src/pools/abstract-pool.ts

   1 import type {
   2   MessageValue,
   3   PromiseWorkerResponseWrapper
   4 } from '../utility-types'
   5 import { EMPTY_FUNCTION, EMPTY_LITERAL } from '../utils'
   6 import { isKillBehavior, KillBehaviors } from '../worker/worker-options'
   7 import type { PoolOptions } from './pool'
   8 import { PoolEmitter } from './pool'
   9 import type { IPoolInternal, TasksUsage } from './pool-internal'
  10 import { PoolType } from './pool-internal'
  11 import type { IPoolWorker } from './pool-worker'
  12 import {
  13   WorkerChoiceStrategies,
  14   WorkerChoiceStrategy
  15 } from './selection-strategies/selection-strategies-types'
  16 import { WorkerChoiceStrategyContext } from './selection-strategies/worker-choice-strategy-context'
  17
  18 /**
  19  * Base class that implements some shared logic for all poolifier pools.
  20  *
  21  * @template Worker Type of worker which manages this pool.
  22  * @template Data Type of data sent to the worker. This can only be serializable data.
  23  * @template Response Type of response of execution. This can only be serializable data.
  24  */
  25 export abstract class AbstractPool<
  26   Worker extends IPoolWorker,
  27   Data = unknown,
  28   Response = unknown
  29 > implements IPoolInternal<Worker, Data, Response> {
  30   /** @inheritDoc */
  31   public readonly workers: Worker[] = []
  32
  33   /** @inheritDoc */
  34   public readonly workersTasksUsage: Map<Worker, TasksUsage> = new Map<
  35   Worker,
  36   TasksUsage
  37   >()
  38
  39   /** @inheritDoc */
  40   public readonly emitter?: PoolEmitter
  41
  42   /**
  43    * The promise map.
  44    *
  45    * - `key`: This is the message Id of each submitted task.
  46    * - `value`: An object that contains the worker, the resolve function and the reject function.
  47    *
  48    * When we receive a message from the worker we get a map entry and resolve/reject the promise based on the message.
  49    */
  50   protected promiseMap: Map<
  51   number,
  52   PromiseWorkerResponseWrapper<Worker, Response>
  53   > = new Map<number, PromiseWorkerResponseWrapper<Worker, Response>>()
  54
  55   /**
  56    * Id of the next message.
  57    */
  58   protected nextMessageId: number = 0
  59
  60   /**
  61    * Worker choice strategy instance implementing the worker choice algorithm.
  62    *
  63    * Default to a strategy implementing a round robin algorithm.
  64    */
  65   protected workerChoiceStrategyContext: WorkerChoiceStrategyContext<
  66   Worker,
  67   Data,
  68   Response
  69   >
  70
  71   /**
  72    * Constructs a new poolifier pool.
  73    *
  74    * @param numberOfWorkers Number of workers that this pool should manage.
  75    * @param filePath Path to the worker-file.
  76    * @param opts Options for the pool.
  77    */
  78   public constructor (
  79     public readonly numberOfWorkers: number,
  80     public readonly filePath: string,
  81     public readonly opts: PoolOptions<Worker>
  82   ) {
  83     if (!this.isMain()) {
  84       throw new Error('Cannot start a pool from a worker!')
