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 type { IPoolInternal, TasksUsage } from './pool-internal'
   9 import { PoolEmitter, PoolType } from './pool-internal'
  10 import type { IPoolWorker } from './pool-worker'
  11 import {
  12   WorkerChoiceStrategies,
  13   WorkerChoiceStrategy
  14 } from './selection-strategies/selection-strategies-types'
  15 import { WorkerChoiceStrategyContext } from './selection-strategies/worker-choice-strategy-context'
  16
  17 const WORKER_NOT_FOUND_TASKS_USAGE_MAP =
  18   'Worker could not be found in worker tasks usage map'
  19
  20 /**
  21  * Base class that implements some shared logic for all poolifier pools.
  22  *
  23  * @template Worker Type of worker which manages this pool.
  24  * @template Data Type of data sent to the worker. This can only be serializable data.
  25  * @template Response Type of response of execution. This can only be serializable data.
  26  */
  27 export abstract class AbstractPool<
  28   Worker extends IPoolWorker,
  29   Data = unknown,
  30   Response = unknown
  31 > implements IPoolInternal<Worker, Data, Response> {
  32   /** @inheritDoc */
  33   public readonly workers: Worker[] = []
  34
  35   /** @inheritDoc */
  36   public readonly workersTasksUsage: Map<Worker, TasksUsage> = new Map<
  37     Worker,
  38     TasksUsage
  39   >()
  40
  41   /** @inheritDoc */
  42   public readonly emitter?: PoolEmitter
  43
  44   /** @inheritDoc */
  45   public readonly max?: number
  46
  47   /**
  48    * The promise map.
  49    *
  50    * - `key`: This is the message Id of each submitted task.
  51    * - `value`: An object that contains the worker, the resolve function and the reject function.
  52    *
  53    * When we receive a message from the worker we get a map entry and resolve/reject the promise based on the message.
  54    */
  55   protected promiseMap: Map<
  56     number,
  57     PromiseWorkerResponseWrapper<Worker, Response>
  58   > = new Map<number, PromiseWorkerResponseWrapper<Worker, Response>>()
  59
  60   /**
  61    * Id of the next message.
  62    */
  63   protected nextMessageId: number = 0
  64
  65   /**
  66    * Worker choice strategy instance implementing the worker choice algorithm.
  67    *
  68    * Default to a strategy implementing a round robin algorithm.
  69    */
  70   protected workerChoiceStrategyContext: WorkerChoiceStrategyContext<
  71     Worker,
  72     Data,
  73     Response
  74   >
  75
  76   /**
  77    * Constructs a new poolifier pool.
  78    *
  79    * @param numberOfWorkers Number of workers that this pool should manage.
  80    * @param filePath Path to the worker-file.
  81    * @param opts Options for the pool.
  82    */
  83   public constructor (
  84     public readonly numberOfWorkers: number,
  85     public readonly filePath: string,
  86     public readonly opts: PoolOptions<Worker>
  87   ) {
  88     if (!this.isMain()) {
  89       throw new Error('Cannot start a pool from a worker!')
  90     }
  91     this.checkNumberOfWorkers(this.numberOfWorkers)
  92     this.checkFilePath(this.filePath)
  93     this.checkPoolOptions(this.opts)
  94     this.setupHook()
  95
  96     for (let i = 1; i <= this.numberOfWorkers; i++) {
  97       this.createAndSetupWorker()
  98     }
  99
 100     if (this.opts.enableEvents) {
 101       this.emitter = new PoolEmitter()
 102     }
 103     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext(
 104       this,
 105       () => {
 106         const workerCreated = this.createAndSetupWorker()
 107         this.registerWorkerMessageListener(workerCreated, message => {
 108           if (
 109             isKillBehavior(KillBehaviors.HARD, message.kill) ||
 110             this.getWorkerRunningTasks(workerCreated) === 0
 111           ) {
 112             // Kill received from the worker, means that no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 113             this.destroyWorker(workerCreated) as void
 114           }
 115         })
 116         return workerCreated
 117       },
 118       this.opts.workerChoiceStrategy
 119     )
 120   }
 121
 122   private checkFilePath (filePath: string): void {
 123     if (!filePath) {
 124       throw new Error('Please specify a file with a worker implementation')
 125     }
 126   }
 127
 128   private checkNumberOfWorkers (numberOfWorkers: number): void {
 129     if (numberOfWorkers == null) {
 130       throw new Error(
 131         'Cannot instantiate a pool without specifying the number of workers'
 132       )
 133     } else if (Number.isSafeInteger(numberOfWorkers) === false) {
 134       throw new Error(
 135         'Cannot instantiate a pool with a non integer number of workers'
 136       )
 137     } else if (numberOfWorkers < 0) {
 138       throw new Error(
 139         'Cannot instantiate a pool with a negative number of workers'
 140       )
 141     } else if (this.type === PoolType.FIXED && numberOfWorkers === 0) {
 142       throw new Error('Cannot instantiate a fixed pool with no worker')
