src/worker/abstract-worker.ts

   1 import { AsyncResource } from 'node:async_hooks'
   2 import type { Worker } from 'node:cluster'
   3 import type { MessagePort } from 'node:worker_threads'
   4 import { performance } from 'node:perf_hooks'
   5 import type {
   6   MessageValue,
   7   TaskPerformance,
   8   WorkerStatistics
   9 } from '../utility-types'
  10 import { EMPTY_FUNCTION, isAsyncFunction, isPlainObject } from '../utils'
  11 import {
  12   type KillBehavior,
  13   KillBehaviors,
  14   type WorkerOptions
  15 } from './worker-options'
  16 import type {
  17   TaskFunctions,
  18   WorkerAsyncFunction,
  19   WorkerFunction,
  20   WorkerSyncFunction
  21 } from './worker-functions'
  22
  23 const DEFAULT_FUNCTION_NAME = 'default'
  24 const DEFAULT_MAX_INACTIVE_TIME = 60000
  25 const DEFAULT_KILL_BEHAVIOR: KillBehavior = KillBehaviors.SOFT
  26
  27 /**
  28  * Base class that implements some shared logic for all poolifier workers.
  29  *
  30  * @typeParam MainWorker - Type of main worker.
  31  * @typeParam Data - Type of data this worker receives from pool's execution. This can only be structured-cloneable data.
  32  * @typeParam Response - Type of response the worker sends back to the main worker. This can only be structured-cloneable data.
  33  */
  34 export abstract class AbstractWorker<
  35   MainWorker extends Worker | MessagePort,
  36   Data = unknown,
  37   Response = unknown
  38 > extends AsyncResource {
  39   /**
  40    * Worker id.
  41    */
  42   protected abstract id: number
  43   /**
  44    * Task function(s) processed by the worker when the pool's `execution` function is invoked.
  45    */
  46   protected taskFunctions!: Map<string, WorkerFunction<Data, Response>>
  47   /**
  48    * Timestamp of the last task processed by this worker.
  49    */
  50   protected lastTaskTimestamp!: number
  51   /**
  52    * Performance statistics computation requirements.
  53    */
  54   protected statistics!: WorkerStatistics
  55   /**
  56    * Handler id of the `aliveInterval` worker alive check.
  57    */
  58   protected aliveInterval?: NodeJS.Timeout
  59   /**
  60    * Constructs a new poolifier worker.
  61    *
  62    * @param type - The type of async event.
  63    * @param isMain - Whether this is the main worker or not.
  64    * @param taskFunctions - Task function(s) processed by the worker when the pool's `execution` function is invoked. The first function is the default function.
  65    * @param mainWorker - Reference to main worker.
  66    * @param opts - Options for the worker.
  67    */
  68   public constructor (
  69     type: string,
  70     protected readonly isMain: boolean,
  71     taskFunctions:
  72     | WorkerFunction<Data, Response>
  73     | TaskFunctions<Data, Response>,
  74     protected readonly mainWorker: MainWorker,
  75     protected readonly opts: WorkerOptions = {
  76       /**
  77        * The kill behavior option on this worker or its default value.
  78        */
  79       killBehavior: DEFAULT_KILL_BEHAVIOR,
  80       /**
  81        * The maximum time to keep this worker alive while idle.
  82        * The pool automatically checks and terminates this worker when the time expires.
  83        */
  84       maxInactiveTime: DEFAULT_MAX_INACTIVE_TIME
  85     }
  86   ) {
  87     super(type)
  88     this.checkWorkerOptions(this.opts)
  89     this.checkTaskFunctions(taskFunctions)
  90     if (!this.isMain) {
  91       this.mainWorker?.on('message', this.messageListener.bind(this))
  92     }
  93   }
  94
  95   private checkWorkerOptions (opts: WorkerOptions): void {
  96     this.opts.killBehavior = opts.killBehavior ?? DEFAULT_KILL_BEHAVIOR
  97     this.opts.maxInactiveTime =
  98       opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME
  99     delete this.opts.async
 100   }
 101
 102   /**
 103    * Checks if the `taskFunctions` parameter is passed to the constructor.
