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     this.setupHook()
  77
  78     for (let i = 1; i <= this.numberOfWorkers; i++) {
  79       this.createAndSetupWorker()
  80     }
  81
  82     if (this.opts.enableEvents === true) {
  83       this.emitter = new PoolEmitter()
  84     }
  85     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext(
  86       this,
  87       () => {
  88         const createdWorker = this.createAndSetupWorker()
  89         this.registerWorkerMessageListener(createdWorker, message => {
  90           if (
  91             isKillBehavior(KillBehaviors.HARD, message.kill) ||
  92             this.getWorkerTasksUsage(createdWorker)?.running === 0
  93           ) {
  94             // Kill received from the worker, means that no new tasks are submitted to that worker for a while ( > maxInactiveTime)
  95             void this.destroyWorker(createdWorker)
  96           }
  97         })
  98         return this.getWorkerKey(createdWorker)
  99       },
 100       this.opts.workerChoiceStrategy
 101     )
 102   }
 103
 104   private checkFilePath (filePath: string): void {
 105     if (
 106       filePath == null ||
 107       (typeof filePath === 'string' && filePath.trim().length === 0)
 108     ) {
 109       throw new Error('Please specify a file with a worker implementation')
 110     }
 111   }
 112
 113   private checkNumberOfWorkers (numberOfWorkers: number): void {
 114     if (numberOfWorkers == null) {
 115       throw new Error(
 116         'Cannot instantiate a pool without specifying the number of workers'
 117       )
 118     } else if (!Number.isSafeInteger(numberOfWorkers)) {
 119       throw new TypeError(
 120         'Cannot instantiate a pool with a non integer number of workers'
 121       )
 122     } else if (numberOfWorkers < 0) {
 123       throw new RangeError(
 124         'Cannot instantiate a pool with a negative number of workers'
 125       )
 126     } else if (this.type === PoolType.FIXED && numberOfWorkers === 0) {
 127       throw new Error('Cannot instantiate a fixed pool with no worker')
 128     }
 129   }
 130
 131   private checkPoolOptions (opts: PoolOptions<Worker>): void {
 132     this.opts.workerChoiceStrategy =
 133       opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
 134     this.opts.enableEvents = opts.enableEvents ?? true
 135   }
 136
 137   /** {@inheritDoc} */
 138   public abstract get type (): PoolType
 139
 140   /** {@inheritDoc} */
 141   public get numberOfRunningTasks (): number {
 142     return this.promiseResponseMap.size
 143   }
 144
 145   /**
 146    * Gets the given worker key.
 147    *
 148    * @param worker - The worker.
 149    * @returns The worker key if the worker is found in the pool, `-1` otherwise.
 150    */
 151   private getWorkerKey (worker: Worker): number {
 152     return this.workers.findIndex(workerItem => workerItem.worker === worker)
 153   }
 154
 155   /** {@inheritDoc} */
 156   public setWorkerChoiceStrategy (
 157     workerChoiceStrategy: WorkerChoiceStrategy
 158   ): void {
 159     this.opts.workerChoiceStrategy = workerChoiceStrategy
 160     for (const [index, workerItem] of this.workers.entries()) {
 161       this.setWorker(index, workerItem.worker, {
 162         run: 0,
 163         running: 0,
 164         runTime: 0,
 165         avgRunTime: 0,
 166         error: 0
 167       })
 168     }
 169     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 170       workerChoiceStrategy
 171     )
 172   }
 173
 174   /** {@inheritDoc} */
 175   public abstract get busy (): boolean
 176
 177   protected internalGetBusyStatus (): boolean {
 178     return (
 179       this.numberOfRunningTasks >= this.numberOfWorkers &&
 180       this.findFreeWorkerKey() === false
 181     )
 182   }
 183
 184   /** {@inheritDoc} */
 185   public findFreeWorkerKey (): number | false {
 186     const freeWorkerKey = this.workers.findIndex(workerItem => {
 187       return workerItem.tasksUsage.running === 0
 188     })
 189     return freeWorkerKey !== -1 ? freeWorkerKey : false
 190   }
 191
 192   /** {@inheritDoc} */
 193   public async execute (data: Data): Promise<Response> {
 194     const [workerKey, worker] = this.chooseWorker()
 195     const messageId = crypto.randomUUID()
 196     const res = this.internalExecute(workerKey, worker, messageId)
 197     this.checkAndEmitBusy()
 198     this.sendToWorker(worker, {
 199       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 200       data: data ?? ({} as Data),
 201       id: messageId
 202     })
 203     // eslint-disable-next-line @typescript-eslint/return-await
 204     return res
 205   }
 206
 207   /** {@inheritDoc} */
 208   public async destroy (): Promise<void> {
 209     await Promise.all(
 210       this.workers.map(async workerItem => {
 211         await this.destroyWorker(workerItem.worker)
 212       })
 213     )
 214   }
 215
 216   /**
 217    * Shutdowns given worker.
