src/pools/abstract-pool.ts

   1 import crypto from 'node:crypto'
   2 import type { MessageValue, PromiseResponseWrapper } from '../utility-types'
   3 import { EMPTY_FUNCTION } from '../utils'
   4 import { KillBehaviors, isKillBehavior } from '../worker/worker-options'
   5 import { PoolEvents, type PoolOptions } from './pool'
   6 import { PoolEmitter } from './pool'
   7 import type { IPoolInternal, TasksUsage, WorkerType } from './pool-internal'
   8 import { PoolType } from './pool-internal'
   9 import type { IPoolWorker } from './pool-worker'
  10 import {
  11   WorkerChoiceStrategies,
  12   type WorkerChoiceStrategy
  13 } from './selection-strategies/selection-strategies-types'
  14 import { WorkerChoiceStrategyContext } from './selection-strategies/worker-choice-strategy-context'
  15
  16 /**
  17  * Base class that implements some shared logic for all poolifier pools.
  18  *
  19  * @typeParam Worker - Type of worker which manages this pool.
  20  * @typeParam Data - Type of data sent to the worker. This can only be serializable data.
  21  * @typeParam Response - Type of response of execution. This can only be serializable data.
  22  */
  23 export abstract class AbstractPool<
  24   Worker extends IPoolWorker,
  25   Data = unknown,
  26   Response = unknown
  27 > implements IPoolInternal<Worker, Data, Response> {
  28   /** @inheritDoc */
  29   public readonly workers: Array<WorkerType<Worker>> = []
  30
  31   /** @inheritDoc */
  32   public readonly emitter?: PoolEmitter
  33
  34   /**
  35    * The promise response map.
  36    *
  37    * - `key`: The message id of each submitted task.
  38    * - `value`: An object that contains the worker, the promise resolve and reject callbacks.
  39    *
  40    * When we receive a message from the worker we get a map entry with the promise resolve/reject bound to the message.
  41    */
  42   protected promiseResponseMap: Map<
  43   string,
  44   PromiseResponseWrapper<Worker, Response>
  45   > = new Map<string, PromiseResponseWrapper<Worker, Response>>()
  46
  47   /**
  48    * Worker choice strategy context referencing a worker choice algorithm implementation.
  49    *
  50    * Default to a round robin algorithm.
  51    */
  52   protected workerChoiceStrategyContext: WorkerChoiceStrategyContext<
  53   Worker,
  54   Data,
  55   Response
  56   >
  57
  58   /**
  59    * Constructs a new poolifier pool.
  60    *
  61    * @param numberOfWorkers - Number of workers that this pool should manage.
  62    * @param filePath - Path to the worker-file.
  63    * @param opts - Options for the pool.
  64    */
  65   public constructor (
  66     public readonly numberOfWorkers: number,
  67     public readonly filePath: string,
  68     public readonly opts: PoolOptions<Worker>
  69   ) {
  70     if (!this.isMain()) {
  71       throw new Error('Cannot start a pool from a worker!')