 104    *
 105    * @param taskFunctions - The task function(s) parameter that should be checked.
 106    */
 107   private checkTaskFunctions (
 108     taskFunctions:
 109     | WorkerFunction<Data, Response>
 110     | TaskFunctions<Data, Response>
 111   ): void {
 112     if (taskFunctions == null) {
 113       throw new Error('taskFunctions parameter is mandatory')
 114     }
 115     this.taskFunctions = new Map<string, WorkerFunction<Data, Response>>()
 116     if (typeof taskFunctions === 'function') {
 117       this.taskFunctions.set(DEFAULT_FUNCTION_NAME, taskFunctions.bind(this))
 118     } else if (isPlainObject(taskFunctions)) {
 119       let firstEntry = true
 120       for (const [name, fn] of Object.entries(taskFunctions)) {
 121         if (typeof fn !== 'function') {
 122           throw new TypeError(
 123             'A taskFunctions parameter object value is not a function'
 124           )
 125         }
 126         this.taskFunctions.set(name, fn.bind(this))
 127         if (firstEntry) {
 128           this.taskFunctions.set(DEFAULT_FUNCTION_NAME, fn.bind(this))
 129           firstEntry = false
 130         }
 131       }
 132       if (firstEntry) {
 133         throw new Error('taskFunctions parameter object is empty')
 134       }
 135     } else {
 136       throw new TypeError(
 137         'taskFunctions parameter is not a function or a plain object'
 138       )
 139     }
 140   }
 141
 142   /**
 143    * Worker message listener.
 144    *
 145    * @param message - Message received.
 146    */
 147   protected messageListener (message: MessageValue<Data, Data>): void {
 148     if (message.statistics != null) {
 149       // Statistics message received
 150       this.statistics = message.statistics
 151     } else if (message.checkAlive != null) {
 152       // Check alive message received
 153       message.checkAlive ? this.startCheckAlive() : this.stopCheckAlive()
 154     } else if (message.id != null && message.data != null) {
 155       // Task message received
 156       const fn = this.getTaskFunction(message.name)
 157       if (isAsyncFunction(fn)) {
 158         this.runInAsyncScope(this.runAsync.bind(this), this, fn, message)
 159       } else {
 160         this.runInAsyncScope(this.runSync.bind(this), this, fn, message)
 161       }
 162     } else if (message.kill === true) {
 163       // Kill message received
 164       this.stopCheckAlive()
 165       this.emitDestroy()
 166     }
 167   }
 168
 169   /**
 170    * Starts the worker alive check interval.
 171    */
 172   private startCheckAlive (): void {
 173     this.lastTaskTimestamp = performance.now()
 174     this.aliveInterval = setInterval(
 175       this.checkAlive.bind(this),
 176       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME) / 2
 177     )
 178     this.checkAlive.bind(this)()
 179   }
 180
 181   /**
 182    * Stops the worker alive check interval.
 183    */
 184   private stopCheckAlive (): void {
 185     this.aliveInterval != null && clearInterval(this.aliveInterval)
 186   }
 187
 188   /**
 189    * Checks if the worker should be terminated, because its living too long.
 190    */
 191   private checkAlive (): void {
 192     if (
 193       performance.now() - this.lastTaskTimestamp >
 194       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME)
 195     ) {
 196       this.sendToMainWorker({ kill: this.opts.killBehavior })
 197     }
 198   }
 199
 200   /**
 201    * Returns the main worker.
 202    *
 203    * @returns Reference to the main worker.
 204    */
 205   protected getMainWorker (): MainWorker {
 206     if (this.mainWorker == null) {
 207       throw new Error('Main worker not set')
 208     }
 209     return this.mainWorker
 210   }
 211
 212   /**
 213    * Sends a message to the main worker.
 214    *
 215    * @param message - The response message.
 216    */
 217   protected abstract sendToMainWorker (
 218     message: MessageValue<Response, Data>
 219   ): void
 220
 221   /**
 222    * Handles an error and convert it to a string so it can be sent back to the main worker.