 218    *
 219    * @param worker - A worker within `workers`.
 220    */
 221   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 222
 223   /**
 224    * Setup hook that can be overridden by a Poolifier pool implementation
 225    * to run code before workers are created in the abstract constructor.
 226    */
 227   protected setupHook (): void {
 228     // Can be overridden
 229   }
 230
 231   /**
 232    * Should return whether the worker is the main worker or not.
 233    */
 234   protected abstract isMain (): boolean
 235
 236   /**
 237    * Hook executed before the worker task promise resolution.
 238    * Can be overridden.
 239    *
 240    * @param workerKey - The worker key.
 241    */
 242   protected beforePromiseResponseHook (workerKey: number): void {
 243     ++this.workers[workerKey].tasksUsage.running
 244   }
 245
 246   /**
 247    * Hook executed after the worker task promise resolution.
 248    * Can be overridden.
 249    *
 250    * @param worker - The worker.
 251    * @param message - The received message.
 252    */
 253   protected afterPromiseResponseHook (
 254     worker: Worker,
 255     message: MessageValue<Response>
 256   ): void {
 257     const workerTasksUsage = this.getWorkerTasksUsage(worker) as TasksUsage
 258     --workerTasksUsage.running
 259     ++workerTasksUsage.run
 260     if (message.error != null) {
 261       ++workerTasksUsage.error
 262     }
 263     if (this.workerChoiceStrategyContext.getRequiredStatistics().runTime) {
 264       workerTasksUsage.runTime += message.taskRunTime ?? 0
 265       if (workerTasksUsage.run !== 0) {
 266         workerTasksUsage.avgRunTime =
 267           workerTasksUsage.runTime / workerTasksUsage.run
 268       }
 269     }
 270   }
 271
 272   /**
 273    * Removes the given worker from the pool.
 274    *
 275    * @param worker - The worker that will be removed.
 276    */
 277   protected removeWorker (worker: Worker): void {
 278     const workerKey = this.getWorkerKey(worker)
 279     this.workers.splice(workerKey, 1)
 280     this.workerChoiceStrategyContext.remove(workerKey)
 281   }
 282
 283   /**
 284    * Chooses a worker for the next task.
 285    *
 286    * The default implementation uses a round robin algorithm to distribute the load.
 287    *
 288    * @returns [worker key, worker].
 289    */
 290   protected chooseWorker (): [number, Worker] {
 291     const workerKey = this.workerChoiceStrategyContext.execute()
 292     return [workerKey, this.workers[workerKey].worker]
 293   }
 294
 295   /**
 296    * Sends a message to the given worker.
 297    *
 298    * @param worker - The worker which should receive the message.
 299    * @param message - The message.
 300    */
 301   protected abstract sendToWorker (
 302     worker: Worker,
 303     message: MessageValue<Data>
 304   ): void
 305
 306   /**
 307    * Registers a listener callback on a given worker.