  85     }
  86     this.checkNumberOfWorkers(this.numberOfWorkers)
  87     this.checkFilePath(this.filePath)
  88     this.checkPoolOptions(this.opts)
  89     this.setupHook()
  90
  91     for (let i = 1; i <= this.numberOfWorkers; i++) {
  92       this.createAndSetupWorker()
  93     }
  94
  95     if (this.opts.enableEvents === true) {
  96       this.emitter = new PoolEmitter()
  97     }
  98     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext(
  99       this,
 100       () => {
 101         const workerCreated = this.createAndSetupWorker()
 102         this.registerWorkerMessageListener(workerCreated, message => {
 103           if (
 104             isKillBehavior(KillBehaviors.HARD, message.kill) ||
 105             this.getWorkerRunningTasks(workerCreated) === 0
 106           ) {
 107             // Kill received from the worker, means that no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 108             void this.destroyWorker(workerCreated)
 109           }
 110         })
 111         return workerCreated
 112       },
 113       this.opts.workerChoiceStrategy
 114     )
 115   }
 116
 117   private checkFilePath (filePath: string): void {
 118     if (filePath == null || filePath.length === 0) {
 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   /** @inheritDoc */
 151   public get numberOfRunningTasks (): number {
 152     return this.promiseMap.size
 153   }
 154
 155   /** @inheritDoc */
 156   public getWorkerIndex (worker: Worker): number {
 157     return this.workers.indexOf(worker)
 158   }
 159
 160   /** @inheritDoc */
 161   public getWorkerRunningTasks (worker: Worker): number | undefined {
 162     return this.workersTasksUsage.get(worker)?.running
 163   }
 164
 165   /** @inheritDoc */
 166   public getWorkerAverageTasksRunTime (worker: Worker): number | undefined {
 167     return this.workersTasksUsage.get(worker)?.avgRunTime
 168   }
 169
 170   /** @inheritDoc */
 171   public setWorkerChoiceStrategy (
 172     workerChoiceStrategy: WorkerChoiceStrategy
 173   ): void {
 174     this.opts.workerChoiceStrategy = workerChoiceStrategy
 175     for (const worker of this.workers) {
 176       this.resetWorkerTasksUsage(worker)
 177     }
 178     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 179       workerChoiceStrategy
 180     )
 181   }
 182
 183   /** @inheritDoc */
 184   public abstract get busy (): boolean
 185
 186   protected internalGetBusyStatus (): boolean {
 187     return (
 188       this.numberOfRunningTasks >= this.numberOfWorkers &&
 189       this.findFreeWorker() === false
 190     )
 191   }
 192
 193   /** @inheritDoc */
 194   public findFreeWorker (): Worker | false {
 195     for (const worker of this.workers) {
 196       if (this.getWorkerRunningTasks(worker) === 0) {
 197         // A worker is free, return the matching worker
 198         return worker
 199       }
 200     }
 201     return false
 202   }
 203
 204   /** @inheritDoc */
 205   public async execute (data: Data): Promise<Response> {
 206     // Configure worker to handle message with the specified task
 207     const worker = this.chooseWorker()
 208     const res = this.internalExecute(worker, this.nextMessageId)
 209     this.checkAndEmitBusy()
 210     this.sendToWorker(worker, {
 211       data: data ?? (EMPTY_LITERAL as Data),
 212       id: this.nextMessageId
 213     })
 214     ++this.nextMessageId
 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(this.workers.map(worker => this.destroyWorker(worker)))
 222   }
 223
 224   /**
 225    * Shutdowns given worker.
 226    *
 227    * @param worker A worker within `workers`.
 228    */
 229   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 230
 231   /**
 232    * Setup hook that can be overridden by a Poolifier pool implementation
 233    * to run code before workers are created in the abstract constructor.
 234    */
 235   protected setupHook (): void {
 236     // Can be overridden
 237   }
 238
 239   /**
 240    * Should return whether the worker is the main worker or not.
 241    */
 242   protected abstract isMain (): boolean
 243
 244   /**
 245    * Hook executed before the worker task promise resolution.
 246    * Can be overridden.
 247    *
 248    * @param worker The worker.
 249    */
 250   protected beforePromiseWorkerResponseHook (worker: Worker): void {
 251     this.increaseWorkerRunningTasks(worker)
 252   }
 253
 254   /**
 255    * Hook executed after the worker task promise resolution.
 256    * Can be overridden.
 257    *
 258    * @param message The received message.
 259    * @param promise The Promise response.