  72     }
  73     this.checkNumberOfWorkers(this.numberOfWorkers)
  74     this.checkFilePath(this.filePath)
  75     this.checkPoolOptions(this.opts)
  76
  77     this.chooseWorker.bind(this)
  78     this.internalExecute.bind(this)
  79     this.checkAndEmitFull.bind(this)
  80     this.checkAndEmitBusy.bind(this)
  81     this.sendToWorker.bind(this)
  82
  83     this.setupHook()
  84
  85     for (let i = 1; i <= this.numberOfWorkers; i++) {
  86       this.createAndSetupWorker()
  87     }
  88
  89     if (this.opts.enableEvents === true) {
  90       this.emitter = new PoolEmitter()
  91     }
  92     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext<
  93     Worker,
  94     Data,
  95     Response
  96     >(this, this.opts.workerChoiceStrategy)
  97   }
  98
  99   private checkFilePath (filePath: string): void {
 100     if (
 101       filePath == null ||
 102       (typeof filePath === 'string' && filePath.trim().length === 0)
 103     ) {
 104       throw new Error('Please specify a file with a worker implementation')
 105     }
 106   }
 107
 108   private checkNumberOfWorkers (numberOfWorkers: number): void {
 109     if (numberOfWorkers == null) {
 110       throw new Error(
 111         'Cannot instantiate a pool without specifying the number of workers'
 112       )
 113     } else if (!Number.isSafeInteger(numberOfWorkers)) {
 114       throw new TypeError(
 115         'Cannot instantiate a pool with a non integer number of workers'
 116       )
 117     } else if (numberOfWorkers < 0) {
 118       throw new RangeError(
 119         'Cannot instantiate a pool with a negative number of workers'
 120       )
 121     } else if (this.type === PoolType.FIXED && numberOfWorkers === 0) {
 122       throw new Error('Cannot instantiate a fixed pool with no worker')
 123     }
 124   }
 125
 126   private checkPoolOptions (opts: PoolOptions<Worker>): void {
 127     this.opts.workerChoiceStrategy =
 128       opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
 129     this.checkValidWorkerChoiceStrategy(this.opts.workerChoiceStrategy)
 130     this.opts.enableEvents = opts.enableEvents ?? true
 131   }
 132
 133   private checkValidWorkerChoiceStrategy (
 134     workerChoiceStrategy: WorkerChoiceStrategy
 135   ): void {
 136     if (!Object.values(WorkerChoiceStrategies).includes(workerChoiceStrategy)) {
 137       throw new Error(
 138         `Invalid worker choice strategy '${workerChoiceStrategy}'`
 139       )
 140     }
 141   }
 142
 143   /** @inheritDoc */
 144   public abstract get type (): PoolType
 145
 146   /**
 147    * Number of tasks concurrently running in the pool.
 148    */
 149   private get numberOfRunningTasks (): number {
 150     return this.promiseResponseMap.size
 151   }
 152
 153   /**
 154    * Gets the given worker key.
 155    *
 156    * @param worker - The worker.
 157    * @returns The worker key if the worker is found in the pool, `-1` otherwise.
 158    */
 159   private getWorkerKey (worker: Worker): number {
 160     return this.workers.findIndex(workerItem => workerItem.worker === worker)
 161   }
 162
 163   /** @inheritDoc */
 164   public setWorkerChoiceStrategy (
 165     workerChoiceStrategy: WorkerChoiceStrategy
 166   ): void {
 167     this.checkValidWorkerChoiceStrategy(workerChoiceStrategy)
 168     this.opts.workerChoiceStrategy = workerChoiceStrategy
 169     for (const [index, workerItem] of this.workers.entries()) {
 170       this.setWorker(index, workerItem.worker, {
 171         run: 0,
 172         running: 0,
 173         runTime: 0,
 174         avgRunTime: 0,
 175         error: 0
 176       })
 177     }
 178     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 179       workerChoiceStrategy
 180     )
 181   }
 182
 183   /** @inheritDoc */
 184   public abstract get full (): boolean
 185
 186   /** @inheritDoc */
 187   public abstract get busy (): boolean
 188
 189   protected internalBusy (): boolean {
 190     return (
 191       this.numberOfRunningTasks >= this.numberOfWorkers &&
 192       this.findFreeWorkerKey() === -1
 193     )
 194   }
 195
 196   /** @inheritDoc */
 197   public findFreeWorkerKey (): number {
 198     return this.workers.findIndex(workerItem => {
 199       return workerItem.tasksUsage.running === 0
 200     })
 201   }
 202
 203   /** @inheritDoc */
 204   public async execute (data: Data): Promise<Response> {
 205     const [workerKey, worker] = this.chooseWorker()
 206     const messageId = crypto.randomUUID()
 207     const res = this.internalExecute(workerKey, worker, messageId)
 208     this.checkAndEmitFull()
 209     this.checkAndEmitBusy()
 210     this.sendToWorker(worker, {
 211       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 212       data: data ?? ({} as Data),
 213       id: messageId
 214     })
 215     // eslint-disable-next-line @typescript-eslint/return-await
 216     return res
 217   }
 218
 219   /** @inheritDoc */
 220   public async destroy (): Promise<void> {
 221     await Promise.all(
 222       this.workers.map(async workerItem => {
 223         await this.destroyWorker(workerItem.worker)
 224       })
 225     )
 226   }
 227
 228   /**
 229    * Shutdowns given worker in the pool.
