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 { CircularArray } from '../circular-array'
  10 import {
  11   type IPool,
  12   PoolEmitter,
  13   PoolEvents,
  14   type PoolOptions,
  15   PoolType,
  16   type TasksQueueOptions
  17 } from './pool'
  18 import type { IWorker, Task, TasksUsage, WorkerNode } from './worker'
  19 import {
  20   WorkerChoiceStrategies,
  21   type WorkerChoiceStrategy,
  22   type WorkerChoiceStrategyOptions
  23 } from './selection-strategies/selection-strategies-types'
  24 import { WorkerChoiceStrategyContext } from './selection-strategies/worker-choice-strategy-context'
  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 = this.chooseWorkerNode.bind(this)
  88     this.executeTask = this.executeTask.bind(this)
  89     this.enqueueTask = this.enqueueTask.bind(this)
  90     this.checkAndEmitEvents = 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     workerChoiceStrategyOptions?: WorkerChoiceStrategyOptions
 221   ): void {
 222     this.checkValidWorkerChoiceStrategy(workerChoiceStrategy)
 223     this.opts.workerChoiceStrategy = workerChoiceStrategy
 224     for (const workerNode of this.workerNodes) {
 225       this.setWorkerNodeTasksUsage(workerNode, {
 226         run: 0,
 227         running: 0,
 228         runTime: 0,
 229         runTimeHistory: new CircularArray(),
 230         avgRunTime: 0,
 231         medRunTime: 0,
 232         error: 0
 233       })
 234     }
 235     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 236       this.opts.workerChoiceStrategy
 237     )
 238     if (workerChoiceStrategyOptions != null) {
 239       this.setWorkerChoiceStrategyOptions(workerChoiceStrategyOptions)
 240     }
 241   }
 242
 243   /** @inheritDoc */
 244   public setWorkerChoiceStrategyOptions (
 245     workerChoiceStrategyOptions: WorkerChoiceStrategyOptions
 246   ): void {
 247     this.opts.workerChoiceStrategyOptions = workerChoiceStrategyOptions
 248     this.workerChoiceStrategyContext.setOptions(
 249       this.opts.workerChoiceStrategyOptions
 250     )
 251   }
 252
 253   /** @inheritDoc */
 254   public enableTasksQueue (
 255     enable: boolean,
 256     tasksQueueOptions?: TasksQueueOptions
 257   ): void {
 258     if (this.opts.enableTasksQueue === true && !enable) {
 259       this.flushTasksQueues()
 260     }
 261     this.opts.enableTasksQueue = enable
 262     this.setTasksQueueOptions(tasksQueueOptions as TasksQueueOptions)
 263   }
 264
 265   /** @inheritDoc */
 266   public setTasksQueueOptions (tasksQueueOptions: TasksQueueOptions): void {
 267     if (this.opts.enableTasksQueue === true) {
 268       this.checkValidTasksQueueOptions(tasksQueueOptions)
 269       this.opts.tasksQueueOptions =
 270         this.buildTasksQueueOptions(tasksQueueOptions)
 271     } else {
 272       delete this.opts.tasksQueueOptions
 273     }
 274   }
 275
 276   private buildTasksQueueOptions (
 277     tasksQueueOptions: TasksQueueOptions
 278   ): TasksQueueOptions {
 279     return {
 280       concurrency: tasksQueueOptions?.concurrency ?? 1
 281     }
 282   }
 283
 284   /**
 285    * Whether the pool is full or not.
 286    *
 287    * The pool filling boolean status.
 288    */
 289   protected abstract get full (): boolean
 290
 291   /**
 292    * Whether the pool is busy or not.
 293    *
 294    * The pool busyness boolean status.
