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    * 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: DEFAULT_KILL_BEHAVIOR,
  60       maxInactiveTime: DEFAULT_MAX_INACTIVE_TIME
  61     }
  62   ) {
  63     super(type)
  64     this.killBehavior = this.opts.killBehavior ?? DEFAULT_KILL_BEHAVIOR
  65     this.maxInactiveTime =
  66       this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME
  67     this.async = !!this.opts.async
  68     this.lastTask = Date.now()
  69     if (!fn) throw new Error('fn parameter is mandatory')
  70     // Keep the worker active
  71     if (!isMain) {
  72       this.interval = setInterval(
  73         this.checkAlive.bind(this),
  74         this.maxInactiveTime / 2
  75       )
  76       this.checkAlive.bind(this)()
  77     }
  78
  79     this.mainWorker?.on('message', (value: MessageValue<Data, MainWorker>) => {
  80       if (value?.data && value.id) {
  81         // Here you will receive messages
  82         if (this.async) {
  83           this.runInAsyncScope(this.runAsync.bind(this), this, fn, value)
  84         } else {
  85           this.runInAsyncScope(this.run.bind(this), this, fn, value)
  86         }
  87       } else if (value.parent) {
  88         // Save a reference of the main worker to communicate with it
  89         // This will be received once
  90         this.mainWorker = value.parent
  91       } else if (value.kill) {
  92         // Here is time to kill this worker, just clearing the interval
  93         if (this.interval) clearInterval(this.interval)
  94         this.emitDestroy()
  95       }
  96     })
  97   }
  98
  99   /**
 100    * Returns the main worker.
 101    *
 102    * @returns Reference to the main worker.
 103    */
 104   protected getMainWorker (): MainWorker {
 105     if (!this.mainWorker) {
 106       throw new Error('Main worker was not set')
 107     }
 108     return this.mainWorker
 109   }
 110
 111   /**
 112    * Send a message to the main worker.
 113    *
 114    * @param message The response message.
 115    */
 116   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 117
 118   /**
 119    * Check to see if the worker should be terminated, because its living too long.
 120    */
 121   protected checkAlive (): void {
 122     if (Date.now() - this.lastTask > this.maxInactiveTime) {
 123       this.sendToMainWorker({ kill: this.killBehavior })
 124     }
 125   }
 126
 127   /**
 128    * Handle an error and convert it to a string so it can be sent back to the main worker.
 129    *
 130    * @param e The error raised by the worker.
 131    * @returns Message of the error.
 132    */
 133   protected handleError (e: Error | string): string {
 134     return (e as unknown) as string
 135   }
 136
 137   /**
 138    * Run the given function synchronously.
 139    *
 140    * @param fn Function that will be executed.
 141    * @param value Input data for the given function.
 142    */
 143   protected run (
 144     fn: (data?: Data) => Response,
 145     value: MessageValue<Data>
 146   ): void {
 147     try {
 148       const res = fn(value.data)
 149       this.sendToMainWorker({ data: res, id: value.id })
 150       this.lastTask = Date.now()
 151     } catch (e) {
 152       const err = this.handleError(e)
 153       this.sendToMainWorker({ error: err, id: value.id })
 154       this.lastTask = Date.now()
 155     }
 156   }
 157
 158   /**
 159    * Run the given function asynchronously.
 160    *
 161    * @param fn Function that will be executed.
 162    * @param value Input data for the given function.
 163    */
 164   protected runAsync (
 165     fn: (data?: Data) => Promise<Response>,
 166     value: MessageValue<Data>
 167   ): void {
 168     fn(value.data)
 169       .then(res => {
 170         this.sendToMainWorker({ data: res, id: value.id })
 171         this.lastTask = Date.now()
 172         return null
 173       })
 174       .catch(e => {
 175         const err = this.handleError(e)
 176         this.sendToMainWorker({ error: err, id: value.id })
 177         this.lastTask = Date.now()
 178       })
 179   }
 180 }