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 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 instance implementing the worker choice algorithm.
  49    *
  50    * Default to a strategy implementing 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.checkAndEmitBusy.bind(this)
  80     this.sendToWorker.bind(this)
  81
  82     this.setupHook()
  83
  84     for (let i = 1; i <= this.numberOfWorkers; i++) {
  85       this.createAndSetupWorker()
  86     }
  87
  88     if (this.opts.enableEvents === true) {
  89       this.emitter = new PoolEmitter()
  90     }
  91     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext<
  92     Worker,
  93     Data,
  94     Response
  95     >(
  96       this,
  97       () => {
  98         const createdWorker = this.createAndSetupWorker()
  99         this.registerWorkerMessageListener(createdWorker, message => {
 100           if (
 101             isKillBehavior(KillBehaviors.HARD, message.kill) ||
 102             this.getWorkerTasksUsage(createdWorker)?.running === 0
 103           ) {
 104             // Kill received from the worker, means that no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 105             void this.destroyWorker(createdWorker)
 106           }
 107         })
 108         return this.getWorkerKey(createdWorker)
 109       },
 110       this.opts.workerChoiceStrategy
 111     )
 112   }
 113
 114   private checkFilePath (filePath: string): void {
 115     if (
 116       filePath == null ||
 117       (typeof filePath === 'string' && filePath.trim().length === 0)
 118     ) {
 119       throw new Error('Please specify a file with a worker implementation')
 120     }
 121   }
 122
 123   private checkNumberOfWorkers (numberOfWorkers: number): void {
 124     if (numberOfWorkers == null) {
 125       throw new Error(
 126         'Cannot instantiate a pool without specifying the number of workers'
 127       )
 128     } else if (!Number.isSafeInteger(numberOfWorkers)) {
 129       throw new TypeError(
 130         'Cannot instantiate a pool with a non integer number of workers'
 131       )
 132     } else if (numberOfWorkers < 0) {
 133       throw new RangeError(
 134         'Cannot instantiate a pool with a negative number of workers'
 135       )
 136     } else if (this.type === PoolType.FIXED && numberOfWorkers === 0) {
 137       throw new Error('Cannot instantiate a fixed pool with no worker')
 138     }
 139   }
 140
 141   private checkPoolOptions (opts: PoolOptions<Worker>): void {
 142     this.opts.workerChoiceStrategy =
 143       opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
 144     this.opts.enableEvents = opts.enableEvents ?? true
 145   }
 146
 147   /** {@inheritDoc} */
 148   public abstract get type (): PoolType
 149
 150   /**
 151    * Number of tasks concurrently running.
 152    */
 153   private get numberOfRunningTasks (): number {
 154     return this.promiseResponseMap.size
 155   }
 156
 157   /**
 158    * Gets the given worker key.
 159    *
 160    * @param worker - The worker.
 161    * @returns The worker key if the worker is found in the pool, `-1` otherwise.
 162    */
 163   private getWorkerKey (worker: Worker): number {
 164     return this.workers.findIndex(workerItem => workerItem.worker === worker)
 165   }
 166
 167   /** {@inheritDoc} */
 168   public setWorkerChoiceStrategy (
 169     workerChoiceStrategy: WorkerChoiceStrategy
 170   ): void {
 171     this.opts.workerChoiceStrategy = workerChoiceStrategy
 172     for (const [index, workerItem] of this.workers.entries()) {
 173       this.setWorker(index, workerItem.worker, {
 174         run: 0,
 175         running: 0,
 176         runTime: 0,
 177         avgRunTime: 0,
 178         error: 0
 179       })
 180     }
 181     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 182       this,
 183       workerChoiceStrategy
 184     )
 185   }
 186
 187   /** {@inheritDoc} */
 188   public abstract get full (): boolean
 189
 190   /** {@inheritDoc} */
 191   public abstract get busy (): boolean
 192
 193   protected internalBusy (): boolean {
 194     return (
 195       this.numberOfRunningTasks >= this.numberOfWorkers &&
 196       this.findFreeWorkerKey() === -1
 197     )
 198   }
 199
 200   /** {@inheritDoc} */
 201   public findFreeWorkerKey (): number {
 202     return this.workers.findIndex(workerItem => {
 203       return workerItem.tasksUsage.running === 0
 204     })
 205   }
 206
 207   /** {@inheritDoc} */
 208   public async execute (data: Data): Promise<Response> {
 209     const [workerKey, worker] = this.chooseWorker()
 210     const messageId = crypto.randomUUID()
 211     const res = this.internalExecute(workerKey, worker, messageId)
 212     this.checkAndEmitBusy()
 213     this.sendToWorker(worker, {
 214       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 215       data: data ?? ({} as Data),
 216       id: messageId
 217     })
 218     // eslint-disable-next-line @typescript-eslint/return-await
 219     return res
 220   }
 221
 222   /** {@inheritDoc} */
 223   public async destroy (): Promise<void> {
 224     await Promise.all(
 225       this.workers.map(async workerItem => {
 226         await this.destroyWorker(workerItem.worker)
 227       })
 228     )
 229   }
 230
 231   /**
 232    * Shutdowns given worker.
 233    *
 234    * @param worker - A worker within `workers`.