 295    */
 296   protected abstract get busy (): boolean
 297
 298   protected internalBusy (): boolean {
 299     return (
 300       this.workerNodes.findIndex(workerNode => {
 301         return workerNode.tasksUsage?.running === 0
 302       }) === -1
 303     )
 304   }
 305
 306   /** @inheritDoc */
 307   public async execute (data?: Data, name?: string): Promise<Response> {
 308     const [workerNodeKey, workerNode] = this.chooseWorkerNode()
 309     const submittedTask: Task<Data> = {
 310       name,
 311       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 312       data: data ?? ({} as Data),
 313       id: crypto.randomUUID()
 314     }
 315     const res = new Promise<Response>((resolve, reject) => {
 316       this.promiseResponseMap.set(submittedTask.id as string, {
 317         resolve,
 318         reject,
 319         worker: workerNode.worker
 320       })
 321     })
 322     if (
 323       this.opts.enableTasksQueue === true &&
 324       (this.busy ||
 325         this.workerNodes[workerNodeKey].tasksUsage.running >=
 326           ((this.opts.tasksQueueOptions as TasksQueueOptions)
 327             .concurrency as number))
 328     ) {
 329       this.enqueueTask(workerNodeKey, submittedTask)
 330     } else {
 331       this.executeTask(workerNodeKey, submittedTask)
 332     }
 333     this.checkAndEmitEvents()
 334     // eslint-disable-next-line @typescript-eslint/return-await
 335     return res
 336   }
 337
 338   /** @inheritDoc */
 339   public async destroy (): Promise<void> {
 340     await Promise.all(
 341       this.workerNodes.map(async (workerNode, workerNodeKey) => {
 342         this.flushTasksQueue(workerNodeKey)
 343         await this.destroyWorker(workerNode.worker)
 344       })
 345     )
 346   }
 347
 348   /**
 349    * Shutdowns the given worker.
 350    *
 351    * @param worker - A worker within `workerNodes`.
 352    */
 353   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 354
 355   /**
 356    * Setup hook to execute code before worker node are created in the abstract constructor.
 357    * Can be overridden
 358    *
 359    * @virtual
 360    */
 361   protected setupHook (): void {
 362     // Intentionally empty
 363   }
 364
 365   /**
 366    * Should return whether the worker is the main worker or not.
 367    */
 368   protected abstract isMain (): boolean
 369
 370   /**
 371    * Hook executed before the worker task execution.
 372    * Can be overridden.
 373    *
 374    * @param workerNodeKey - The worker node key.
 375    */
 376   protected beforeTaskExecutionHook (workerNodeKey: number): void {
 377     ++this.workerNodes[workerNodeKey].tasksUsage.running
 378   }
 379
 380   /**
 381    * Hook executed after the worker task execution.
 382    * Can be overridden.
 383    *
 384    * @param worker - The worker.
 385    * @param message - The received message.
 386    */
 387   protected afterTaskExecutionHook (
 388     worker: Worker,
 389     message: MessageValue<Response>
 390   ): void {
 391     const workerTasksUsage = this.getWorkerTasksUsage(worker)
 392     --workerTasksUsage.running
 393     ++workerTasksUsage.run
 394     if (message.error != null) {
 395       ++workerTasksUsage.error
 396     }
 397     if (this.workerChoiceStrategyContext.getRequiredStatistics().runTime) {
 398       workerTasksUsage.runTime += message.runTime ?? 0
 399       if (
 400         this.workerChoiceStrategyContext.getRequiredStatistics().avgRunTime &&
 401         workerTasksUsage.run !== 0
 402       ) {
 403         workerTasksUsage.avgRunTime =
 404           workerTasksUsage.runTime / workerTasksUsage.run
 405       }
 406       if (this.workerChoiceStrategyContext.getRequiredStatistics().medRunTime) {
 407         workerTasksUsage.runTimeHistory.push(message.runTime ?? 0)
 408         workerTasksUsage.medRunTime = median(workerTasksUsage.runTimeHistory)
 409       }
 410     }
 411   }
 412
 413   /**
 414    * Chooses a worker node for the next task.
 415    *
 416    * The default uses a round robin algorithm to distribute the load.
 417    *
 418    * @returns [worker node key, worker node].