 230    *
 231    * @param worker - A worker within `workers`.
 232    */
 233   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 234
 235   /**
 236    * Setup hook that can be overridden by a Poolifier pool implementation
 237    * to run code before workers are created in the abstract constructor.
 238    * Can be overridden
 239    *
 240    * @virtual
 241    */
 242   protected setupHook (): void {
 243     // Intentionally empty
 244   }
 245
 246   /**
 247    * Should return whether the worker is the main worker or not.
 248    */
 249   protected abstract isMain (): boolean
 250
 251   /**
 252    * Hook executed before the worker task promise resolution.
 253    * Can be overridden.
 254    *
 255    * @param workerKey - The worker key.
 256    */
 257   protected beforePromiseResponseHook (workerKey: number): void {
 258     ++this.workers[workerKey].tasksUsage.running
 259   }
 260
 261   /**
 262    * Hook executed after the worker task promise resolution.
 263    * Can be overridden.
 264    *
 265    * @param worker - The worker.
 266    * @param message - The received message.
 267    */
 268   protected afterPromiseResponseHook (
 269     worker: Worker,
 270     message: MessageValue<Response>
 271   ): void {
 272     const workerTasksUsage = this.getWorkerTasksUsage(worker) as TasksUsage
 273     --workerTasksUsage.running
 274     ++workerTasksUsage.run
 275     if (message.error != null) {
 276       ++workerTasksUsage.error
 277     }
 278     if (this.workerChoiceStrategyContext.getRequiredStatistics().runTime) {
 279       workerTasksUsage.runTime += message.runTime ?? 0
 280       if (
 281         this.workerChoiceStrategyContext.getRequiredStatistics().avgRunTime &&
 282         workerTasksUsage.run !== 0
 283       ) {
 284         workerTasksUsage.avgRunTime =
 285           workerTasksUsage.runTime / workerTasksUsage.run
 286       }
 287     }
 288   }
 289
 290   /**
 291    * Chooses a worker for the next task.
 292    *
 293    * The default uses a round robin algorithm to distribute the load.
 294    *
 295    * @returns [worker key, worker].
 296    */
 297   protected chooseWorker (): [number, Worker] {
 298     let workerKey: number
 299     if (
 300       this.type === PoolType.DYNAMIC &&
 301       !this.full &&
 302       this.findFreeWorkerKey() === -1
 303     ) {
 304       const createdWorker = this.createAndSetupWorker()
 305       this.registerWorkerMessageListener(createdWorker, message => {
 306         if (
 307           isKillBehavior(KillBehaviors.HARD, message.kill) ||
 308           (message.kill != null &&
 309             this.getWorkerTasksUsage(createdWorker)?.running === 0)
 310         ) {
 311           // Kill message received from the worker, means that no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 312           void this.destroyWorker(createdWorker)
 313         }
 314       })
 315       workerKey = this.getWorkerKey(createdWorker)
 316     } else {
 317       workerKey = this.workerChoiceStrategyContext.execute()
 318     }
 319     return [workerKey, this.workers[workerKey].worker]
 320   }
 321
 322   /**
 323    * Sends a message to the given worker.
 324    *
 325    * @param worker - The worker which should receive the message.
 326    * @param message - The message.
 327    */
 328   protected abstract sendToWorker (
 329     worker: Worker,
 330     message: MessageValue<Data>
 331   ): void
 332
 333   /**
 334    * Registers a listener callback on a given worker.
 335    *
 336    * @param worker - The worker which should register a listener.
 337    * @param listener - The message listener callback.
 338    */
 339   protected abstract registerWorkerMessageListener<
 340     Message extends Data | Response
 341   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 342
 343   /**
 344    * Returns a newly created worker.
 345    */
 346   protected abstract createWorker (): Worker
 347
 348   /**
 349    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 350    *
 351    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 352    *
 353    * @param worker - The newly created worker.