 260    */
 261   protected afterPromiseWorkerResponseHook (
 262     message: MessageValue<Response>,
 263     promise: PromiseWorkerResponseWrapper<Worker, Response>
 264   ): void {
 265     this.decreaseWorkerRunningTasks(promise.worker)
 266     this.stepWorkerRunTasks(promise.worker, 1)
 267     this.updateWorkerTasksRunTime(promise.worker, message.taskRunTime)
 268   }
 269
 270   /**
 271    * Removes the given worker from the pool.
 272    *
 273    * @param worker The worker that will be removed.
 274    */
 275   protected removeWorker (worker: Worker): void {
 276     // Clean worker from data structure
 277     this.workers.splice(this.getWorkerIndex(worker), 1)
 278     this.removeWorkerTasksUsage(worker)
 279   }
 280
 281   /**
 282    * Chooses a worker for the next task.
 283    *
 284    * The default implementation uses a round robin algorithm to distribute the load.
 285    *
 286    * @returns Worker.
 287    */
 288   protected chooseWorker (): Worker {
 289     return this.workerChoiceStrategyContext.execute()
 290   }
 291
 292   /**
 293    * Sends a message to the given worker.
 294    *
 295    * @param worker The worker which should receive the message.
 296    * @param message The message.
 297    */
 298   protected abstract sendToWorker (
 299     worker: Worker,
 300     message: MessageValue<Data>
 301   ): void
 302
 303   /**
 304    * Registers a listener callback on a given worker.
 305    *
 306    * @param worker The worker which should register a listener.
 307    * @param listener The message listener callback.
 308    */
 309   protected abstract registerWorkerMessageListener<
 310     Message extends Data | Response
 311   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 312
 313   /**
 314    * Returns a newly created worker.
 315    */
 316   protected abstract createWorker (): Worker
 317
 318   /**
 319    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 320    *
 321    * Can be used to update the `maxListeners` or binding the `main-worker`<->`worker` connection if not bind by default.
 322    *
 323    * @param worker The newly created worker.
 324    */
 325   protected abstract afterWorkerSetup (worker: Worker): void
 326
 327   /**
 328    * Creates a new worker for this pool and sets it up completely.
 329    *
 330    * @returns New, completely set up worker.
 331    */
 332   protected createAndSetupWorker (): Worker {
 333     const worker = this.createWorker()
 334
 335     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 336     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 337     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 338     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 339     worker.once('exit', () => this.removeWorker(worker))
 340
 341     this.workers.push(worker)
 342
 343     // Init worker tasks usage map
 344     this.initWorkerTasksUsage(worker)
 345
 346     this.afterWorkerSetup(worker)
 347
 348     return worker
 349   }
 350
 351   /**
 352    * This function is the listener registered for each worker.
 353    *
 354    * @returns The listener function to execute when a message is received from a worker.
 355    */
 356   protected workerListener (): (message: MessageValue<Response>) => void {
 357     return message => {
 358       if (message.id !== undefined) {
 359         const promise = this.promiseMap.get(message.id)
 360         if (promise !== undefined) {
 361           if (message.error != null) {
 362             promise.reject(message.error)
 363           } else {
 364             promise.resolve(message.data as Response)
 365           }
 366           this.afterPromiseWorkerResponseHook(message, promise)
 367           this.promiseMap.delete(message.id)
 368         }
 369       }
 370     }
 371   }
 372
 373   private async internalExecute (
 374     worker: Worker,
 375     messageId: number
 376   ): Promise<Response> {
 377     this.beforePromiseWorkerResponseHook(worker)
 378     return await new Promise<Response>((resolve, reject) => {
 379       this.promiseMap.set(messageId, { resolve, reject, worker })
 380     })
 381   }
 382
 383   private checkAndEmitBusy (): void {
 384     if (this.opts.enableEvents === true && this.busy) {
 385       this.emitter?.emit('busy')
 386     }
 387   }
 388
 389   /**
 390    * Increases the number of tasks that the given worker has applied.
 391    *
 392    * @param worker Worker which running tasks is increased.
 393    */
 394   private increaseWorkerRunningTasks (worker: Worker): void {
 395     this.stepWorkerRunningTasks(worker, 1)
 396   }
 397
 398   /**
 399    * Decreases the number of tasks that the given worker has applied.
