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