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 type { KillBehavior, WorkerOptions } from './worker-options'
   6 import { KillBehaviors } from './worker-options'
   7
   8 const DEFAULT_MAX_INACTIVE_TIME = 1000 * 60
   9 const DEFAULT_KILL_BEHAVIOR: KillBehavior = KillBehaviors.SOFT
  10
  11 /**
  12  * Base class containing some shared logic for all poolifier workers.
  13  *
  14  * @template MainWorker Type of main worker.
  15  * @template Data Type of data this worker receives from pool's execution.
  16  * @template Response Type of response the worker sends back to the main worker.
  17  */
  18 export abstract class AbstractWorker<
  19   MainWorker extends Worker | MessagePort,
  20   Data = unknown,
  21   Response = unknown
  22 > extends AsyncResource {
  23   /**
  24    * The maximum time to keep this worker alive while idle. The pool automatically checks and terminates this worker when the time expires.
  25    */
  26   protected readonly maxInactiveTime: number
  27   /**
  28    * The kill behavior set as option on the Worker constructor or a default value.
  29    */
  30   protected readonly killBehavior: KillBehavior
  31   /**
  32    * Whether the worker is working asynchronously or not.
  33    */
  34   protected readonly async: boolean
  35   /**
  36    * Timestamp of the last task processed by this worker.
  37    */
  38   protected lastTask: number
  39   /**
  40    * Handler ID of the `interval` alive check.
  41    */
  42   protected readonly interval?: NodeJS.Timeout
  43
  44   /**
  45    * This value is immediately set to true when the kill from the main worker is received.
  46    */
  47   private isKilled: boolean = false
  48
  49   /**
  50    * Constructs a new poolifier worker.
  51    *
  52    * @param type The type of async event.
  53    * @param isMain Whether this is the main worker or not.
  54    * @param fn Function processed by the worker when the pool's `execution` function is invoked.
  55    * @param mainWorker Reference to main worker.
  56    * @param opts Options for the worker.
  57    */
  58   public constructor (
  59     type: string,
  60     isMain: boolean,
  61     fn: (data: Data) => Response,
  62     protected mainWorker?: MainWorker | null,
  63     public readonly opts: WorkerOptions = {
  64       killBehavior: DEFAULT_KILL_BEHAVIOR,
  65       maxInactiveTime: DEFAULT_MAX_INACTIVE_TIME
  66     }
  67   ) {
  68     super(type)
  69     this.killBehavior = this.opts.killBehavior ?? DEFAULT_KILL_BEHAVIOR
  70     this.maxInactiveTime =
  71       this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME
  72     this.async = !!this.opts.async
  73     this.lastTask = Date.now()
  74     this.checkFunctionInput(fn)
  75     // Keep the worker active
  76     if (!isMain) {
  77       this.interval = setInterval(
  78         this.checkAlive.bind(this),
  79         this.maxInactiveTime / 2
  80       )
  81       this.checkAlive.bind(this)()
  82     }
  83
  84     this.mainWorker?.on('message', (value: MessageValue<Data, MainWorker>) => {
  85       if (value?.data && value.id) {
  86         // Here you will receive messages
  87         if (this.async) {
  88           this.runInAsyncScope(this.runAsync.bind(this), this, fn, value)
  89         } else {
  90           this.runInAsyncScope(this.run.bind(this), this, fn, value)
  91         }
  92       } else if (value.parent) {
  93         // Save a reference of the main worker to communicate with it
  94         // This will be received once
  95         this.mainWorker = value.parent
  96       } else if (value.kill) {
  97         // Here is time to kill this worker, just clearing the interval
  98         this.isKilled = true
  99         if (this.interval) clearInterval(this.interval)
 100         this.emitDestroy()
 101       }
 102     })
 103   }
 104
 105   /**
 106    * Check if the `fn` parameter is passed to the constructor.
 107    *
 108    * @param fn The function that should be defined.
 109    */
 110   private checkFunctionInput (fn: (data: Data) => Response) {
 111     if (!fn) throw new Error('fn parameter is mandatory')
 112   }
 113
 114   /**
 115    * Returns the main worker.
 116    *
 117    * @returns Reference to the main worker.
 118    */
 119   protected getMainWorker (): MainWorker {
 120     if (!this.mainWorker) {
 121       throw new Error('Main worker was not set')
 122     }
 123     return this.mainWorker
 124   }
 125
 126   /**
 127    * Send a message to the main worker.
 128    *
 129    * @param message The response message.
 130    */
 131   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 132
 133   /**
 134    * Check to see if the worker should be terminated, because its living too long.
 135    */
 136   protected checkAlive (): void {
 137     if (Date.now() - this.lastTask > this.maxInactiveTime && !this.isKilled) {
 138       this.sendToMainWorker({ kill: this.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 unknown) 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       this.lastTask = Date.now()
 166     } catch (e) {
 167       const err = this.handleError(e)
 168       this.sendToMainWorker({ error: err, id: value.id })
 169       this.lastTask = 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         this.lastTask = Date.now()
 187         return null
 188       })
 189       .catch(e => {
 190         const err = this.handleError(e)
 191         this.sendToMainWorker({ error: err, id: value.id })
 192         this.lastTask = Date.now()
 193       })
 194   }
 195 }