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       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 this.findFreeWorkerNodeKey() === -1
 300   }
 301
 302   /** @inheritDoc */
 303   public findFreeWorkerNodeKey (): number {
 304     return this.workerNodes.findIndex(workerNode => {
 305       return workerNode.tasksUsage?.running === 0
 306     })
 307   }
 308
 309   /** @inheritDoc */
 310   public async execute (data?: Data): Promise<Response> {
 311     const [workerNodeKey, workerNode] = this.chooseWorkerNode()
 312     const submittedTask: Task<Data> = {
 313       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 314       data: data ?? ({} as Data),
 315       id: crypto.randomUUID()
 316     }
 317     const res = new Promise<Response>((resolve, reject) => {
 318       this.promiseResponseMap.set(submittedTask.id as string, {
 319         resolve,
 320         reject,
 321         worker: workerNode.worker
 322       })
 323     })
 324     if (
 325       this.opts.enableTasksQueue === true &&
 326       (this.busy ||
 327         this.workerNodes[workerNodeKey].tasksUsage.running >=
 328           ((this.opts.tasksQueueOptions as TasksQueueOptions)
 329             .concurrency as number))
 330     ) {
 331       this.enqueueTask(workerNodeKey, submittedTask)
 332     } else {
 333       this.executeTask(workerNodeKey, submittedTask)
 334     }
 335     this.checkAndEmitEvents()
 336     // eslint-disable-next-line @typescript-eslint/return-await
 337     return res
 338   }
 339
 340   /** @inheritDoc */
 341   public async destroy (): Promise<void> {
 342     await Promise.all(
 343       this.workerNodes.map(async (workerNode, workerNodeKey) => {
 344         this.flushTasksQueue(workerNodeKey)
 345         await this.destroyWorker(workerNode.worker)
 346       })
 347     )
 348   }
 349
 350   /**
 351    * Shutdowns the given worker.
 352    *
 353    * @param worker - A worker within `workerNodes`.
 354    */
 355   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 356
 357   /**
 358    * Setup hook to execute code before worker node are created in the abstract constructor.
 359    * Can be overridden
 360    *
 361    * @virtual
 362    */
 363   protected setupHook (): void {
 364     // Intentionally empty
 365   }
 366
 367   /**
 368    * Should return whether the worker is the main worker or not.
 369    */
 370   protected abstract isMain (): boolean
 371
 372   /**
 373    * Hook executed before the worker task execution.
 374    * Can be overridden.
 375    *
 376    * @param workerNodeKey - The worker node key.
 377    */
 378   protected beforeTaskExecutionHook (workerNodeKey: number): void {
 379     ++this.workerNodes[workerNodeKey].tasksUsage.running
 380   }
 381
 382   /**
 383    * Hook executed after the worker task execution.
 384    * Can be overridden.
 385    *
 386    * @param worker - The worker.
 387    * @param message - The received message.
 388    */
 389   protected afterTaskExecutionHook (
 390     worker: Worker,
 391     message: MessageValue<Response>
 392   ): void {
 393     const workerTasksUsage = this.getWorkerTasksUsage(worker) as TasksUsage
 394     --workerTasksUsage.running
 395     ++workerTasksUsage.run
 396     if (message.error != null) {
 397       ++workerTasksUsage.error
 398     }
 399     if (this.workerChoiceStrategyContext.getRequiredStatistics().runTime) {
 400       workerTasksUsage.runTime += message.runTime ?? 0
 401       if (
 402         this.workerChoiceStrategyContext.getRequiredStatistics().avgRunTime &&
 403         workerTasksUsage.run !== 0
 404       ) {
 405         workerTasksUsage.avgRunTime =
 406           workerTasksUsage.runTime / workerTasksUsage.run
 407       }
 408       if (this.workerChoiceStrategyContext.getRequiredStatistics().medRunTime) {
 409         workerTasksUsage.runTimeHistory.push(message.runTime ?? 0)
 410         workerTasksUsage.medRunTime = median(workerTasksUsage.runTimeHistory)
 411       }
 412     }
 413   }
 414
 415   /**
 416    * Chooses a worker node for the next task.
 417    *
 418    * The default uses a round robin algorithm to distribute the load.