 143     }
 144   }
 145
 146   private checkPoolOptions (opts: PoolOptions<Worker>): void {
 147     this.opts.workerChoiceStrategy =
 148       opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
 149     this.opts.enableEvents = opts.enableEvents ?? true
 150   }
 151
 152   /** @inheritDoc */
 153   public abstract get type (): PoolType
 154
 155   /** @inheritDoc */
 156   public get numberOfRunningTasks (): number {
 157     return this.promiseMap.size
 158   }
 159
 160   /** @inheritDoc */
 161   public getWorkerIndex (worker: Worker): number {
 162     return this.workers.indexOf(worker)
 163   }
 164
 165   /** @inheritDoc */
 166   public getWorkerRunningTasks (worker: Worker): number | undefined {
 167     return this.workersTasksUsage.get(worker)?.running
 168   }
 169
 170   /** @inheritDoc */
 171   public getWorkerAverageTasksRunTime (worker: Worker): number | undefined {
 172     return this.workersTasksUsage.get(worker)?.avgRunTime
 173   }
 174
 175   /** @inheritDoc */
 176   public setWorkerChoiceStrategy (
 177     workerChoiceStrategy: WorkerChoiceStrategy
 178   ): void {
 179     this.opts.workerChoiceStrategy = workerChoiceStrategy
 180     for (const worker of this.workers) {
 181       this.resetWorkerTasksUsage(worker)
 182     }
 183     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 184       workerChoiceStrategy
 185     )
 186   }
 187
 188   /** @inheritDoc */
 189   public abstract get busy (): boolean
 190
 191   protected internalGetBusyStatus (): boolean {
 192     return (
 193       this.numberOfRunningTasks >= this.numberOfWorkers &&
 194       this.findFreeWorker() === false
 195     )
 196   }
 197
 198   /** @inheritDoc */
 199   public findFreeWorker (): Worker | false {
 200     for (const worker of this.workers) {
 201       if (this.getWorkerRunningTasks(worker) === 0) {
 202         // A worker is free, return the matching worker
 203         return worker
 204       }
 205     }
 206     return false
 207   }
 208
 209   /** @inheritDoc */
 210   public execute (data: Data): Promise<Response> {
 211     // Configure worker to handle message with the specified task
 212     const worker = this.chooseWorker()
 213     const messageId = ++this.nextMessageId
 214     const res = this.internalExecute(worker, messageId)
 215     this.checkAndEmitBusy()
 216     data = data ?? ({} as Data)
 217     this.sendToWorker(worker, { data, id: messageId })
 218     return res
 219   }
 220
 221   /** @inheritDoc */
 222   public async destroy (): Promise<void> {
 223     await Promise.all(this.workers.map(worker => this.destroyWorker(worker)))
 224   }
 225
 226   /**
 227    * Shutdowns given worker.
 228    *
 229    * @param worker A worker within `workers`.
 230    */
 231   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 232
 233   /**
 234    * Setup hook that can be overridden by a Poolifier pool implementation
 235    * to run code before workers are created in the abstract constructor.
 236    */
 237   protected setupHook (): void {
 238     // Can be overridden
 239   }
 240
 241   /**
 242    * Should return whether the worker is the main worker or not.
 243    */
 244   protected abstract isMain (): boolean
 245
 246   /**
 247    * Hook executed before the worker task promise resolution.
 248    * Can be overridden.
 249    *
 250    * @param worker The worker.
 251    */
 252   protected beforePromiseWorkerResponseHook (worker: Worker): void {
 253     this.increaseWorkerRunningTasks(worker)
 254   }
 255
 256   /**
 257    * Hook executed after the worker task promise resolution.
 258    * Can be overridden.
 259    *
 260    * @param message The received message.
 261    * @param promise The Promise response.
 262    */
 263   protected afterPromiseWorkerResponseHook (
 264     message: MessageValue<Response>,
 265     promise: PromiseWorkerResponseWrapper<Worker, Response>
 266   ): void {
 267     this.decreaseWorkerRunningTasks(promise.worker)
 268     this.stepWorkerRunTasks(promise.worker, 1)
 269     this.updateWorkerTasksRunTime(promise.worker, message.taskRunTime)
 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     // Clean worker from data structure
 279     this.workers.splice(this.getWorkerIndex(worker), 1)
 280     this.removeWorkerTasksUsage(worker)
 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.
 289    */
 290   protected chooseWorker (): Worker {
 291     return this.workerChoiceStrategyContext.execute()
 292   }
 293
 294   /**
 295    * Sends a message to the given worker.
 296    *
 297    * @param worker The worker which should receive the message.
 298    * @param message The message.
 299    */
 300   protected abstract sendToWorker (
 301     worker: Worker,
 302     message: MessageValue<Data>
 303   ): void
 304
 305   /**
 306    * Registers a listener callback on a given worker.
 307    *
 308    * @param worker The worker which should register a listener.
 309    * @param listener The message listener callback.
