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    * The maximum time to keep this worker alive while idle. The pool automatically checks and terminates this worker when the time expires.
  26    */
  27   protected readonly maxInactiveTime: number
  28   /**
  29    * The kill behavior set as option on the Worker constructor or a default value.
  30    */
  31   protected readonly killBehavior: KillBehavior
  32   /**
  33    * Whether the worker is working asynchronously or not.
  34    */
  35   protected readonly async: boolean
  36   /**
  37    * Timestamp of the last task processed by this worker.
  38    */
  39   protected lastTask: number
  40   /**
  41    * Handler ID of the `interval` alive check.
  42    */
  43   protected readonly interval?: NodeJS.Timeout
  44
  45   /**
  46    * Constructs a new poolifier worker.
  47    *
  48    * @param type The type of async event.
  49    * @param isMain Whether this is the main worker or not.
  50    * @param fn Function processed by the worker when the pool's `execution` function is invoked.
  51    * @param mainWorker Reference to main worker.
  52    * @param opts Options for the worker.
  53    */
  54   public constructor (
  55     type: string,
  56     isMain: boolean,
  57     fn: (data: Data) => Response,
  58     protected mainWorker?: MainWorker | null,
  59     public readonly opts: WorkerOptions = {
  60       killBehavior: DEFAULT_KILL_BEHAVIOR,
  61       maxInactiveTime: DEFAULT_MAX_INACTIVE_TIME
  62     }
  63   ) {
  64     super(type)
  65     this.killBehavior = this.opts.killBehavior ?? DEFAULT_KILL_BEHAVIOR
  66     this.maxInactiveTime =
  67       this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME
  68     this.async = !!this.opts.async
  69     this.lastTask = Date.now()
  70     this.checkFunctionInput(fn)
  71     // Keep the worker active
  72     if (!isMain) {
  73       this.interval = setInterval(
  74         this.checkAlive.bind(this),
  75         this.maxInactiveTime / 2
  76       )
  77       this.checkAlive.bind(this)()
  78     }
  79
  80     this.mainWorker?.on('message', (value: MessageValue<Data, MainWorker>) => {
  81       if (value?.data && value.id) {
  82         // Here you will receive messages
  83         if (this.async) {
  84           this.runInAsyncScope(this.runAsync.bind(this), this, fn, value)
  85         } else {
  86           this.runInAsyncScope(this.run.bind(this), this, fn, value)
  87         }
  88       } else if (value.parent) {
  89         // Save a reference of the main worker to communicate with it
  90         // This will be received once
  91         this.mainWorker = value.parent
  92       } else if (value.kill) {
  93         // Here is time to kill this worker, just clearing the interval
  94         if (this.interval) clearInterval(this.interval)
  95         this.emitDestroy()
  96       }
  97     })
  98   }
  99
 100   /**
 101    * Check if the `fn` parameter is passed to the constructor.
 102    *
 103    * @param fn The function that should be defined.
 104    */
 105   private checkFunctionInput (fn: (data: Data) => Response): void {
 106     if (!fn) throw new Error('fn parameter is mandatory')
 107   }
 108
 109   /**
 110    * Returns the main worker.
 111    *
 112    * @returns Reference to the main worker.
 113    */
 114   protected getMainWorker (): MainWorker {
 115     if (!this.mainWorker) {
 116       throw new Error('Main worker was not set')
 117     }
 118     return this.mainWorker
 119   }
 120
 121   /**
 122    * Send a message to the main worker.
 123    *
 124    * @param message The response message.
 125    */
 126   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 127
 128   /**
 129    * Check to see if the worker should be terminated, because its living too long.
 130    */
 131   protected checkAlive (): void {
 132     if (Date.now() - this.lastTask > this.maxInactiveTime) {
 133       this.sendToMainWorker({ kill: this.killBehavior })
 134     }
 135   }
 136
 137   /**
 138    * Handle an error and convert it to a string so it can be sent back to the main worker.
 139    *
 140    * @param e The error raised by the worker.
 141    * @returns Message of the error.
 142    */
 143   protected handleError (e: Error | string): string {
 144     return (e as unknown) as string
 145   }
 146
 147   /**
 148    * Run the given function synchronously.
 149    *
 150    * @param fn Function that will be executed.
 151    * @param value Input data for the given function.
 152    */
 153   protected run (
 154     fn: (data?: Data) => Response,
 155     value: MessageValue<Data>
 156   ): void {
 157     try {
 158       const res = fn(value.data)
 159       this.sendToMainWorker({ data: res, id: value.id })
 160     } catch (e) {
 161       const err = this.handleError(e)
 162       this.sendToMainWorker({ error: err, id: value.id })
 163     } finally {
 164       this.lastTask = Date.now()
 165     }
 166   }
 167
 168   /**
 169    * Run the given function asynchronously.
 170    *
 171    * @param fn Function that will be executed.
 172    * @param value Input data for the given function.
 173    */
 174   protected runAsync (
 175     fn: (data?: Data) => Promise<Response>,
 176     value: MessageValue<Data>
 177   ): void {
 178     fn(value.data)
 179       .then(res => {
 180         this.sendToMainWorker({ data: res, id: value.id })
 181         return null
 182       })
 183       .catch(e => {
 184         const err = this.handleError(e)
 185         this.sendToMainWorker({ error: err, id: value.id })
 186       })
 187       .finally(() => {
 188         this.lastTask = Date.now()
 189       })
 190       .catch(EMPTY_FUNCTION)
 191   }
 192 }