src/pools/abstract-pool.ts

   1 import type {
   2   MessageValue,
   3   PromiseWorkerResponseWrapper
   4 } from '../utility-types'
   5 import { EMPTY_FUNCTION } 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() === false) {
  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             this.destroyWorker(workerCreated) as void
 109           }
 110         })
 111         return workerCreated
 112       },
 113       this.opts.workerChoiceStrategy
 114     )
 115   }
 116
 117   private checkFilePath (filePath: string): void {
 118     if (!filePath) {
 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) === false) {
 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 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 ?? ({} as Data),
 212       id: this.nextMessageId
 213     })
 214     ++this.nextMessageId
 215     return res
 216   }
 217
 218   /** @inheritDoc */
 219   public async destroy (): Promise<void> {
 220     await Promise.all(this.workers.map(worker => this.destroyWorker(worker)))
 221   }
 222
 223   /**
 224    * Shutdowns given worker.
 225    *
 226    * @param worker A worker within `workers`.
 227    */
 228   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 229
 230   /**
 231    * Setup hook that can be overridden by a Poolifier pool implementation
 232    * to run code before workers are created in the abstract constructor.
 233    */
 234   protected setupHook (): void {
 235     // Can be overridden
 236   }
 237
 238   /**
 239    * Should return whether the worker is the main worker or not.
 240    */
 241   protected abstract isMain (): boolean
 242
 243   /**
 244    * Hook executed before the worker task promise resolution.
 245    * Can be overridden.
 246    *
 247    * @param worker The worker.
 248    */
 249   protected beforePromiseWorkerResponseHook (worker: Worker): void {
 250     this.increaseWorkerRunningTasks(worker)
 251   }
 252
 253   /**
 254    * Hook executed after the worker task promise resolution.
 255    * Can be overridden.
 256    *
 257    * @param message The received message.
 258    * @param promise The Promise response.
 259    */
 260   protected afterPromiseWorkerResponseHook (
 261     message: MessageValue<Response>,
 262     promise: PromiseWorkerResponseWrapper<Worker, Response>
 263   ): void {
 264     this.decreaseWorkerRunningTasks(promise.worker)
 265     this.stepWorkerRunTasks(promise.worker, 1)
 266     this.updateWorkerTasksRunTime(promise.worker, message.taskRunTime)
 267   }
 268
 269   /**
 270    * Removes the given worker from the pool.
 271    *
 272    * @param worker The worker that will be removed.
 273    */
 274   protected removeWorker (worker: Worker): void {
 275     // Clean worker from data structure
 276     this.workers.splice(this.getWorkerIndex(worker), 1)
 277     this.removeWorkerTasksUsage(worker)
 278   }
 279
 280   /**
 281    * Chooses a worker for the next task.
 282    *
 283    * The default implementation uses a round robin algorithm to distribute the load.
 284    *
 285    * @returns Worker.
 286    */
 287   protected chooseWorker (): Worker {
 288     return this.workerChoiceStrategyContext.execute()
 289   }
 290
 291   /**
 292    * Sends a message to the given worker.
 293    *
 294    * @param worker The worker which should receive the message.
 295    * @param message The message.
 296    */
 297   protected abstract sendToWorker (
 298     worker: Worker,
 299     message: MessageValue<Data>
 300   ): void
 301
 302   /**
 303    * Registers a listener callback on a given worker.
 304    *
 305    * @param worker The worker which should register a listener.
 306    * @param listener The message listener callback.
 307    */
 308   protected abstract registerWorkerMessageListener<
 309     Message extends Data | Response
 310   > (worker: Worker, listener: (message: MessageValue<Message>) => void): void
 311
 312   protected internalExecute (
 313     worker: Worker,
 314     messageId: number
 315   ): Promise<Response> {
 316     this.beforePromiseWorkerResponseHook(worker)
 317     return new Promise<Response>((resolve, reject) => {
 318       this.promiseMap.set(messageId, { resolve, reject, worker })
 319     })
 320   }
 321
 322   /**
 323    * Returns a newly created worker.
 324    */
 325   protected abstract createWorker (): Worker
 326
 327   /**
 328    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 329    *
 330    * Can be used to update the `maxListeners` or binding the `main-worker`<->`worker` connection if not bind by default.
 331    *
 332    * @param worker The newly created worker.
 333    */
 334   protected abstract afterWorkerSetup (worker: Worker): void
 335
 336   /**
 337    * Creates a new worker for this pool and sets it up completely.
 338    *
 339    * @returns New, completely set up worker.
 340    */
 341   protected createAndSetupWorker (): Worker {
 342     const worker = this.createWorker()
 343
 344     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 345     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 346     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 347     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 348     worker.once('exit', () => this.removeWorker(worker))
 349
 350     this.workers.push(worker)
 351
 352     // Init worker tasks usage map
 353     this.initWorkerTasksUsage(worker)
 354
 355     this.afterWorkerSetup(worker)
 356
 357     return worker
 358   }
 359
 360   /**
 361    * This function is the listener registered for each worker.
