src/pools/abstract-pool.ts

   1 import crypto from 'node:crypto'
   2 import type {
   3   MessageValue,
   4   PromiseWorkerResponseWrapper
   5 } from '../utility-types'
   6 import { EMPTY_FUNCTION } from '../utils'
   7 import { KillBehaviors, isKillBehavior } from '../worker/worker-options'
   8 import type { PoolOptions } from './pool'
   9 import { PoolEmitter } from './pool'
  10 import type { IPoolInternal, TasksUsage, WorkerType } from './pool-internal'
  11 import { PoolType } from './pool-internal'
  12 import type { IPoolWorker } from './pool-worker'
  13 import {
  14   WorkerChoiceStrategies,
  15   type WorkerChoiceStrategy
  16 } from './selection-strategies/selection-strategies-types'
  17 import { WorkerChoiceStrategyContext } from './selection-strategies/worker-choice-strategy-context'
  18
  19 /**
  20  * Base class that implements some shared logic for all poolifier pools.
  21  *
  22  * @typeParam Worker - Type of worker which manages this pool.
  23  * @typeParam Data - Type of data sent to the worker. This can only be serializable data.
  24  * @typeParam Response - Type of response of execution. This can only be serializable data.
  25  */
  26 export abstract class AbstractPool<
  27   Worker extends IPoolWorker,
  28   Data = unknown,
  29   Response = unknown
  30 > implements IPoolInternal<Worker, Data, Response> {
  31   /** {@inheritDoc} */
  32   public readonly workers: Map<number, WorkerType<Worker>> = new Map<
  33   number,
  34   WorkerType<Worker>
  35   >()
  36
  37   /** {@inheritDoc} */
  38   public readonly emitter?: PoolEmitter
  39
  40   /**
  41    * Id of the next worker.
  42    */
  43   protected nextWorkerId: number = 0
  44
  45   /**
  46    * The promise map.
  47    *
  48    * - `key`: This is the message id of each submitted task.
  49    * - `value`: An object that contains the worker, the resolve function and the reject function.
  50    *
  51    * When we receive a message from the worker we get a map entry and resolve/reject the promise based on the message.
  52    */
  53   protected promiseMap: Map<
  54   string,
  55   PromiseWorkerResponseWrapper<Worker, Response>
  56   > = new Map<string, PromiseWorkerResponseWrapper<Worker, Response>>()
  57
  58   /**
  59    * Worker choice strategy instance implementing the worker choice algorithm.
  60    *
  61    * Default to a strategy implementing a round robin algorithm.
  62    */
  63   protected workerChoiceStrategyContext: WorkerChoiceStrategyContext<
  64   Worker,
  65   Data,
  66   Response
  67   >
  68
  69   /**
  70    * Constructs a new poolifier pool.
  71    *
  72    * @param numberOfWorkers - Number of workers that this pool should manage.
  73    * @param filePath - Path to the worker-file.
  74    * @param opts - Options for the pool.
  75    */
  76   public constructor (
  77     public readonly numberOfWorkers: number,
  78     public readonly filePath: string,
  79     public readonly opts: PoolOptions<Worker>
  80   ) {
  81     if (!this.isMain()) {
  82       throw new Error('Cannot start a pool from a worker!')
  83     }
  84     this.checkNumberOfWorkers(this.numberOfWorkers)
  85     this.checkFilePath(this.filePath)
  86     this.checkPoolOptions(this.opts)
  87     this.setupHook()
  88
  89     for (let i = 1; i <= this.numberOfWorkers; i++) {
  90       this.createAndSetupWorker()
  91     }
  92
  93     if (this.opts.enableEvents === true) {
  94       this.emitter = new PoolEmitter()
  95     }
  96     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext(
  97       this,
  98       () => {
  99         const workerCreated = this.createAndSetupWorker()
 100         this.registerWorkerMessageListener(workerCreated, message => {
 101           if (
 102             isKillBehavior(KillBehaviors.HARD, message.kill) ||
 103             this.getWorkerTasksUsage(workerCreated)?.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(workerCreated)
 107           }
 108         })
 109         return workerCreated
 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   /** {@inheritDoc} */
 152   public get numberOfRunningTasks (): number {
 153     return this.promiseMap.size
 154   }
 155
 156   /**
 157    * Gets the given worker key.
