src/worker/abstract-worker.ts

   1 import { AsyncResource } from 'async_hooks'
   2 import type { Worker } from 'cluster'
   3 import type { MessagePort } from '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 = 1000 * 60
  10 const DEFAULT_KILL_BEHAVIOR: KillBehavior = KillBehaviors.SOFT
  11
  12 /**
  13  * Base class containing some shared logic for all poolifier workers.
  14  *
  15  * @template MainWorker Type of main worker.
  16  * @template Data Type of data this worker receives from pool's execution. This can only be serializable data.
  17  * @template 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   /**
  34    * Constructs a new poolifier worker.
  35    *
  36    * @param type The type of async event.
  37    * @param isMain Whether this is the main worker or not.
  38    * @param fn Function processed by the worker when the pool's `execution` function is invoked.
  39    * @param mainWorker Reference to main worker.
  40    * @param opts Options for the worker.
  41    */
  42   public constructor (
  43     type: string,
  44     isMain: boolean,
  45     fn: (data: Data) => Response,
  46     protected mainWorker: MainWorker | undefined | null,
  47     public readonly opts: WorkerOptions = {
  48       /**
  49        * The kill behavior option on this Worker or its default value.
  50        */
  51       killBehavior: DEFAULT_KILL_BEHAVIOR,
  52       /**
  53        * The maximum time to keep this worker alive while idle.
  54        * The pool automatically checks and terminates this worker when the time expires.
  55        */
  56       maxInactiveTime: DEFAULT_MAX_INACTIVE_TIME
  57     }
  58   ) {
  59     super(type)
  60     this.checkFunctionInput(fn)
  61     this.checkWorkerOptions(this.opts)
  62     this.lastTaskTimestamp = Date.now()
  63     // Keep the worker active
  64     if (!isMain) {
  65       this.aliveInterval = setInterval(
  66         this.checkAlive.bind(this),
  67         (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME) / 2
  68       )
  69       this.checkAlive.bind(this)()
  70     }
  71
  72     this.mainWorker?.on('message', (value: MessageValue<Data, MainWorker>) => {
  73       if (value?.data && value.id) {
  74         // Here you will receive messages
  75         if (this.opts.async) {
  76           this.runInAsyncScope(this.runAsync.bind(this), this, fn, value)
  77         } else {
  78           this.runInAsyncScope(this.run.bind(this), this, fn, value)
  79         }
  80       } else if (value.parent) {
  81         // Save a reference of the main worker to communicate with it
  82         // This will be received once
  83         this.mainWorker = value.parent
  84       } else if (value.kill) {
  85         // Here is time to kill this worker, just clearing the interval
  86         if (this.aliveInterval) clearInterval(this.aliveInterval)
  87         this.emitDestroy()
  88       }
  89     })
  90   }
  91
  92   private checkWorkerOptions (opts: WorkerOptions) {
  93     this.opts.killBehavior = opts.killBehavior ?? DEFAULT_KILL_BEHAVIOR
  94     this.opts.maxInactiveTime =
  95       opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME
  96     /**
  97      * Whether the worker is working asynchronously or not.
  98      */
  99     this.opts.async = !!opts.async
 100   }
 101
 102   /**
 103    * Check if the `fn` parameter is passed to the constructor.
 104    *
 105    * @param fn The function that should be defined.
 106    */
 107   private checkFunctionInput (fn: (data: Data) => Response): void {
 108     if (!fn) throw new Error('fn parameter is mandatory')
 109   }
 110
 111   /**
 112    * Returns the main worker.
 113    *
 114    * @returns Reference to the main worker.
 115    */
 116   protected getMainWorker (): MainWorker {
 117     if (!this.mainWorker) {
 118       throw new Error('Main worker was not set')
 119     }
 120     return this.mainWorker
 121   }
 122
 123   /**
 124    * Send a message to the main worker.
 125    *
 126    * @param message The response message.
 127    */
 128   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 129
 130   /**
 131    * Check to see if the worker should be terminated, because its living too long.
 132    */
 133   protected checkAlive (): void {
 134     if (
 135       Date.now() - this.lastTaskTimestamp >
 136       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME)
 137     ) {
 138       this.sendToMainWorker({ kill: this.opts.killBehavior })
 139     }
 140   }
 141
 142   /**
 143    * Handle an error and convert it to a string so it can be sent back to the main worker.
 144    *
 145    * @param e The error raised by the worker.
 146    * @returns Message of the error.
 147    */
 148   protected handleError (e: Error | string): string {
 149     return e as string
 150   }
 151
 152   /**
 153    * Run the given function synchronously.
 154    *
 155    * @param fn Function that will be executed.
 156    * @param value Input data for the given function.
 157    */
 158   protected run (
 159     fn: (data?: Data) => Response,
 160     value: MessageValue<Data>
 161   ): void {
 162     try {
 163       const res = fn(value.data)
 164       this.sendToMainWorker({ data: res, id: value.id })
 165     } catch (e) {
 166       const err = this.handleError(e as Error)
 167       this.sendToMainWorker({ error: err, id: value.id })
 168     } finally {
 169       this.lastTaskTimestamp = Date.now()
 170     }
 171   }
 172
 173   /**
 174    * Run the given function asynchronously.
 175    *
 176    * @param fn Function that will be executed.
 177    * @param value Input data for the given function.
 178    */
 179   protected runAsync (
 180     fn: (data?: Data) => Promise<Response>,
 181     value: MessageValue<Data>
 182   ): void {
 183     fn(value.data)
 184       .then(res => {
 185         this.sendToMainWorker({ data: res, id: value.id })
 186         return null
 187       })
 188       .catch(e => {
 189         const err = this.handleError(e)
 190         this.sendToMainWorker({ error: err, id: value.id })
 191       })
 192       .finally(() => {
 193         this.lastTaskTimestamp = Date.now()
 194       })
 195       .catch(EMPTY_FUNCTION)
 196   }
 197 }