 235    */
 236   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 237
 238   /**
 239    * Setup hook that can be overridden by a Poolifier pool implementation
 240    * to run code before workers are created in the abstract constructor.
 241    */
 242   protected setupHook (): void {
 243     // Can be overridden
 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.taskRunTime ?? 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    * Removes the given worker from the pool.
 292    *
 293    * @param worker - The worker that will be removed.
 294    */
 295   protected removeWorker (worker: Worker): void {
 296     const workerKey = this.getWorkerKey(worker)
 297     this.workers.splice(workerKey, 1)
 298     this.workerChoiceStrategyContext.remove(workerKey)
 299   }
 300
 301   /**
 302    * Chooses a worker for the next task.
 303    *
 304    * The default implementation uses a round robin algorithm to distribute the load.
 305    *
 306    * @returns [worker key, worker].
 307    */
 308   protected chooseWorker (): [number, Worker] {
 309     const workerKey = this.workerChoiceStrategyContext.execute()
 310     return [workerKey, this.workers[workerKey].worker]
 311   }
 312
 313   /**
 314    * Sends a message to the given worker.
 315    *
 316    * @param worker - The worker which should receive the message.
 317    * @param message - The message.
 318    */
 319   protected abstract sendToWorker (
 320     worker: Worker,
 321     message: MessageValue<Data>
 322   ): void
 323
 324   /**
 325    * Registers a listener callback on a given worker.
 326    *
 327    * @param worker - The worker which should register a listener.
 328    * @param listener - The message listener callback.
 329    */
 330   protected abstract registerWorkerMessageListener<
 331     Message extends Data | Response
 332   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 333
 334   /**
 335    * Returns a newly created worker.
 336    */
 337   protected abstract createWorker (): Worker
 338
 339   /**
 340    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 341    *
 342    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 343    *
 344    * @param worker - The newly created worker.
 345    */
 346   protected abstract afterWorkerSetup (worker: Worker): void
 347
 348   /**
 349    * Creates a new worker for this pool and sets it up completely.
 350    *
 351    * @returns New, completely set up worker.
 352    */
 353   protected createAndSetupWorker (): Worker {
 354     const worker = this.createWorker()
 355
 356     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 357     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 358     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 359     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 360     worker.once('exit', () => {
 361       this.removeWorker(worker)
 362     })
 363
 364     this.pushWorker(worker, {
 365       run: 0,
 366       running: 0,
 367       runTime: 0,
 368       avgRunTime: 0,
 369       error: 0
 370     })
 371
 372     this.afterWorkerSetup(worker)
 373
 374     return worker
 375   }
 376
 377   /**
 378    * This function is the listener registered for each worker.
 379    *
 380    * @returns The listener function to execute when a message is received from a worker.
 381    */
 382   protected workerListener (): (message: MessageValue<Response>) => void {
 383     return message => {
 384       if (message.id !== undefined) {
 385         const promiseResponse = this.promiseResponseMap.get(message.id)
 386         if (promiseResponse !== undefined) {
 387           if (message.error != null) {
 388             promiseResponse.reject(message.error)
 389           } else {
 390             promiseResponse.resolve(message.data as Response)
 391           }
 392           this.afterPromiseResponseHook(promiseResponse.worker, message)
 393           this.promiseResponseMap.delete(message.id)
 394         }
 395       }
 396     }
 397   }
 398
 399   private async internalExecute (
 400     workerKey: number,
 401     worker: Worker,
 402     messageId: string
 403   ): Promise<Response> {
 404     this.beforePromiseResponseHook(workerKey)
 405     return await new Promise<Response>((resolve, reject) => {
 406       this.promiseResponseMap.set(messageId, { resolve, reject, worker })
 407     })
 408   }
 409
 410   private checkAndEmitBusy (): void {
 411     if (this.opts.enableEvents === true && this.busy) {
 412       this.emitter?.emit('busy')
 413     }
 414   }
 415
 416   /**
 417    * Gets worker tasks usage.
 418    *
 419    * @param worker - The worker.
 420    * @returns The worker tasks usage.
 421    */
 422   private getWorkerTasksUsage (worker: Worker): TasksUsage | undefined {
 423     const workerKey = this.getWorkerKey(worker)
 424     if (workerKey !== -1) {
 425       return this.workers[workerKey].tasksUsage
 426     }
 427     throw new Error('Worker could not be found in the pool')
 428   }
 429
 430   /**
 431    * Pushes the given worker.
 432    *
 433    * @param worker - The worker.
 434    * @param tasksUsage - The worker tasks usage.
 435    */
 436   private pushWorker (worker: Worker, tasksUsage: TasksUsage): void {
 437     this.workers.push({
 438       worker,
 439       tasksUsage
 440     })
 441   }
 442
 443   /**
 444    * Sets the given worker.
 445    *
 446    * @param workerKey - The worker key.
 447    * @param worker - The worker.
 448    * @param tasksUsage - The worker tasks usage.
 449    */
 450   private setWorker (
 451     workerKey: number,
 452     worker: Worker,
 453     tasksUsage: TasksUsage
 454   ): void {
 455     this.workers[workerKey] = {
 456       worker,
 457       tasksUsage
 458     }
 459   }
 460 }