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
  77     this.chooseWorker.bind(this)
  78     this.internalExecute.bind(this)
  79     this.checkAndEmitBusy.bind(this)
  80     this.sendToWorker.bind(this)
  81
  82     this.setupHook()
  83
  84     for (let i = 1; i <= this.numberOfWorkers; i++) {
  85       this.createAndSetupWorker()
  86     }
  87
  88     if (this.opts.enableEvents === true) {
  89       this.emitter = new PoolEmitter()
  90     }
  91     this.workerChoiceStrategyContext = new WorkerChoiceStrategyContext(
  92       this,
  93       () => {
  94         const createdWorker = this.createAndSetupWorker()
  95         this.registerWorkerMessageListener(createdWorker, message => {
  96           if (
  97             isKillBehavior(KillBehaviors.HARD, message.kill) ||
  98             this.getWorkerTasksUsage(createdWorker)?.running === 0
  99           ) {
 100             // Kill received from the worker, means that no new tasks are submitted to that worker for a while ( > maxInactiveTime)
 101             void this.destroyWorker(createdWorker)
 102           }
 103         })
 104         return this.getWorkerKey(createdWorker)
 105       },
 106       this.opts.workerChoiceStrategy
 107     )
 108   }
 109
 110   private checkFilePath (filePath: string): void {
 111     if (
 112       filePath == null ||
 113       (typeof filePath === 'string' && filePath.trim().length === 0)
 114     ) {
 115       throw new Error('Please specify a file with a worker implementation')
 116     }
 117   }
 118
 119   private checkNumberOfWorkers (numberOfWorkers: number): void {
 120     if (numberOfWorkers == null) {
 121       throw new Error(
 122         'Cannot instantiate a pool without specifying the number of workers'
 123       )
 124     } else if (!Number.isSafeInteger(numberOfWorkers)) {
 125       throw new TypeError(
 126         'Cannot instantiate a pool with a non integer number of workers'
 127       )
 128     } else if (numberOfWorkers < 0) {
 129       throw new RangeError(
 130         'Cannot instantiate a pool with a negative number of workers'
 131       )
 132     } else if (this.type === PoolType.FIXED && numberOfWorkers === 0) {
 133       throw new Error('Cannot instantiate a fixed pool with no worker')
 134     }
 135   }
 136
 137   private checkPoolOptions (opts: PoolOptions<Worker>): void {
 138     this.opts.workerChoiceStrategy =
 139       opts.workerChoiceStrategy ?? WorkerChoiceStrategies.ROUND_ROBIN
 140     this.opts.enableEvents = opts.enableEvents ?? true
 141   }
 142
 143   /** {@inheritDoc} */
 144   public abstract get type (): PoolType
 145
 146   /** {@inheritDoc} */
 147   public get numberOfRunningTasks (): number {
 148     return this.promiseResponseMap.size
 149   }
 150
 151   /**
 152    * Gets the given worker key.
 153    *
 154    * @param worker - The worker.
 155    * @returns The worker key if the worker is found in the pool, `-1` otherwise.
 156    */
 157   private getWorkerKey (worker: Worker): number {
 158     return this.workers.findIndex(workerItem => workerItem.worker === worker)
 159   }
 160
 161   /** {@inheritDoc} */
 162   public setWorkerChoiceStrategy (
 163     workerChoiceStrategy: WorkerChoiceStrategy
 164   ): void {
 165     this.opts.workerChoiceStrategy = workerChoiceStrategy
 166     for (const [index, workerItem] of this.workers.entries()) {
 167       this.setWorker(index, workerItem.worker, {
 168         run: 0,
 169         running: 0,
 170         runTime: 0,
 171         avgRunTime: 0,
 172         error: 0
 173       })
 174     }
 175     this.workerChoiceStrategyContext.setWorkerChoiceStrategy(
 176       workerChoiceStrategy
 177     )
 178   }
 179
 180   /** {@inheritDoc} */
 181   public abstract get busy (): boolean
 182
 183   protected internalGetBusyStatus (): boolean {
 184     return (
 185       this.numberOfRunningTasks >= this.numberOfWorkers &&
 186       this.findFreeWorkerKey() === -1
 187     )
 188   }
 189
 190   /** {@inheritDoc} */
 191   public findFreeWorkerKey (): number {
 192     return this.workers.findIndex(workerItem => {
 193       return workerItem.tasksUsage.running === 0
 194     })
 195   }
 196
 197   /** {@inheritDoc} */
 198   public async execute (data: Data): Promise<Response> {
 199     const [workerKey, worker] = this.chooseWorker()
 200     const messageId = crypto.randomUUID()
 201     const res = this.internalExecute(workerKey, worker, messageId)
 202     this.checkAndEmitBusy()
 203     this.sendToWorker(worker, {
 204       // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
 205       data: data ?? ({} as Data),
 206       id: messageId
 207     })
 208     // eslint-disable-next-line @typescript-eslint/return-await
 209     return res
 210   }
 211
 212   /** {@inheritDoc} */
 213   public async destroy (): Promise<void> {
 214     await Promise.all(
 215       this.workers.map(async workerItem => {
 216         await this.destroyWorker(workerItem.worker)
 217       })
 218     )
 219   }
 220
 221   /**
 222    * Shutdowns given worker.