 419    */
 420   protected chooseWorkerNode (): [number, WorkerNode<Worker, Data>] {
 421     let workerNodeKey: number
 422     if (this.type === PoolType.DYNAMIC && !this.full && this.internalBusy()) {
 423       const workerCreated = this.createAndSetupWorker()
 424       this.registerWorkerMessageListener(workerCreated, message => {
 425         if (
 426           isKillBehavior(KillBehaviors.HARD, message.kill) ||
 427           (message.kill != null &&
 428             this.getWorkerTasksUsage(workerCreated)?.running === 0)
 429         ) {
 430           // Kill message received from the worker: no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 431           this.flushTasksQueueByWorker(workerCreated)
 432           void (this.destroyWorker(workerCreated) as Promise<void>)
 433         }
 434       })
 435       workerNodeKey = this.getWorkerNodeKey(workerCreated)
 436     } else {
 437       workerNodeKey = this.workerChoiceStrategyContext.execute()
 438     }
 439     return [workerNodeKey, this.workerNodes[workerNodeKey]]
 440   }
 441
 442   /**
 443    * Sends a message to the given worker.
 444    *
 445    * @param worker - The worker which should receive the message.
 446    * @param message - The message.
 447    */
 448   protected abstract sendToWorker (
 449     worker: Worker,
 450     message: MessageValue<Data>
 451   ): void
 452
 453   /**
 454    * Registers a listener callback on the given worker.
 455    *
 456    * @param worker - The worker which should register a listener.
 457    * @param listener - The message listener callback.
 458    */
 459   protected abstract registerWorkerMessageListener<
 460     Message extends Data | Response
 461   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 462
 463   /**
 464    * Returns a newly created worker.
 465    */
 466   protected abstract createWorker (): Worker
 467
 468   /**
 469    * Function that can be hooked up when a worker has been newly created and moved to the pool worker nodes.
 470    *
 471    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 472    *
 473    * @param worker - The newly created worker.
 474    */
 475   protected abstract afterWorkerSetup (worker: Worker): void
 476
 477   /**
 478    * Creates a new worker and sets it up completely in the pool worker nodes.
 479    *
 480    * @returns New, completely set up worker.
 481    */
 482   protected createAndSetupWorker (): Worker {
 483     const worker = this.createWorker()
 484
 485     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 486     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 487     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 488     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 489     worker.once('exit', () => {
 490       this.removeWorkerNode(worker)
 491     })
 492
 493     this.pushWorkerNode(worker)
 494
 495     this.afterWorkerSetup(worker)
 496
 497     return worker
 498   }
 499
 500   /**
 501    * This function is the listener registered for each worker message.
 502    *
 503    * @returns The listener function to execute when a message is received from a worker.
 504    */
 505   protected workerListener (): (message: MessageValue<Response>) => void {
 506     return message => {
 507       if (message.id != null) {
 508         // Task execution response received
 509         const promiseResponse = this.promiseResponseMap.get(message.id)
 510         if (promiseResponse != null) {
 511           if (message.error != null) {
 512             promiseResponse.reject(message.error)
 513           } else {
 514             promiseResponse.resolve(message.data as Response)
 515           }
 516           this.afterTaskExecutionHook(promiseResponse.worker, message)
 517           this.promiseResponseMap.delete(message.id)
 518           const workerNodeKey = this.getWorkerNodeKey(promiseResponse.worker)
 519           if (
 520             this.opts.enableTasksQueue === true &&
 521             this.tasksQueueSize(workerNodeKey) > 0
 522           ) {
 523             this.executeTask(
 524               workerNodeKey,
 525               this.dequeueTask(workerNodeKey) as Task<Data>
 526             )
 527           }
 528         }
 529       }
 530     }
 531   }
 532
 533   private checkAndEmitEvents (): void {
 534     if (this.opts.enableEvents === true) {
 535       if (this.busy) {
 536         this.emitter?.emit(PoolEvents.busy)
 537       }
 538       if (this.type === PoolType.DYNAMIC && this.full) {
 539         this.emitter?.emit(PoolEvents.full)
 540       }
 541     }
 542   }
 543
 544   /**
 545    * Sets the given worker node its tasks usage in the pool.
 546    *
 547    * @param workerNode - The worker node.
 548    * @param tasksUsage - The worker node tasks usage.