 400    *
 401    * @param worker Worker which running tasks is decreased.
 402    */
 403   private decreaseWorkerRunningTasks (worker: Worker): void {
 404     this.stepWorkerRunningTasks(worker, -1)
 405   }
 406
 407   /**
 408    * Steps the number of tasks that the given worker has applied.
 409    *
 410    * @param worker Worker which running tasks are stepped.
 411    * @param step Number of running tasks step.
 412    */
 413   private stepWorkerRunningTasks (worker: Worker, step: number): void {
 414     if (this.checkWorkerTasksUsage(worker)) {
 415       const tasksUsage = this.workersTasksUsage.get(worker) as TasksUsage
 416       tasksUsage.running = tasksUsage.running + step
 417       this.workersTasksUsage.set(worker, tasksUsage)
 418     }
 419   }
 420
 421   /**
 422    * Steps the number of tasks that the given worker has run.
 423    *
 424    * @param worker Worker which has run tasks.
 425    * @param step Number of run tasks step.
 426    */
 427   private stepWorkerRunTasks (worker: Worker, step: number): void {
 428     if (this.checkWorkerTasksUsage(worker)) {
 429       const tasksUsage = this.workersTasksUsage.get(worker) as TasksUsage
 430       tasksUsage.run = tasksUsage.run + step
 431       this.workersTasksUsage.set(worker, tasksUsage)
 432     }
 433   }
 434
 435   /**
 436    * Updates tasks runtime for the given worker.
 437    *
 438    * @param worker Worker which run the task.
 439    * @param taskRunTime Worker task runtime.
 440    */
 441   private updateWorkerTasksRunTime (
 442     worker: Worker,
 443     taskRunTime: number | undefined
 444   ): void {
 445     if (
 446       this.workerChoiceStrategyContext.getWorkerChoiceStrategy()
 447         .requiredStatistics.runTime &&
 448       this.checkWorkerTasksUsage(worker)
 449     ) {
 450       const tasksUsage = this.workersTasksUsage.get(worker) as TasksUsage
 451       tasksUsage.runTime += taskRunTime ?? 0
 452       if (tasksUsage.run !== 0) {
 453         tasksUsage.avgRunTime = tasksUsage.runTime / tasksUsage.run
 454       }
 455       this.workersTasksUsage.set(worker, tasksUsage)
 456     }
 457   }
 458
 459   /**
 460    * Checks if the given worker is registered in the workers tasks usage map.
 461    *
 462    * @param worker Worker to check.
 463    * @returns `true` if the worker is registered in the workers tasks usage map. `false` otherwise.
 464    */
 465   private checkWorkerTasksUsage (worker: Worker): boolean {
 466     const hasTasksUsage = this.workersTasksUsage.has(worker)
 467     if (!hasTasksUsage) {
 468       throw new Error('Worker could not be found in workers tasks usage map')
 469     }
 470     return hasTasksUsage
 471   }
 472
 473   /**
 474    * Initializes tasks usage statistics.
 475    *
 476    * @param worker The worker.
 477    */
 478   private initWorkerTasksUsage (worker: Worker): void {
 479     this.workersTasksUsage.set(worker, {
 480       run: 0,
 481       running: 0,
 482       runTime: 0,
 483       avgRunTime: 0
 484     })
 485   }
 486
 487   /**
 488    * Removes worker tasks usage statistics.
 489    *
 490    * @param worker The worker.
 491    */
 492   private removeWorkerTasksUsage (worker: Worker): void {
 493     this.workersTasksUsage.delete(worker)
 494   }
 495
 496   /**
 497    * Resets worker tasks usage statistics.
 498    *
 499    * @param worker The worker.
 500    */
 501   private resetWorkerTasksUsage (worker: Worker): void {
 502     this.removeWorkerTasksUsage(worker)
 503     this.initWorkerTasksUsage(worker)
 504   }
 505 }