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