 549    */
 550   private setWorkerNodeTasksUsage (
 551     workerNode: WorkerNode<Worker, Data>,
 552     tasksUsage: TasksUsage
 553   ): void {
 554     workerNode.tasksUsage = tasksUsage
 555   }
 556
 557   /**
 558    * Gets the given worker its tasks usage in the pool.
 559    *
 560    * @param worker - The worker.
 561    * @throws Error if the worker is not found in the pool worker nodes.
 562    * @returns The worker tasks usage.
 563    */
 564   private getWorkerTasksUsage (worker: Worker): TasksUsage {
 565     const workerNodeKey = this.getWorkerNodeKey(worker)
 566     if (workerNodeKey !== -1) {
 567       return this.workerNodes[workerNodeKey].tasksUsage
 568     }
 569     throw new Error('Worker could not be found in the pool worker nodes')
 570   }
 571
 572   /**
 573    * Pushes the given worker in the pool worker nodes.
 574    *
 575    * @param worker - The worker.
 576    * @returns The worker nodes length.
 577    */
 578   private pushWorkerNode (worker: Worker): number {
 579     return this.workerNodes.push({
 580       worker,
 581       tasksUsage: {
 582         run: 0,
 583         running: 0,
 584         runTime: 0,
 585         runTimeHistory: new CircularArray(),
 586         avgRunTime: 0,
 587         medRunTime: 0,
 588         error: 0
 589       },
 590       tasksQueue: []
 591     })
 592   }
 593
 594   /**
 595    * Sets the given worker in the pool worker nodes.
 596    *
 597    * @param workerNodeKey - The worker node key.
 598    * @param worker - The worker.
 599    * @param tasksUsage - The worker tasks usage.
 600    * @param tasksQueue - The worker task queue.
 601    */
 602   private setWorkerNode (
 603     workerNodeKey: number,
 604     worker: Worker,
 605     tasksUsage: TasksUsage,
 606     tasksQueue: Array<Task<Data>>
 607   ): void {
 608     this.workerNodes[workerNodeKey] = {
 609       worker,
 610       tasksUsage,
 611       tasksQueue
 612     }
 613   }
 614
 615   /**
 616    * Removes the given worker from the pool worker nodes.
 617    *
 618    * @param worker - The worker.
 619    */
 620   private removeWorkerNode (worker: Worker): void {
 621     const workerNodeKey = this.getWorkerNodeKey(worker)
 622     this.workerNodes.splice(workerNodeKey, 1)
 623     this.workerChoiceStrategyContext.remove(workerNodeKey)
 624   }
 625
 626   private executeTask (workerNodeKey: number, task: Task<Data>): void {
 627     this.beforeTaskExecutionHook(workerNodeKey)
 628     this.sendToWorker(this.workerNodes[workerNodeKey].worker, task)
 629   }
 630
 631   private enqueueTask (workerNodeKey: number, task: Task<Data>): number {
 632     return this.workerNodes[workerNodeKey].tasksQueue.push(task)
 633   }
 634
 635   private dequeueTask (workerNodeKey: number): Task<Data> | undefined {
 636     return this.workerNodes[workerNodeKey].tasksQueue.shift()
 637   }
 638
 639   private tasksQueueSize (workerNodeKey: number): number {
 640     return this.workerNodes[workerNodeKey].tasksQueue.length
 641   }
 642
 643   private flushTasksQueue (workerNodeKey: number): void {
 644     if (this.tasksQueueSize(workerNodeKey) > 0) {
 645       for (const task of this.workerNodes[workerNodeKey].tasksQueue) {
 646         this.executeTask(workerNodeKey, task)
 647       }
 648     }
 649   }
 650
 651   private flushTasksQueueByWorker (worker: Worker): void {
 652     const workerNodeKey = this.getWorkerNodeKey(worker)
 653     this.flushTasksQueue(workerNodeKey)
 654   }
 655
 656   private flushTasksQueues (): void {
 657     for (const [workerNodeKey] of this.workerNodes.entries()) {
 658       this.flushTasksQueue(workerNodeKey)
 659     }
 660   }
 661 }