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.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     >(
  97       this,
  98       () => {
  99         const createdWorker = this.createAndSetupWorker()
 100         this.registerWorkerMessageListener(createdWorker, message => {
 101           if (
 102             isKillBehavior(KillBehaviors.HARD, message.kill) ||
 103             this.getWorkerTasksUsage(createdWorker)?.running === 0
 104           ) {
 105             // Kill received from the worker, means that no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 106             void this.destroyWorker(createdWorker)
 107           }
 108         })
 109         return this.getWorkerKey(createdWorker)
 110       },
 111       this.opts.workerChoiceStrategy
 112     )
 113   }
 114
 115   private checkFilePath (filePath: string): void {
 116     if (
 117       filePath == null ||
 118       (typeof filePath === 'string' && filePath.trim().length === 0)
 119     ) {
 120       throw new Error('Please specify a file with a worker implementation')
 121     }
 122   }
 123
 124   private checkNumberOfWorkers (numberOfWorkers: number): void {
 125     if (numberOfWorkers == null) {
 126       throw new Error(
 127         'Cannot instantiate a pool without specifying the number of workers'
 128       )
 129     } else if (!Number.isSafeInteger(numberOfWorkers)) {
 130       throw new TypeError(
 131         'Cannot instantiate a pool with a non integer number of workers'
 132       )
 133     } else if (numberOfWorkers < 0) {
 134       throw new RangeError(
 135         'Cannot instantiate a pool with a negative number of workers'
 136       )
 137     } else if (this.type === PoolType.FIXED && numberOfWorkers === 0) {
 138       throw new Error('Cannot instantiate a fixed pool with no worker')
 139     }
 140   }
 141
 142   private checkPoolOptions (opts: PoolOptions<Worker>): void {
 143     this.opts.workerChoiceStrategy =
 144       opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
 145     this.opts.enableEvents = opts.enableEvents ?? true
 146   }
 147
 148   /** {@inheritDoc} */
 149   public abstract get type (): PoolType
 150
 151   /**
 152    * Number of tasks concurrently running.
 153    */
 154   private get numberOfRunningTasks (): number {
 155     return this.promiseResponseMap.size
 156   }
 157
 158   /**
 159    * Gets the given worker key.
 160    *
 161    * @param worker - The worker.
 162    * @returns The worker key if the worker is found in the pool, `-1` otherwise.
 163    */
 164   private getWorkerKey (worker: Worker): number {
 165     return this.workers.findIndex(workerItem => workerItem.worker === worker)
 166   }
 167
 168   /** {@inheritDoc} */
 169   public setWorkerChoiceStrategy (
 170     workerChoiceStrategy: WorkerChoiceStrategy
 171   ): void {
 172     this.opts.workerChoiceStrategy = workerChoiceStrategy
 173     for (const [index, workerItem] of this.workers.entries()) {
 174       this.setWorker(index, workerItem.worker, {
 175         run: 0,
 176         running: 0,
 177         runTime: 0,
 178         avgRunTime: 0,
 179         error: 0
 180       })
 181     }
 182     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 183       this,
 184       workerChoiceStrategy
 185     )
 186   }
 187
 188   /** {@inheritDoc} */
 189   public abstract get full (): boolean
 190
 191   /** {@inheritDoc} */
 192   public abstract get busy (): boolean
 193
 194   protected internalBusy (): boolean {
 195     return (
 196       this.numberOfRunningTasks >= this.numberOfWorkers &&
 197       this.findFreeWorkerKey() === -1
 198     )
 199   }
 200
 201   /** {@inheritDoc} */
 202   public findFreeWorkerKey (): number {
 203     return this.workers.findIndex(workerItem => {
 204       return workerItem.tasksUsage.running === 0
 205     })
 206   }
 207
 208   /** {@inheritDoc} */
 209   public async execute (data: Data): Promise<Response> {
 210     const [workerKey, worker] = this.chooseWorker()
 211     const messageId = crypto.randomUUID()
 212     const res = this.internalExecute(workerKey, worker, messageId)
 213     this.checkAndEmitFull()
 214     this.checkAndEmitBusy()
 215     this.sendToWorker(worker, {
 216       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 217       data: data ?? ({} as Data),
 218       id: messageId
 219     })
 220     // eslint-disable-next-line @typescript-eslint/return-await
 221     return res
 222   }
 223
 224   /** {@inheritDoc} */
 225   public async destroy (): Promise<void> {
 226     await Promise.all(
 227       this.workers.map(async workerItem => {
 228         await this.destroyWorker(workerItem.worker)
 229       })
 230     )
 231   }
 232
 233   /**
 234    * Shutdowns given worker.