 354    * @virtual
 355    */
 356   protected abstract afterWorkerSetup (worker: Worker): void
 357
 358   /**
 359    * Creates a new worker for this pool and sets it up completely.
 360    *
 361    * @returns New, completely set up worker.
 362    */
 363   protected createAndSetupWorker (): Worker {
 364     const worker = this.createWorker()
 365
 366     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 367     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 368     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 369     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 370     worker.once('exit', () => {
 371       this.removeWorker(worker)
 372     })
 373
 374     this.pushWorker(worker, {
 375       run: 0,
 376       running: 0,
 377       runTime: 0,
 378       avgRunTime: 0,
 379       error: 0
 380     })
 381
 382     this.afterWorkerSetup(worker)
 383
 384     return worker
 385   }
 386
 387   /**
 388    * This function is the listener registered for each worker.
 389    *
 390    * @returns The listener function to execute when a message is received from a worker.
 391    */
 392   protected workerListener (): (message: MessageValue<Response>) => void {
 393     return message => {
 394       if (message.id != null) {
 395         // Task response received
 396         const promiseResponse = this.promiseResponseMap.get(message.id)
 397         if (promiseResponse != null) {
 398           if (message.error != null) {
 399             promiseResponse.reject(message.error)
 400           } else {
 401             promiseResponse.resolve(message.data as Response)
 402           }
 403           this.afterPromiseResponseHook(promiseResponse.worker, message)
 404           this.promiseResponseMap.delete(message.id)
 405         }
 406       }
 407     }
 408   }
 409
 410   private async internalExecute (
 411     workerKey: number,
 412     worker: Worker,
 413     messageId: string
 414   ): Promise<Response> {
 415     this.beforePromiseResponseHook(workerKey)
 416     return await new Promise<Response>((resolve, reject) => {
 417       this.promiseResponseMap.set(messageId, { resolve, reject, worker })
 418     })
 419   }
 420
 421   private checkAndEmitBusy (): void {
 422     if (this.opts.enableEvents === true && this.busy) {
 423       this.emitter?.emit(PoolEvents.busy)
 424     }
 425   }
 426
 427   private checkAndEmitFull (): void {
 428     if (
 429       this.type === PoolType.DYNAMIC &&
 430       this.opts.enableEvents === true &&
 431       this.full
 432     ) {
 433       this.emitter?.emit(PoolEvents.full)
 434     }
 435   }
 436
 437   /**
 438    * Gets the given worker tasks usage in the pool.
 439    *
 440    * @param worker - The worker.
 441    * @returns The worker tasks usage.
 442    */
 443   private getWorkerTasksUsage (worker: Worker): TasksUsage | undefined {
 444     const workerKey = this.getWorkerKey(worker)
 445     if (workerKey !== -1) {
 446       return this.workers[workerKey].tasksUsage
 447     }
 448     throw new Error('Worker could not be found in the pool')
 449   }
 450
 451   /**
 452    * Pushes the given worker in the pool.
 453    *
 454    * @param worker - The worker.
 455    * @param tasksUsage - The worker tasks usage.
 456    */
 457   private pushWorker (worker: Worker, tasksUsage: TasksUsage): void {
 458     this.workers.push({
 459       worker,
 460       tasksUsage
 461     })
 462   }
 463
 464   /**
 465    * Sets the given worker in the pool.
 466    *
 467    * @param workerKey - The worker key.
 468    * @param worker - The worker.
 469    * @param tasksUsage - The worker tasks usage.
 470    */
 471   private setWorker (
 472     workerKey: number,
 473     worker: Worker,
 474     tasksUsage: TasksUsage
 475   ): void {
 476     this.workers[workerKey] = {
 477       worker,
 478       tasksUsage
 479     }
 480   }
 481
 482   /**
 483    * Removes the given worker from the pool.
 484    *
 485    * @param worker - The worker that will be removed.
 486    */
 487   protected removeWorker (worker: Worker): void {
 488     const workerKey = this.getWorkerKey(worker)
 489     this.workers.splice(workerKey, 1)
 490     this.workerChoiceStrategyContext.remove(workerKey)
 491   }
 492 }