 419    *
 420    * @returns [worker node key, worker node].
 421    */
 422   protected chooseWorkerNode (): [number, WorkerNode<Worker, Data>] {
 423     let workerNodeKey: number
 424     if (this.type === PoolType.DYNAMIC && !this.full && this.internalBusy()) {
 425       const workerCreated = this.createAndSetupWorker()
 426       this.registerWorkerMessageListener(workerCreated, message => {
 427         if (
 428           isKillBehavior(KillBehaviors.HARD, message.kill) ||
 429           (message.kill != null &&
 430             this.getWorkerTasksUsage(workerCreated)?.running === 0)
 431         ) {
 432           // Kill message received from the worker: no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 433           this.flushTasksQueueByWorker(workerCreated)
 434           void this.destroyWorker(workerCreated)
 435         }
 436       })
 437       workerNodeKey = this.getWorkerNodeKey(workerCreated)
 438     } else {
 439       workerNodeKey = this.workerChoiceStrategyContext.execute()
 440     }
 441     return [workerNodeKey, this.workerNodes[workerNodeKey]]
 442   }
 443
 444   /**
 445    * Sends a message to the given worker.
 446    *
 447    * @param worker - The worker which should receive the message.
 448    * @param message - The message.
 449    */
 450   protected abstract sendToWorker (
 451     worker: Worker,
 452     message: MessageValue<Data>
 453   ): void
 454
 455   /**
 456    * Registers a listener callback on the given worker.
 457    *
 458    * @param worker - The worker which should register a listener.
 459    * @param listener - The message listener callback.
 460    */
 461   protected abstract registerWorkerMessageListener<
 462     Message extends Data | Response
 463   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 464
 465   /**
 466    * Returns a newly created worker.
 467    */
 468   protected abstract createWorker (): Worker
 469
 470   /**
 471    * Function that can be hooked up when a worker has been newly created and moved to the pool worker nodes.
 472    *
 473    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 474    *
 475    * @param worker - The newly created worker.
 476    */
 477   protected abstract afterWorkerSetup (worker: Worker): void
 478
 479   /**
 480    * Creates a new worker and sets it up completely in the pool worker nodes.
 481    *
 482    * @returns New, completely set up worker.
 483    */
 484   protected createAndSetupWorker (): Worker {
 485     const worker = this.createWorker()
 486
 487     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 488     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 489     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 490     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 491     worker.once('exit', () => {
 492       this.removeWorkerNode(worker)
 493     })
 494
 495     this.pushWorkerNode(worker)
 496
 497     this.afterWorkerSetup(worker)
 498
 499     return worker
 500   }
 501
 502   /**
 503    * This function is the listener registered for each worker message.
 504    *
 505    * @returns The listener function to execute when a message is received from a worker.
 506    */
 507   protected workerListener (): (message: MessageValue<Response>) => void {
 508     return message => {
 509       if (message.id != null) {
 510         // Task execution response received
 511         const promiseResponse = this.promiseResponseMap.get(message.id)
 512         if (promiseResponse != null) {
 513           if (message.error != null) {
 514             promiseResponse.reject(message.error)
 515           } else {
 516             promiseResponse.resolve(message.data as Response)
 517           }
 518           this.afterTaskExecutionHook(promiseResponse.worker, message)
 519           this.promiseResponseMap.delete(message.id)
 520           const workerNodeKey = this.getWorkerNodeKey(promiseResponse.worker)
 521           if (
 522             this.opts.enableTasksQueue === true &&
 523             this.tasksQueueSize(workerNodeKey) > 0
 524           ) {
 525             this.executeTask(
 526               workerNodeKey,
 527               this.dequeueTask(workerNodeKey) as Task<Data>
 528             )
 529           }
 530         }
 531       }
 532     }
 533   }
 534
 535   private checkAndEmitEvents (): void {
 536     if (this.opts.enableEvents === true) {
 537       if (this.busy) {
 538         this.emitter?.emit(PoolEvents.busy)
 539       }
 540       if (this.type === PoolType.DYNAMIC && this.full) {
 541         this.emitter?.emit(PoolEvents.full)
 542       }
 543     }
 544   }
 545
 546   /**
 547    * Sets the given worker node its tasks usage in the pool.