 362    *
 363    * @returns The listener function to execute when a message is received from a worker.
 364    */
 365   protected workerListener (): (message: MessageValue<Response>) => void {
 366     return message => {
 367       if (message.id !== undefined) {
 368         const promise = this.promiseMap.get(message.id)
 369         if (promise !== undefined) {
 370           if (message.error) {
 371             promise.reject(message.error)
 372           } else {
 373             promise.resolve(message.data as Response)
 374           }
 375           this.afterPromiseWorkerResponseHook(message, promise)
 376           this.promiseMap.delete(message.id)
 377         }
 378       }
 379     }
 380   }
 381
 382   private checkAndEmitBusy (): void {
 383     if (this.opts.enableEvents === true && this.busy === true) {
 384       this.emitter?.emit('busy')
 385     }
 386   }
 387
 388   /**
 389    * Increases the number of tasks that the given worker has applied.
 390    *
 391    * @param worker Worker which running tasks is increased.
 392    */
 393   private increaseWorkerRunningTasks (worker: Worker): void {
 394     this.stepWorkerRunningTasks(worker, 1)
 395   }
 396
 397   /**
 398    * Decreases the number of tasks that the given worker has applied.
 399    *
 400    * @param worker Worker which running tasks is decreased.
 401    */
 402   private decreaseWorkerRunningTasks (worker: Worker): void {
 403     this.stepWorkerRunningTasks(worker, -1)
 404   }
 405
 406   /**
 407    * Steps the number of tasks that the given worker has applied.
 408    *
 409    * @param worker Worker which running tasks are stepped.
 410    * @param step Number of running tasks step.
 411    */
 412   private stepWorkerRunningTasks (worker: Worker, step: number): void {
 413     if (this.checkWorkerTasksUsage(worker) === true) {
 414       const tasksUsage = this.workersTasksUsage.get(worker) as TasksUsage
 415       tasksUsage.running = tasksUsage.running + step
 416       this.workersTasksUsage.set(worker, tasksUsage)
 417     }
 418   }
 419
 420   /**
 421    * Steps the number of tasks that the given worker has run.
 422    *
 423    * @param worker Worker which has run tasks.
 424    * @param step Number of run tasks step.
 425    */
 426   private stepWorkerRunTasks (worker: Worker, step: number): void {
 427     if (this.checkWorkerTasksUsage(worker) === true) {
 428       const tasksUsage = this.workersTasksUsage.get(worker) as TasksUsage
 429       tasksUsage.run = tasksUsage.run + step
 430       this.workersTasksUsage.set(worker, tasksUsage)
 431     }
 432   }
 433
 434   /**
 435    * Updates tasks runtime for the given worker.
 436    *
 437    * @param worker Worker which run the task.
 438    * @param taskRunTime Worker task runtime.
 439    */
 440   private updateWorkerTasksRunTime (
 441     worker: Worker,
 442     taskRunTime: number | undefined
 443   ): void {
 444     if (
 445       this.workerChoiceStrategyContext.getWorkerChoiceStrategy()
 446         .requiredStatistics.runTime === true &&
 447       this.checkWorkerTasksUsage(worker) === true
 448     ) {
 449       const tasksUsage = this.workersTasksUsage.get(worker) as TasksUsage
 450       tasksUsage.runTime += taskRunTime ?? 0
 451       if (tasksUsage.run !== 0) {
 452         tasksUsage.avgRunTime = tasksUsage.runTime / tasksUsage.run
 453       }
 454       this.workersTasksUsage.set(worker, tasksUsage)
 455     }
 456   }
 457
 458   /**
 459    * Checks if the given worker is registered in the workers tasks usage map.
 460    *
 461    * @param worker Worker to check.
 462    * @returns `true` if the worker is registered in the workers tasks usage map. `false` otherwise.
 463    */
 464   private checkWorkerTasksUsage (worker: Worker): boolean {
 465     const hasTasksUsage = this.workersTasksUsage.has(worker)
 466     if (hasTasksUsage === false) {
 467       throw new Error('Worker could not be found in workers tasks usage map')
 468     }
 469     return hasTasksUsage
 470   }
 471
 472   /**
 473    * Initializes tasks usage statistics.
 474    *
 475    * @param worker The worker.
 476    */
 477   private initWorkerTasksUsage (worker: Worker): void {
 478     this.workersTasksUsage.set(worker, {
 479       run: 0,
 480       running: 0,
 481       runTime: 0,
 482       avgRunTime: 0
 483     })
 484   }
 485
 486   /**
 487    * Removes worker tasks usage statistics.
 488    *
 489    * @param worker The worker.
 490    */
 491   private removeWorkerTasksUsage (worker: Worker): void {
 492     this.workersTasksUsage.delete(worker)
 493   }
 494
 495   /**
 496    * Resets worker tasks usage statistics.
 497    *
 498    * @param worker The worker.
 499    */
 500   private resetWorkerTasksUsage (worker: Worker): void {
 501     this.removeWorkerTasksUsage(worker)
 502     this.initWorkerTasksUsage(worker)
 503   }
 504 }