 158    *
 159    * @param worker - The worker.
 160    * @returns The worker key.
 161    */
 162   private getWorkerKey (worker: Worker): number | undefined {
 163     return [...this.workers].find(([, value]) => value.worker === worker)?.[0]
 164   }
 165
 166   /** {@inheritDoc} */
 167   public setWorkerChoiceStrategy (
 168     workerChoiceStrategy: WorkerChoiceStrategy
 169   ): void {
 170     this.opts.workerChoiceStrategy = workerChoiceStrategy
 171     for (const [key, value] of this.workers) {
 172       this.setWorker(key, value.worker, {
 173         run: 0,
 174         running: 0,
 175         runTime: 0,
 176         avgRunTime: 0
 177       })
 178     }
 179     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 180       workerChoiceStrategy
 181     )
 182   }
 183
 184   /** {@inheritDoc} */
 185   public abstract get busy (): boolean
 186
 187   protected internalGetBusyStatus (): boolean {
 188     return (
 189       this.numberOfRunningTasks >= this.numberOfWorkers &&
 190       this.findFreeWorker() === false
 191     )
 192   }
 193
 194   /** {@inheritDoc} */
 195   public findFreeWorker (): Worker | false {
 196     for (const value of this.workers.values()) {
 197       if (value.tasksUsage.running === 0) {
 198         // A worker is free, return the matching worker
 199         return value.worker
 200       }
 201     }
 202     return false
 203   }
 204
 205   /** {@inheritDoc} */
 206   public async execute (data: Data): Promise<Response> {
 207     const worker = this.chooseWorker()
 208     const messageId = crypto.randomUUID()
 209     const res = this.internalExecute(worker, messageId)
 210     this.checkAndEmitBusy()
 211     this.sendToWorker(worker, {
 212       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 213       data: data ?? ({} as Data),
 214       id: messageId
 215     })
 216     // eslint-disable-next-line @typescript-eslint/return-await
 217     return res
 218   }
 219
 220   /** {@inheritDoc} */
 221   public async destroy (): Promise<void> {
 222     await Promise.all(
 223       [...this.workers].map(async ([, value]) => {
 224         await this.destroyWorker(value.worker)
 225       })
 226     )
 227   }
 228
 229   /**
 230    * Shutdowns given worker.
 231    *
 232    * @param worker - A worker within `workers`.
 233    */
 234   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 235
 236   /**
 237    * Setup hook that can be overridden by a Poolifier pool implementation
 238    * to run code before workers are created in the abstract constructor.
 239    */
 240   protected setupHook (): void {
 241     // Can be overridden
 242   }
 243
 244   /**
 245    * Should return whether the worker is the main worker or not.
 246    */
 247   protected abstract isMain (): boolean
 248
 249   /**
 250    * Hook executed before the worker task promise resolution.
 251    * Can be overridden.
 252    *
 253    * @param worker - The worker.
 254    */
 255   protected beforePromiseWorkerResponseHook (worker: Worker): void {
 256     ++(this.getWorkerTasksUsage(worker) as TasksUsage).running
 257   }
 258
 259   /**
 260    * Hook executed after the worker task promise resolution.
 261    * Can be overridden.
 262    *
 263    * @param message - The received message.
 264    * @param promise - The Promise response.
 265    */
 266   protected afterPromiseWorkerResponseHook (
 267     message: MessageValue<Response>,
 268     promise: PromiseWorkerResponseWrapper<Worker, Response>
 269   ): void {
 270     const workerTasksUsage = this.getWorkerTasksUsage(
 271       promise.worker
 272     ) as TasksUsage
 273     --workerTasksUsage.running
 274     ++workerTasksUsage.run
 275     if (
 276       this.workerChoiceStrategyContext.getWorkerChoiceStrategy()
 277         .requiredStatistics.runTime
 278     ) {
 279       workerTasksUsage.runTime += message.taskRunTime ?? 0
 280       if (workerTasksUsage.run !== 0) {
 281         workerTasksUsage.avgRunTime =
 282           workerTasksUsage.runTime / workerTasksUsage.run
 283       }
 284     }
 285   }
 286
 287   /**
 288    * Removes the given worker from the pool.
 289    *
 290    * @param worker - The worker that will be removed.