 235    *
 236    * @param worker - A worker within `workers`.
 237    */
 238   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 239
 240   /**
 241    * Setup hook that can be overridden by a Poolifier pool implementation
 242    * to run code before workers are created in the abstract constructor.
 243    */
 244   protected setupHook (): void {
 245     // Can be overridden
 246   }
 247
 248   /**
 249    * Should return whether the worker is the main worker or not.
 250    */
 251   protected abstract isMain (): boolean
 252
 253   /**
 254    * Hook executed before the worker task promise resolution.
 255    * Can be overridden.
 256    *
 257    * @param workerKey - The worker key.
 258    */
 259   protected beforePromiseResponseHook (workerKey: number): void {
 260     ++this.workers[workerKey].tasksUsage.running
 261   }
 262
 263   /**
 264    * Hook executed after the worker task promise resolution.
 265    * Can be overridden.
 266    *
 267    * @param worker - The worker.
 268    * @param message - The received message.
 269    */
 270   protected afterPromiseResponseHook (
 271     worker: Worker,
 272     message: MessageValue<Response>
 273   ): void {
 274     const workerTasksUsage = this.getWorkerTasksUsage(worker) as TasksUsage
 275     --workerTasksUsage.running
 276     ++workerTasksUsage.run
 277     if (message.error != null) {
 278       ++workerTasksUsage.error
 279     }
 280     if (this.workerChoiceStrategyContext.getRequiredStatistics().runTime) {
 281       workerTasksUsage.runTime += message.taskRunTime ?? 0
 282       if (
 283         this.workerChoiceStrategyContext.getRequiredStatistics().avgRunTime &&
 284         workerTasksUsage.run !== 0
 285       ) {
 286         workerTasksUsage.avgRunTime =
 287           workerTasksUsage.runTime / workerTasksUsage.run
 288       }
 289     }
 290   }
 291
 292   /**
 293    * Removes the given worker from the pool.
 294    *
 295    * @param worker - The worker that will be removed.
 296    */
 297   protected removeWorker (worker: Worker): void {
 298     const workerKey = this.getWorkerKey(worker)
 299     this.workers.splice(workerKey, 1)
 300     this.workerChoiceStrategyContext.remove(workerKey)
 301   }
 302
 303   /**
 304    * Chooses a worker for the next task.
 305    *
 306    * The default implementation uses a round robin algorithm to distribute the load.
 307    *
 308    * @returns [worker key, worker].
 309    */
 310   protected chooseWorker (): [number, Worker] {
 311     const workerKey = this.workerChoiceStrategyContext.execute()
 312     return [workerKey, this.workers[workerKey].worker]
 313   }
 314
 315   /**
 316    * Sends a message to the given worker.
 317    *
 318    * @param worker - The worker which should receive the message.
 319    * @param message - The message.
 320    */
 321   protected abstract sendToWorker (
 322     worker: Worker,
 323     message: MessageValue<Data>
 324   ): void
 325
 326   /**
 327    * Registers a listener callback on a given worker.
 328    *
 329    * @param worker - The worker which should register a listener.
 330    * @param listener - The message listener callback.