 310    */
 311   protected abstract registerWorkerMessageListener<
 312     Message extends Data | Response
 313   > (worker: Worker, listener: (message: MessageValue<Message>) => void): void
 314
 315   protected internalExecute (
 316     worker: Worker,
 317     messageId: number
 318   ): Promise<Response> {
 319     this.beforePromiseWorkerResponseHook(worker)
 320     return new Promise<Response>((resolve, reject) => {
 321       this.promiseMap.set(messageId, { resolve, reject, worker })
 322     })
 323   }
 324
 325   /**
 326    * Returns a newly created worker.
 327    */
 328   protected abstract createWorker (): Worker
 329
 330   /**
 331    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 332    *
 333    * Can be used to update the `maxListeners` or binding the `main-worker`<->`worker` connection if not bind by default.
 334    *
 335    * @param worker The newly created worker.
 336    */
 337   protected abstract afterWorkerSetup (worker: Worker): void
 338
 339   /**
 340    * Creates a new worker for this pool and sets it up completely.
 341    *
 342    * @returns New, completely set up worker.
 343    */
 344   protected createAndSetupWorker (): Worker {
 345     const worker = this.createWorker()
 346
 347     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 348     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 349     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 350     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 351     worker.once('exit', () => this.removeWorker(worker))
 352
 353     this.workers.push(worker)
 354
 355     // Init worker tasks usage map
 356     this.initWorkerTasksUsage(worker)
 357
 358     this.afterWorkerSetup(worker)
 359
 360     return worker
 361   }
 362
 363   /**
 364    * This function is the listener registered for each worker.
 365    *
 366    * @returns The listener function to execute when a message is received from a worker.
 367    */
 368   protected workerListener (): (message: MessageValue<Response>) => void {
 369     return message => {
 370       if (message.id !== undefined) {
 371         const promise = this.promiseMap.get(message.id)
 372         if (promise !== undefined) {
 373           this.afterPromiseWorkerResponseHook(message, promise)
 374           if (message.error) promise.reject(message.error)
 375           else promise.resolve(message.data as Response)
 376           this.promiseMap.delete(message.id)
 377         }
 378       }
 379     }
 380   }
 381
 382   private checkAndEmitBusy (): void {
 383     if (this.opts.enableEvents && this.busy) {
 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     const tasksUsage = this.workersTasksUsage.get(worker)
 414     if (tasksUsage !== undefined) {
 415       tasksUsage.running = tasksUsage.running + step
 416       this.workersTasksUsage.set(worker, tasksUsage)
 417     } else {
 418       throw new Error(WORKER_NOT_FOUND_TASKS_USAGE_MAP)
 419     }
 420   }
 421
 422   /**
 423    * Steps the number of tasks that the given worker has run.
 424    *
 425    * @param worker Worker which has run tasks.
 426    * @param step Number of run tasks step.
 427    */
 428   private stepWorkerRunTasks (worker: Worker, step: number): void {
 429     const tasksUsage = this.workersTasksUsage.get(worker)
 430     if (tasksUsage !== undefined) {
 431       tasksUsage.run = tasksUsage.run + step
 432       this.workersTasksUsage.set(worker, tasksUsage)
 433     } else {
 434       throw new Error(WORKER_NOT_FOUND_TASKS_USAGE_MAP)
 435     }
 436   }
 437
 438   /**
 439    * Updates tasks runtime for the given worker.
 440    *
 441    * @param worker Worker which run the task.
 442    * @param taskRunTime Worker task runtime.
 443    */
 444   private updateWorkerTasksRunTime (
 445     worker: Worker,
 446     taskRunTime: number | undefined
 447   ): void {
 448     if (
 449       this.workerChoiceStrategyContext.getWorkerChoiceStrategy()
 450         .requiredStatistics.runTime === true
 451     ) {
 452       const tasksUsage = this.workersTasksUsage.get(worker)
 453       if (tasksUsage !== undefined) {
 454         tasksUsage.runTime += taskRunTime ?? 0
 455         if (tasksUsage.run !== 0) {
 456           tasksUsage.avgRunTime = tasksUsage.runTime / tasksUsage.run
 457         }
 458         this.workersTasksUsage.set(worker, tasksUsage)
 459       } else {
 460         throw new Error(WORKER_NOT_FOUND_TASKS_USAGE_MAP)
 461       }
 462     }
 463   }
 464
 465   /**
 466    * Initializes tasks usage statistics.
 467    *
 468    * @param worker The worker.
 469    */
 470   initWorkerTasksUsage (worker: Worker): void {
 471     this.workersTasksUsage.set(worker, {
 472       run: 0,
 473       running: 0,
 474       runTime: 0,
 475       avgRunTime: 0
 476     })
 477   }
 478
 479   /**
 480    * Removes worker tasks usage statistics.
 481    *
 482    * @param worker The worker.
 483    */
 484   private removeWorkerTasksUsage (worker: Worker): void {
 485     this.workersTasksUsage.delete(worker)
 486   }
 487
 488   /**
 489    * Resets worker tasks usage statistics.
 490    *
 491    * @param worker The worker.
 492    */
 493   private resetWorkerTasksUsage (worker: Worker): void {
 494     this.removeWorkerTasksUsage(worker)
 495     this.initWorkerTasksUsage(worker)
 496   }
 497 }