 223    *
 224    * @param worker - A worker within `workers`.
 225    */
 226   protected abstract destroyWorker (worker: Worker): void | Promise<void>
 227
 228   /**
 229    * Setup hook that can be overridden by a Poolifier pool implementation
 230    * to run code before workers are created in the abstract constructor.
 231    */
 232   protected setupHook (): void {
 233     // Can be overridden
 234   }
 235
 236   /**
 237    * Should return whether the worker is the main worker or not.
 238    */
 239   protected abstract isMain (): boolean
 240
 241   /**
 242    * Hook executed before the worker task promise resolution.
 243    * Can be overridden.
 244    *
 245    * @param workerKey - The worker key.
 246    */
 247   protected beforePromiseResponseHook (workerKey: number): void {
 248     ++this.workers[workerKey].tasksUsage.running
 249   }
 250
 251   /**
 252    * Hook executed after the worker task promise resolution.
 253    * Can be overridden.
 254    *
 255    * @param worker - The worker.
 256    * @param message - The received message.
 257    */
 258   protected afterPromiseResponseHook (
 259     worker: Worker,
 260     message: MessageValue<Response>
 261   ): void {
 262     const workerTasksUsage = this.getWorkerTasksUsage(worker) as TasksUsage
 263     --workerTasksUsage.running
 264     ++workerTasksUsage.run
 265     if (message.error != null) {
 266       ++workerTasksUsage.error
 267     }
 268     if (this.workerChoiceStrategyContext.getRequiredStatistics().runTime) {
 269       workerTasksUsage.runTime += message.taskRunTime ?? 0
 270       if (
 271         this.workerChoiceStrategyContext.getRequiredStatistics().avgRunTime &&
 272         workerTasksUsage.run !== 0
 273       ) {
 274         workerTasksUsage.avgRunTime =
 275           workerTasksUsage.runTime / workerTasksUsage.run
 276       }
 277     }
 278   }
 279
 280   /**
 281    * Removes the given worker from the pool.
 282    *
 283    * @param worker - The worker that will be removed.
 284    */
 285   protected removeWorker (worker: Worker): void {
 286     const workerKey = this.getWorkerKey(worker)
 287     this.workers.splice(workerKey, 1)
 288     this.workerChoiceStrategyContext.remove(workerKey)
 289   }
 290
 291   /**
 292    * Chooses a worker for the next task.
 293    *
 294    * The default implementation uses a round robin algorithm to distribute the load.
 295    *
 296    * @returns [worker key, worker].
 297    */
 298   protected chooseWorker (): [number, Worker] {
 299     const workerKey = this.workerChoiceStrategyContext.execute()
 300     return [workerKey, this.workers[workerKey].worker]
 301   }
 302
 303   /**
 304    * Sends a message to the given worker.
 305    *
 306    * @param worker - The worker which should receive the message.
 307    * @param message - The message.
 308    */
 309   protected abstract sendToWorker (
 310     worker: Worker,
 311     message: MessageValue<Data>
 312   ): void
 313
 314   /**
 315    * Registers a listener callback on a given worker.
 316    *
 317    * @param worker - The worker which should register a listener.
 318    * @param listener - The message listener callback.