 223    *
 224    * @param e - The error raised by the worker.
 225    * @returns The error message.
 226    */
 227   protected handleError (e: Error | string): string {
 228     return e instanceof Error ? e.message : e
 229   }
 230
 231   /**
 232    * Runs the given function synchronously.
 233    *
 234    * @param fn - Function that will be executed.
 235    * @param message - Input data for the given function.
 236    */
 237   protected runSync (
 238     fn: WorkerSyncFunction<Data, Response>,
 239     message: MessageValue<Data>
 240   ): void {
 241     try {
 242       let taskPerformance = this.beginTaskPerformance()
 243       const res = fn(message.data)
 244       taskPerformance = this.endTaskPerformance(taskPerformance)
 245       this.sendToMainWorker({
 246         data: res,
 247         taskPerformance,
 248         workerId: this.id,
 249         id: message.id
 250       })
 251     } catch (e) {
 252       const errorMessage = this.handleError(e as Error | string)
 253       this.sendToMainWorker({
 254         taskError: {
 255           workerId: this.id,
 256           message: errorMessage,
 257           data: message.data
 258         },
 259         id: message.id
 260       })
 261     } finally {
 262       if (!this.isMain && this.aliveInterval != null) {
 263         this.lastTaskTimestamp = performance.now()
 264       }
 265     }
 266   }
 267
 268   /**
 269    * Runs the given function asynchronously.
 270    *
 271    * @param fn - Function that will be executed.
 272    * @param message - Input data for the given function.
 273    */
 274   protected runAsync (
 275     fn: WorkerAsyncFunction<Data, Response>,
 276     message: MessageValue<Data>
 277   ): void {
 278     let taskPerformance = this.beginTaskPerformance()
 279     fn(message.data)
 280       .then(res => {
 281         taskPerformance = this.endTaskPerformance(taskPerformance)
 282         this.sendToMainWorker({
 283           data: res,
 284           taskPerformance,
 285           workerId: this.id,
 286           id: message.id
 287         })
 288         return null
 289       })
 290       .catch(e => {
 291         const errorMessage = this.handleError(e as Error | string)
 292         this.sendToMainWorker({
 293           taskError: {
 294             workerId: this.id,
 295             message: errorMessage,
 296             data: message.data
 297           },
 298           id: message.id
 299         })
 300       })
 301       .finally(() => {
 302         if (!this.isMain && this.aliveInterval != null) {
 303           this.lastTaskTimestamp = performance.now()
 304         }
 305       })
 306       .catch(EMPTY_FUNCTION)
 307   }
 308
 309   /**
 310    * Gets the task function in the given scope.
 311    *
 312    * @param name - Name of the function that will be returned.
 313    */
 314   private getTaskFunction (name?: string): WorkerFunction<Data, Response> {
 315     name = name ?? DEFAULT_FUNCTION_NAME
 316     const fn = this.taskFunctions.get(name)
 317     if (fn == null) {
 318       throw new Error(`Task function '${name}' not found`)
 319     }
 320     return fn
 321   }
 322
 323   private beginTaskPerformance (): TaskPerformance {
 324     this.checkStatistics()
 325     return {
 326       timestamp: performance.now(),
 327       ...(this.statistics.elu && { elu: performance.eventLoopUtilization() })
 328     }
 329   }
 330
 331   private endTaskPerformance (
 332     taskPerformance: TaskPerformance
 333   ): TaskPerformance {
 334     this.checkStatistics()
 335     return {
 336       ...taskPerformance,
 337       ...(this.statistics.runTime && {
 338         runTime: performance.now() - taskPerformance.timestamp
 339       }),
 340       ...(this.statistics.elu && {
 341         elu: performance.eventLoopUtilization(taskPerformance.elu)
 342       })
 343     }
 344   }
 345
 346   private checkStatistics (): void {
 347     if (this.statistics == null) {
 348       throw new Error('Performance statistics computation requirements not set')
 349     }
 350   }
 351 }