 548    *
 549    * @param workerNode - The worker node.
 550    * @param tasksUsage - The worker node tasks usage.
 551    */
 552   private setWorkerNodeTasksUsage (
 553     workerNode: WorkerNode<Worker, Data>,
 554     tasksUsage: TasksUsage
 555   ): void {
 556     workerNode.tasksUsage = tasksUsage
 557   }
 558
 559   /**
 560    * Gets the given worker its tasks usage in the pool.
 561    *
 562    * @param worker - The worker.
 563    * @throws Error if the worker is not found in the pool worker nodes.
 564    * @returns The worker tasks usage.
 565    */
 566   private getWorkerTasksUsage (worker: Worker): TasksUsage | undefined {
 567     const workerNodeKey = this.getWorkerNodeKey(worker)
 568     if (workerNodeKey !== -1) {
 569       return this.workerNodes[workerNodeKey].tasksUsage
 570     }
 571     throw new Error('Worker could not be found in the pool worker nodes')
 572   }
 573
 574   /**
 575    * Pushes the given worker in the pool worker nodes.
 576    *
 577    * @param worker - The worker.
 578    * @returns The worker nodes length.
 579    */
 580   private pushWorkerNode (worker: Worker): number {
 581     return this.workerNodes.push({
 582       worker,
 583       tasksUsage: {
 584         run: 0,
 585         running: 0,
 586         runTime: 0,
 587         runTimeHistory: new CircularArray(),
 588         avgRunTime: 0,
 589         medRunTime: 0,
 590         error: 0
 591       },
 592       tasksQueue: []
 593     })
 594   }
 595
 596   /**
 597    * Sets the given worker in the pool worker nodes.
 598    *
 599    * @param workerNodeKey - The worker node key.
 600    * @param worker - The worker.
 601    * @param tasksUsage - The worker tasks usage.
 602    * @param tasksQueue - The worker task queue.
 603    */
 604   private setWorkerNode (
 605     workerNodeKey: number,
 606     worker: Worker,
 607     tasksUsage: TasksUsage,
 608     tasksQueue: Array<Task<Data>>
 609   ): void {
 610     this.workerNodes[workerNodeKey] = {
 611       worker,
 612       tasksUsage,
 613       tasksQueue
 614     }
 615   }
 616
 617   /**
 618    * Removes the given worker from the pool worker nodes.
 619    *
 620    * @param worker - The worker.
 621    */
 622   private removeWorkerNode (worker: Worker): void {
 623     const workerNodeKey = this.getWorkerNodeKey(worker)
 624     this.workerNodes.splice(workerNodeKey, 1)
 625     this.workerChoiceStrategyContext.remove(workerNodeKey)
 626   }
 627
 628   private executeTask (workerNodeKey: number, task: Task<Data>): void {
 629     this.beforeTaskExecutionHook(workerNodeKey)
 630     this.sendToWorker(this.workerNodes[workerNodeKey].worker, task)
 631   }
 632
 633   private enqueueTask (workerNodeKey: number, task: Task<Data>): number {
 634     return this.workerNodes[workerNodeKey].tasksQueue.push(task)
 635   }
 636
 637   private dequeueTask (workerNodeKey: number): Task<Data> | undefined {
 638     return this.workerNodes[workerNodeKey].tasksQueue.shift()
 639   }
 640
 641   private tasksQueueSize (workerNodeKey: number): number {
 642     return this.workerNodes[workerNodeKey].tasksQueue.length
 643   }
 644
 645   private flushTasksQueue (workerNodeKey: number): void {
 646     if (this.tasksQueueSize(workerNodeKey) > 0) {
 647       for (const task of this.workerNodes[workerNodeKey].tasksQueue) {
 648         this.executeTask(workerNodeKey, task)
 649       }
 650     }
 651   }
 652
 653   private flushTasksQueueByWorker (worker: Worker): void {
 654     const workerNodeKey = this.getWorkerNodeKey(worker)
 655     this.flushTasksQueue(workerNodeKey)
 656   }
 657
 658   private flushTasksQueues (): void {
 659     for (const [workerNodeKey] of this.workerNodes.entries()) {
 660       this.flushTasksQueue(workerNodeKey)
 661     }
 662   }
 663 }