQueue(workerNodeKey)
 681   }
 682
 683   private flushTasksQueues (): void {
 684     for (const [workerNodeKey] of this.workerNodes.entries()) {
 685       this.flushTasksQueue(workerNodeKey)
 686     }
 687   }
 688 }