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 { WorkerOptions } from './worker-options'
   6 import { killBehaviorEnumeration } from './worker-options'
   7
   8 const defaultMaxInactiveTime = 1000 * 60
   9 const defaultKillBehavior = killBehaviorEnumeration.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: string
  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    * Constructs a new poolifier worker.
  46    *
  47    * @param type The type of async event.
  48    * @param isMain Whether this is the main worker or not.
  49    * @param fn Function processed by the worker when the pool's `execution` function is invoked.
  50    * @param mainWorker Reference to main worker.
  51    * @param opts Options for the worker.
  52    */
  53   public constructor (
  54     type: string,
  55     isMain: boolean,
  56     fn: (data: Data) => Response,
  57     protected mainWorker?: MainWorker | null,
  58     public readonly opts: WorkerOptions = {
  59       killBehavior: defaultKillBehavior,
  60       maxInactiveTime: defaultMaxInactiveTime
  61     }
  62   ) {
  63     super(type)
  64     this.killBehavior = this.opts.killBehavior ?? defaultKillBehavior
  65     this.maxInactiveTime = this.opts.maxInactiveTime ?? defaultMaxInactiveTime
  66     this.async = !!this.opts.async
  67     this.lastTask = Date.now()
  68     if (!fn) throw new Error('fn parameter is mandatory')
  69     // Keep the worker active
  70     if (!isMain) {
  71       this.interval = setInterval(
  72         this.checkAlive.bind(this),
  73         this.maxInactiveTime / 2
  74       )
  75       this.checkAlive.bind(this)()
  76     }
  77
  78     this.mainWorker?.on('message', (value: MessageValue<Data, MainWorker>) => {
  79       if (value?.data && value.id) {
  80         // Here you will receive messages
  81         if (this.async) {
  82           this.runInAsyncScope(this.runAsync.bind(this), this, fn, value)
  83         } else {
  84           this.runInAsyncScope(this.run.bind(this), this, fn, value)
  85         }
  86       } else if (value.parent) {
  87         // Save a reference of the main worker to communicate with it
  88         // This will be received once
  89         this.mainWorker = value.parent
  90       } else if (value.kill) {
  91         // Here is time to kill this worker, just clearing the interval
  92         if (this.interval) clearInterval(this.interval)
  93         this.emitDestroy()
  94       }
  95     })
  96   }
  97
  98   /**
  99    * Returns the main worker.
 100    *
 101    * @returns Reference to the main worker.
 102    */
 103   protected getMainWorker (): MainWorker {
 104     if (!this.mainWorker) {
 105       throw new Error('Main worker was not set')
 106     }
 107     return this.mainWorker
 108   }
 109
 110   /**
 111    * Send a message to the main worker.
 112    *
 113    * @param message The response message.
 114    */
 115   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 116
 117   /**
 118    * Check to see if the worker should be terminated, because its living too long.
 119    */
 120   protected checkAlive (): void {
 121     if (Date.now() - this.lastTask > this.maxInactiveTime) {
 122       this.sendToMainWorker({ kill: this.killBehavior })
 123     }
 124   }
 125
 126   /**
 127    * Handle an error and convert it to a string so it can be sent back to the main worker.
 128    *
 129    * @param e The error raised by the worker.
 130    * @returns Message of the error.
 131    */
 132   protected handleError (e: Error | string): string {
 133     return (e as unknown) as string
 134   }
 135
 136   /**
 137    * Run the given function synchronously.
 138    *
 139    * @param fn Function that will be executed.
 140    * @param value Input data for the given function.
 141    */
 142   protected run (
 143     fn: (data?: Data) => Response,
 144     value: MessageValue<Data>
 145   ): void {
 146     try {
 147       const res = fn(value.data)
 148       this.sendToMainWorker({ data: res, id: value.id })
 149       this.lastTask = Date.now()
 150     } catch (e) {
 151       const err = this.handleError(e)
 152       this.sendToMainWorker({ error: err, id: value.id })
 153       this.lastTask = Date.now()
 154     }
 155   }
 156
 157   /**
 158    * Run the given function asynchronously.
 159    *
 160    * @param fn Function that will be executed.
 161    * @param value Input data for the given function.
 162    */
 163   protected runAsync (
 164     fn: (data?: Data) => Promise<Response>,
 165     value: MessageValue<Data>
 166   ): void {
 167     fn(value.data)
 168       .then(res => {
 169         this.sendToMainWorker({ data: res, id: value.id })
 170         this.lastTask = Date.now()
 171         return null
 172       })
 173       .catch(e => {
 174         const err = this.handleError(e)
 175         this.sendToMainWorker({ error: err, id: value.id })
 176         this.lastTask = Date.now()
 177       })
 178   }
 179 }