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 type { MessageValue } from '../utility-types'
   5 import { EMPTY_FUNCTION } from '../utils'
   6 import type { KillBehavior, WorkerOptions } from './worker-options'
   7 import { KillBehaviors } from './worker-options'
   8
   9 const DEFAULT_MAX_INACTIVE_TIME = 60000
  10 const DEFAULT_KILL_BEHAVIOR: KillBehavior = KillBehaviors.SOFT
  11
  12 /**
  13  * Base class that implements some shared logic for all poolifier workers.
  14  *
  15  * @typeParam MainWorker - Type of main worker.
  16  * @typeParam Data - Type of data this worker receives from pool's execution. This can only be serializable data.
  17  * @typeParam Response - Type of response the worker sends back to the main worker. This can only be serializable data.
  18  */
  19 export abstract class AbstractWorker<
  20   MainWorker extends Worker | MessagePort,
  21   Data = unknown,
  22   Response = unknown
  23 > extends AsyncResource {
  24   /**
  25    * Timestamp of the last task processed by this worker.
  26    */
  27   protected lastTaskTimestamp!: number
  28   /**
  29    * Handler id of the `aliveInterval` worker alive check.
  30    */
  31   protected readonly aliveInterval?: NodeJS.Timeout
  32   /**
  33    * Constructs a new poolifier worker.
  34    *
  35    * @param type - The type of async event.
  36    * @param isMain - Whether this is the main worker or not.
  37    * @param fn - Function processed by the worker when the pool's `execution` function is invoked.
  38    * @param mainWorker - Reference to main worker.
  39    * @param opts - Options for the worker.
  40    */
  41   public constructor (
  42     type: string,
  43     protected readonly isMain: boolean,
  44     fn: (data: Data) => Response,
  45     protected mainWorker: MainWorker | undefined | null,
  46     protected readonly opts: WorkerOptions = {
  47       /**
  48        * The kill behavior option on this worker or its default value.
  49        */
  50       killBehavior: DEFAULT_KILL_BEHAVIOR,
  51       /**
  52        * The maximum time to keep this worker alive while idle.
  53        * The pool automatically checks and terminates this worker when the time expires.
  54        */
  55       maxInactiveTime: DEFAULT_MAX_INACTIVE_TIME
  56     }
  57   ) {
  58     super(type)
  59     this.checkFunctionInput(fn)
  60     this.checkWorkerOptions(this.opts)
  61     if (!this.isMain) {
  62       this.lastTaskTimestamp = performance.now()
  63       this.aliveInterval = setInterval(
  64         this.checkAlive.bind(this),
  65         (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME) / 2
  66       )
  67       this.checkAlive.bind(this)()
  68     }
  69
  70     this.mainWorker?.on(
  71       'message',
  72       (message: MessageValue<Data, MainWorker>) => {
  73         this.messageListener(message, fn)
  74       }
  75     )
  76   }
  77
  78   /**
  79    * Worker message listener.
  80    *
  81    * @param message - Message received.
  82    * @param fn - Function processed by the worker when the pool's `execution` function is invoked.
  83    */
  84   protected messageListener (
  85     message: MessageValue<Data, MainWorker>,
  86     fn: (data: Data) => Response
  87   ): void {
  88     if (message.data != null && message.id != null) {
  89       // Task message received
  90       if (this.opts.async === true) {
  91         this.runInAsyncScope(this.runAsync.bind(this), this, fn, message)
  92       } else {
  93         this.runInAsyncScope(this.run.bind(this), this, fn, message)
  94       }
  95     } else if (message.parent != null) {
  96       // Main worker reference message received
  97       this.mainWorker = message.parent
  98     } else if (message.kill != null) {
  99       // Kill message received
 100       this.aliveInterval != null && clearInterval(this.aliveInterval)
 101       this.emitDestroy()
 102     }
 103   }
 104
 105   private checkWorkerOptions (opts: WorkerOptions): void {
 106     this.opts.killBehavior = opts.killBehavior ?? DEFAULT_KILL_BEHAVIOR
 107     this.opts.maxInactiveTime =
 108       opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME
 109     this.opts.async = opts.async ?? false
 110   }
 111
 112   /**
 113    * Checks if the `fn` parameter is passed to the constructor.
 114    *
 115    * @param fn - The function that should be defined.
 116    */
 117   private checkFunctionInput (fn: (data: Data) => Response): void {
 118     if (fn == null) throw new Error('fn parameter is mandatory')
 119     if (typeof fn !== 'function') {
 120       throw new TypeError('fn parameter is not a function')
 121     }
 122   }
 123
 124   /**
 125    * Returns the main worker.
 126    *
 127    * @returns Reference to the main worker.
 128    */
 129   protected getMainWorker (): MainWorker {
 130     if (this.mainWorker == null) {
 131       throw new Error('Main worker was not set')
 132     }
 133     return this.mainWorker
 134   }
 135
 136   /**
 137    * Sends a message to the main worker.
 138    *
 139    * @param message - The response message.
 140    */
 141   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 142
 143   /**
 144    * Checks if the worker should be terminated, because its living too long.
 145    */
 146   protected checkAlive (): void {
 147     if (
 148       performance.now() - this.lastTaskTimestamp >
 149       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME)
 150     ) {
 151       this.sendToMainWorker({ kill: this.opts.killBehavior })
 152     }
 153   }
 154
 155   /**
 156    * Handles an error and convert it to a string so it can be sent back to the main worker.
 157    *
 158    * @param e - The error raised by the worker.
 159    * @returns Message of the error.
 160    */
 161   protected handleError (e: Error | string): string {
 162     return e as string
 163   }
 164
 165   /**
 166    * Runs the given function synchronously.
 167    *
 168    * @param fn - Function that will be executed.
 169    * @param message - Input data for the given function.
 170    */
 171   protected run (
 172     fn: (data?: Data) => Response,
 173     message: MessageValue<Data>
 174   ): void {
 175     try {
 176       const startTimestamp = performance.now()
 177       const res = fn(message.data)
 178       const runTime = performance.now() - startTimestamp
 179       this.sendToMainWorker({
 180         data: res,
 181         id: message.id,
 182         runTime
 183       })
 184     } catch (e) {
 185       const err = this.handleError(e as Error)
 186       this.sendToMainWorker({ error: err, id: message.id })
 187     } finally {
 188       !this.isMain && (this.lastTaskTimestamp = performance.now())
 189     }
 190   }
 191
 192   /**
 193    * Runs the given function asynchronously.
 194    *
 195    * @param fn - Function that will be executed.
 196    * @param message - Input data for the given function.
 197    */
 198   protected runAsync (
 199     fn: (data?: Data) => Promise<Response>,
 200     message: MessageValue<Data>
 201   ): void {
 202     const startTimestamp = performance.now()
 203     fn(message.data)
 204       .then(res => {
 205         const runTime = performance.now() - startTimestamp
 206         this.sendToMainWorker({
 207           data: res,
 208           id: message.id,
 209           runTime
 210         })
 211         return null
 212       })
 213       .catch(e => {
 214         const err = this.handleError(e as Error)
 215         this.sendToMainWorker({ error: err, id: message.id })
 216       })
 217       .finally(() => {
 218         !this.isMain && (this.lastTaskTimestamp = performance.now())
 219       })
 220       .catch(EMPTY_FUNCTION)
 221   }
 222 }