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.workerId === this.id) {
 149       if (message.ready != null) {
 150         // Startup message received
 151         this.workerReady()
 152       } else if (message.statistics != null) {
 153         // Statistics message received
 154         this.statistics = message.statistics
 155       } else if (message.checkAlive != null) {
 156         // Check alive message received
 157         message.checkAlive ? this.startCheckAlive() : this.stopCheckAlive()
 158       } else if (message.id != null && message.data != null) {
 159         // Task message received
 160         const fn = this.getTaskFunction(message.name)
 161         if (isAsyncFunction(fn)) {
 162           this.runInAsyncScope(this.runAsync.bind(this), this, fn, message)
 163         } else {
 164           this.runInAsyncScope(this.runSync.bind(this), this, fn, message)
 165         }
 166       } else if (message.kill === true) {
 167         // Kill message received
 168         this.stopCheckAlive()
 169         this.emitDestroy()
 170       }
 171     }
 172   }
 173
 174   /**
 175    * Notifies the main worker that this worker is ready to process tasks.
 176    */
 177   protected workerReady (): void {
 178     !this.isMain && this.sendToMainWorker({ ready: true, workerId: this.id })
 179   }
 180
 181   /**
 182    * Starts the worker alive check interval.
 183    */
 184   private startCheckAlive (): void {
 185     this.lastTaskTimestamp = performance.now()
 186     this.aliveInterval = setInterval(
 187       this.checkAlive.bind(this),
 188       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME) / 2
 189     )
 190     this.checkAlive.bind(this)()
 191   }
 192
 193   /**
 194    * Stops the worker alive check interval.
 195    */
 196   private stopCheckAlive (): void {
 197     this.aliveInterval != null && clearInterval(this.aliveInterval)
 198   }
 199
 200   /**
 201    * Checks if the worker should be terminated, because its living too long.
 202    */
 203   private checkAlive (): void {
 204     if (
 205       performance.now() - this.lastTaskTimestamp >
 206       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME)
 207     ) {
 208       this.sendToMainWorker({ kill: this.opts.killBehavior, workerId: this.id })
 209     }
 210   }
 211
 212   /**
 213    * Returns the main worker.
 214    *
 215    * @returns Reference to the main worker.
 216    */
 217   protected getMainWorker (): MainWorker {
 218     if (this.mainWorker == null) {
 219       throw new Error('Main worker not set')
 220     }
 221     return this.mainWorker
 222   }
 223
 224   /**
 225    * Sends a message to the main worker.
 226    *
 227    * @param message - The response message.
 228    */
 229   protected abstract sendToMainWorker (
 230     message: MessageValue<Response, Data>
 231   ): void
 232
 233   /**
 234    * Handles an error and convert it to a string so it can be sent back to the main worker.
 235    *
 236    * @param e - The error raised by the worker.
 237    * @returns The error message.
 238    */
 239   protected handleError (e: Error | string): string {
 240     return e instanceof Error ? e.message : e
 241   }
 242
 243   /**
 244    * Runs the given function synchronously.
 245    *
 246    * @param fn - Function that will be executed.
 247    * @param message - Input data for the given function.
 248    */
 249   protected runSync (
 250     fn: WorkerSyncFunction<Data, Response>,
 251     message: MessageValue<Data>
 252   ): void {
 253     try {
 254       let taskPerformance = this.beginTaskPerformance()
 255       const res = fn(message.data)
 256       taskPerformance = this.endTaskPerformance(taskPerformance)
 257       this.sendToMainWorker({
 258         data: res,
 259         taskPerformance,
 260         workerId: this.id,
 261         id: message.id
 262       })
 263     } catch (e) {
 264       const errorMessage = this.handleError(e as Error | string)
 265       this.sendToMainWorker({
 266         taskError: {
 267           message: errorMessage,
 268           data: message.data
 269         },
 270         workerId: this.id,
 271         id: message.id
 272       })
 273     } finally {
 274       if (!this.isMain && this.aliveInterval != null) {
 275         this.lastTaskTimestamp = performance.now()
 276       }
 277     }
 278   }
 279
 280   /**
 281    * Runs the given function asynchronously.
 282    *
 283    * @param fn - Function that will be executed.
 284    * @param message - Input data for the given function.
 285    */
 286   protected runAsync (
 287     fn: WorkerAsyncFunction<Data, Response>,
 288     message: MessageValue<Data>
 289   ): void {
 290     let taskPerformance = this.beginTaskPerformance()
 291     fn(message.data)
 292       .then(res => {
 293         taskPerformance = this.endTaskPerformance(taskPerformance)
 294         this.sendToMainWorker({
 295           data: res,
 296           taskPerformance,
 297           workerId: this.id,
 298           id: message.id
 299         })
 300         return null
 301       })
 302       .catch(e => {
 303         const errorMessage = this.handleError(e as Error | string)
 304         this.sendToMainWorker({
 305           taskError: {
 306             message: errorMessage,
 307             data: message.data
 308           },
 309           workerId: this.id,
 310           id: message.id
 311         })
 312       })
 313       .finally(() => {
 314         if (!this.isMain && this.aliveInterval != null) {
 315           this.lastTaskTimestamp = performance.now()
 316         }
 317       })
 318       .catch(EMPTY_FUNCTION)
 319   }
 320
 321   /**
 322    * Gets the task function in the given scope.
 323    *
 324    * @param name - Name of the function that will be returned.
 325    */
 326   private getTaskFunction (name?: string): WorkerFunction<Data, Response> {
 327     name = name ?? DEFAULT_FUNCTION_NAME
 328     const fn = this.taskFunctions.get(name)
 329     if (fn == null) {
 330       throw new Error(`Task function '${name}' not found`)
 331     }
 332     return fn
 333   }
 334
 335   private beginTaskPerformance (): TaskPerformance {
 336     this.checkStatistics()
 337     return {
 338       timestamp: performance.now(),
 339       ...(this.statistics.elu && { elu: performance.eventLoopUtilization() })
 340     }
 341   }
 342
 343   private endTaskPerformance (
 344     taskPerformance: TaskPerformance
 345   ): TaskPerformance {
 346     this.checkStatistics()
 347     return {
 348       ...taskPerformance,
 349       ...(this.statistics.runTime && {
 350         runTime: performance.now() - taskPerformance.timestamp
 351       }),
 352       ...(this.statistics.elu && {
 353         elu: performance.eventLoopUtilization(taskPerformance.elu)
 354       })
 355     }
 356   }
 357
 358   private checkStatistics (): void {
 359     if (this.statistics == null) {
 360       throw new Error('Performance statistics computation requirements not set')
 361     }
 362   }
 363 }