 291    */
 292   protected removeWorker (worker: Worker): void {
 293     this.workers.delete(this.getWorkerKey(worker) as number)
 294     --this.nextWorkerId
 295   }
 296
 297   /**
 298    * Chooses a worker for the next task.
 299    *
 300    * The default implementation uses a round robin algorithm to distribute the load.
 301    *
 302    * @returns Worker.
 303    */
 304   protected chooseWorker (): Worker {
 305     return this.workerChoiceStrategyContext.execute()
 306   }
 307
 308   /**
 309    * Sends a message to the given worker.
 310    *
 311    * @param worker - The worker which should receive the message.
 312    * @param message - The message.
 313    */
 314   protected abstract sendToWorker (
 315     worker: Worker,
 316     message: MessageValue<Data>
 317   ): void
 318
 319   /**
 320    * Registers a listener callback on a given worker.
 321    *
 322    * @param worker - The worker which should register a listener.
 323    * @param listener - The message listener callback.
 324    */
 325   protected abstract registerWorkerMessageListener<
 326     Message extends Data | Response
 327   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 328
 329   /**
 330    * Returns a newly created worker.
 331    */
 332   protected abstract createWorker (): Worker
 333
 334   /**
 335    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 336    *
 337    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 338    *
 339    * @param worker - The newly created worker.
 340    */
 341   protected abstract afterWorkerSetup (worker: Worker): void
 342
 343   /**
 344    * Creates a new worker for this pool and sets it up completely.
 345    *
 346    * @returns New, completely set up worker.
 347    */
 348   protected createAndSetupWorker (): Worker {
 349     const worker = this.createWorker()
 350
 351     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 352     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 353     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 354     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 355     worker.once('exit', () => {
 356       this.removeWorker(worker)
 357     })
 358
 359     this.setWorker(this.nextWorkerId, worker, {
 360       run: 0,
 361       running: 0,
 362       runTime: 0,
 363       avgRunTime: 0
 364     })
 365     ++this.nextWorkerId
 366
 367     this.afterWorkerSetup(worker)
 368
 369     return worker
 370   }
 371
 372   /**
 373    * This function is the listener registered for each worker.
 374    *
 375    * @returns The listener function to execute when a message is received from a worker.
 376    */
 377   protected workerListener (): (message: MessageValue<Response>) => void {
 378     return message => {
 379       if (message.id !== undefined) {
 380         const promise = this.promiseMap.get(message.id)
 381         if (promise !== undefined) {
 382           if (message.error != null) {
 383             promise.reject(message.error)
 384           } else {
 385             promise.resolve(message.data as Response)
 386           }
 387           this.afterPromiseWorkerResponseHook(message, promise)
 388           this.promiseMap.delete(message.id)
 389         }
 390       }
 391     }
 392   }
 393
 394   private async internalExecute (
 395     worker: Worker,
 396     messageId: string
 397   ): Promise<Response> {
 398     this.beforePromiseWorkerResponseHook(worker)
 399     return await new Promise<Response>((resolve, reject) => {
 400       this.promiseMap.set(messageId, { resolve, reject, worker })
 401     })
 402   }
 403
 404   private checkAndEmitBusy (): void {
 405     if (this.opts.enableEvents === true && this.busy) {
 406       this.emitter?.emit('busy')
 407     }
 408   }
 409
 410   /** {@inheritDoc} */
 411   public getWorkerTasksUsage (worker: Worker): TasksUsage | undefined {
 412     const workerKey = this.getWorkerKey(worker)
 413     if (workerKey !== undefined) {
 414       const workerEntry = this.workers.get(workerKey) as WorkerType<Worker>
 415       return workerEntry.tasksUsage
 416     }
 417     throw new Error('Worker could not be found in the pool')
 418   }
 419
 420   /**
 421    * Sets the given worker.
 422    *
 423    * @param workerKey - The worker key.
 424    * @param worker - The worker.
 425    * @param tasksUsage - The worker tasks usage.
 426    */
 427   private setWorker (
 428     workerKey: number,
 429     worker: Worker,
 430     tasksUsage: TasksUsage
 431   ): void {
 432     this.workers.set(workerKey, {
 433       worker,
 434       tasksUsage
 435     })
 436   }
 437 }