 308    *
 309    * @param worker - The worker which should register a listener.
 310    * @param listener - The message listener callback.
 311    */
 312   protected abstract registerWorkerMessageListener<
 313     Message extends Data | Response
 314   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 315
 316   /**
 317    * Returns a newly created worker.
 318    */
 319   protected abstract createWorker (): Worker
 320
 321   /**
 322    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 323    *
 324    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 325    *
 326    * @param worker - The newly created worker.
 327    */
 328   protected abstract afterWorkerSetup (worker: Worker): void
 329
 330   /**
 331    * Creates a new worker for this pool and sets it up completely.
 332    *
 333    * @returns New, completely set up worker.
 334    */
 335   protected createAndSetupWorker (): Worker {
 336     const worker = this.createWorker()
 337
 338     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 339     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 340     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 341     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 342     worker.once('exit', () => {
 343       this.removeWorker(worker)
 344     })
 345
 346     this.pushWorker(worker, {
 347       run: 0,
 348       running: 0,
 349       runTime: 0,
 350       avgRunTime: 0,
 351       error: 0
 352     })
 353
 354     this.afterWorkerSetup(worker)
 355
 356     return worker
 357   }
 358
 359   /**
 360    * This function is the listener registered for each worker.
 361    *
 362    * @returns The listener function to execute when a message is received from a worker.
 363    */
 364   protected workerListener (): (message: MessageValue<Response>) => void {
 365     return message => {
 366       if (message.id !== undefined) {
 367         const promiseResponse = this.promiseResponseMap.get(message.id)
 368         if (promiseResponse !== undefined) {
 369           if (message.error != null) {
 370             promiseResponse.reject(message.error)
 371           } else {
 372             promiseResponse.resolve(message.data as Response)
 373           }
 374           this.afterPromiseResponseHook(promiseResponse.worker, message)
 375           this.promiseResponseMap.delete(message.id)
 376         }
 377       }
 378     }
 379   }
 380
 381   private async internalExecute (
 382     workerKey: number,
 383     worker: Worker,
 384     messageId: string
 385   ): Promise<Response> {
 386     this.beforePromiseResponseHook(workerKey)
 387     return await new Promise<Response>((resolve, reject) => {
 388       this.promiseResponseMap.set(messageId, { resolve, reject, worker })
 389     })
 390   }
 391
 392   private checkAndEmitBusy (): void {
 393     if (this.opts.enableEvents === true && this.busy) {
 394       this.emitter?.emit('busy')
 395     }
 396   }
 397
 398   /**
 399    * Gets worker tasks usage.
 400    *
 401    * @param worker - The worker.
 402    * @returns The worker tasks usage.
 403    */
 404   private getWorkerTasksUsage (worker: Worker): TasksUsage | undefined {
 405     const workerKey = this.getWorkerKey(worker)
 406     if (workerKey !== -1) {
 407       return this.workers[workerKey].tasksUsage
 408     }
 409     throw new Error('Worker could not be found in the pool')
 410   }
 411
 412   /**
 413    * Pushes the given worker.
 414    *
 415    * @param worker - The worker.
 416    * @param tasksUsage - The worker tasks usage.
 417    */
 418   private pushWorker (worker: Worker, tasksUsage: TasksUsage): void {
 419     this.workers.push({
 420       worker,
 421       tasksUsage
 422     })
 423   }
 424
 425   /**
 426    * Sets the given worker.
 427    *
 428    * @param workerKey - The worker key.
 429    * @param worker - The worker.
 430    * @param tasksUsage - The worker tasks usage.
 431    */
 432   private setWorker (
 433     workerKey: number,
 434     worker: Worker,
 435     tasksUsage: TasksUsage
 436   ): void {
 437     this.workers[workerKey] = {
 438       worker,
 439       tasksUsage
 440     }
 441   }
 442 }