 319    */
 320   protected abstract registerWorkerMessageListener<
 321     Message extends Data | Response
 322   >(worker: Worker, listener: (message: MessageValue<Message>) => void): void
 323
 324   /**
 325    * Returns a newly created worker.
 326    */
 327   protected abstract createWorker (): Worker
 328
 329   /**
 330    * Function that can be hooked up when a worker has been newly created and moved to the workers registry.
 331    *
 332    * Can be used to update the `maxListeners` or binding the `main-worker`\<-\>`worker` connection if not bind by default.
 333    *
 334    * @param worker - The newly created worker.
 335    */
 336   protected abstract afterWorkerSetup (worker: Worker): void
 337
 338   /**
 339    * Creates a new worker for this pool and sets it up completely.
 340    *
 341    * @returns New, completely set up worker.
 342    */
 343   protected createAndSetupWorker (): Worker {
 344     const worker = this.createWorker()
 345
 346     worker.on('message', this.opts.messageHandler ?? EMPTY_FUNCTION)
 347     worker.on('error', this.opts.errorHandler ?? EMPTY_FUNCTION)
 348     worker.on('online', this.opts.onlineHandler ?? EMPTY_FUNCTION)
 349     worker.on('exit', this.opts.exitHandler ?? EMPTY_FUNCTION)
 350     worker.once('exit', () => {
 351       this.removeWorker(worker)
 352     })
 353
 354     this.pushWorker(worker, {
 355       run: 0,
 356       running: 0,
 357       runTime: 0,
 358       avgRunTime: 0,
 359       error: 0
 360     })
 361
 362     this.afterWorkerSetup(worker)
 363
 364     return worker
 365   }
 366
 367   /**
 368    * This function is the listener registered for each worker.
 369    *
 370    * @returns The listener function to execute when a message is received from a worker.
 371    */
 372   protected workerListener (): (message: MessageValue<Response>) => void {
 373     return message => {
 374       if (message.id !== undefined) {
 375         const promiseResponse = this.promiseResponseMap.get(message.id)
 376         if (promiseResponse !== undefined) {
 377           if (message.error != null) {
 378             promiseResponse.reject(message.error)
 379           } else {
 380             promiseResponse.resolve(message.data as Response)
 381           }
 382           this.afterPromiseResponseHook(promiseResponse.worker, message)
 383           this.promiseResponseMap.delete(message.id)
 384         }
 385       }
 386     }
 387   }
 388
 389   private async internalExecute (
 390     workerKey: number,
 391     worker: Worker,
 392     messageId: string
 393   ): Promise<Response> {
 394     this.beforePromiseResponseHook(workerKey)
 395     return await new Promise<Response>((resolve, reject) => {
 396       this.promiseResponseMap.set(messageId, { resolve, reject, worker })
 397     })
 398   }
 399
 400   private checkAndEmitBusy (): void {
 401     if (this.opts.enableEvents === true && this.busy) {
 402       this.emitter?.emit('busy')
 403     }
 404   }
 405
 406   /**
 407    * Gets worker tasks usage.
 408    *
 409    * @param worker - The worker.
 410    * @returns The worker tasks usage.
 411    */
 412   private getWorkerTasksUsage (worker: Worker): TasksUsage | undefined {
 413     const workerKey = this.getWorkerKey(worker)
 414     if (workerKey !== -1) {
 415       return this.workers[workerKey].tasksUsage
 416     }
 417     throw new Error('Worker could not be found in the pool')
 418   }
 419
 420   /**
 421    * Pushes the given worker.
 422    *
 423    * @param worker - The worker.
 424    * @param tasksUsage - The worker tasks usage.
 425    */
 426   private pushWorker (worker: Worker, tasksUsage: TasksUsage): void {
 427     this.workers.push({
 428       worker,
 429       tasksUsage
 430     })
 431   }
 432
 433   /**
 434    * Sets the given worker.
 435    *
 436    * @param workerKey - The worker key.
 437    * @param worker - The worker.
 438    * @param tasksUsage - The worker tasks usage.
 439    */
 440   private setWorker (
 441     workerKey: number,
 442     worker: Worker,
 443     tasksUsage: TasksUsage
 444   ): void {
 445     this.workers[workerKey] = {
 446       worker,
 447       tasksUsage
 448     }
 449   }
 450 }