 331    */
 332   protected abstract registerWorkerMessageListener<
 333     Message extends Data | Response
 334   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 335
 336   /**
 337    * Returns a newly created worker.
 338    */
 339   protected abstract createWorker (): Worker
 340
 341   /**
 342    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 343    *
 344    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 345    *
 346    * @param worker - The newly created worker.
 347    */
 348   protected abstract afterWorkerSetup (worker: Worker): void
 349
 350   /**
 351    * Creates a new worker for this pool and sets it up completely.
 352    *
 353    * @returns New, completely set up worker.
 354    */
 355   protected createAndSetupWorker (): Worker {
 356     const worker = this.createWorker()
 357
 358     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 359     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 360     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 361     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 362     worker.once('exit', () => {
 363       this.removeWorker(worker)
 364     })
 365
 366     this.pushWorker(worker, {
 367       run: 0,
 368       running: 0,
 369       runTime: 0,
 370       avgRunTime: 0,
 371       error: 0
 372     })
 373
 374     this.afterWorkerSetup(worker)
 375
 376     return worker
 377   }
 378
 379   /**
 380    * This function is the listener registered for each worker.
 381    *
 382    * @returns The listener function to execute when a message is received from a worker.
 383    */
 384   protected workerListener (): (message: MessageValue<Response>) => void {
 385     return message => {
 386       if (message.id !== undefined) {
 387         const promiseResponse = this.promiseResponseMap.get(message.id)
 388         if (promiseResponse !== undefined) {
 389           if (message.error != null) {
 390             promiseResponse.reject(message.error)
 391           } else {
 392             promiseResponse.resolve(message.data as Response)
 393           }
 394           this.afterPromiseResponseHook(promiseResponse.worker, message)
 395           this.promiseResponseMap.delete(message.id)
 396         }
 397       }
 398     }
 399   }
 400
 401   private async internalExecute (
 402     workerKey: number,
 403     worker: Worker,
 404     messageId: string
 405   ): Promise<Response> {
 406     this.beforePromiseResponseHook(workerKey)
 407     return await new Promise<Response>((resolve, reject) => {
 408       this.promiseResponseMap.set(messageId, { resolve, reject, worker })
 409     })
 410   }
 411
 412   private checkAndEmitBusy (): void {
 413     if (this.opts.enableEvents === true && this.busy) {
 414       this.emitter?.emit('busy')
 415     }
 416   }
 417
 418   private checkAndEmitFull (): void {
 419     if (
 420       this.type === PoolType.DYNAMIC &&
 421       this.opts.enableEvents === true &&
 422       this.full
 423     ) {
 424       this.emitter?.emit('full')
 425     }
 426   }
 427
 428   /**
 429    * Gets worker tasks usage.
 430    *
 431    * @param worker - The worker.
 432    * @returns The worker tasks usage.
 433    */
 434   private getWorkerTasksUsage (worker: Worker): TasksUsage | undefined {
 435     const workerKey = this.getWorkerKey(worker)
 436     if (workerKey !== -1) {
 437       return this.workers[workerKey].tasksUsage
 438     }
 439     throw new Error('Worker could not be found in the pool')
 440   }
 441
 442   /**
 443    * Pushes the given worker.
 444    *
 445    * @param worker - The worker.
 446    * @param tasksUsage - The worker tasks usage.
 447    */
 448   private pushWorker (worker: Worker, tasksUsage: TasksUsage): void {
 449     this.workers.push({
 450       worker,
 451       tasksUsage
 452     })
 453   }
 454
 455   /**
 456    * Sets the given worker.
 457    *
 458    * @param workerKey - The worker key.
 459    * @param worker - The worker.
 460    * @param tasksUsage - The worker tasks usage.
 461    */
 462   private setWorker (
 463     workerKey: number,
 464     worker: Worker,
 465     tasksUsage: TasksUsage
 466   ): void {
 467     this.workers[workerKey] = {
 468       worker,
 469       tasksUsage
 470     }
 471   }
 472 }