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 = 60000
  10 const DEFAULT_KILL_BEHAVIOR: KillBehavior = KillBehaviors.SOFT
  11
  12 /**
  13  * Base class that implements 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    * Options for the worker.
  34    */
  35   public readonly opts: WorkerOptions
  36   /**
  37    * Constructs a new poolifier worker.
  38    *
  39    * @param type The type of async event.
  40    * @param isMain Whether this is the main worker or not.
  41    * @param fn Function processed by the worker when the pool's `execution` function is invoked.
  42    * @param mainWorker Reference to main worker.
  43    * @param opts Options for the worker.
  44    */
  45   public constructor (
  46     type: string,
  47     isMain: boolean,
  48     fn: (data: Data) => Response,
  49     protected mainWorker: MainWorker | undefined | null,
  50     opts: WorkerOptions = {
  51       /**
  52        * The kill behavior option on this Worker or its default value.
  53        */
  54       killBehavior: DEFAULT_KILL_BEHAVIOR,
  55       /**
  56        * The maximum time to keep this worker alive while idle.
  57        * The pool automatically checks and terminates this worker when the time expires.
  58        */
  59       maxInactiveTime: DEFAULT_MAX_INACTIVE_TIME
  60     }
  61   ) {
  62     super(type)
  63     this.opts = opts
  64     this.checkFunctionInput(fn)
  65     this.checkWorkerOptions(this.opts)
  66     this.lastTaskTimestamp = Date.now()
  67     // Keep the worker active
  68     if (!isMain) {
  69       this.aliveInterval = setInterval(
  70         this.checkAlive.bind(this),
  71         (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME) / 2
  72       )
  73       this.checkAlive.bind(this)()
  74     }
  75
  76     this.mainWorker?.on('message', (value: MessageValue<Data, MainWorker>) => {
  77       this.messageListener(value, fn)
  78     })
  79   }
  80
  81   protected messageListener (
  82     value: MessageValue<Data, MainWorker>,
  83     fn: (data: Data) => Response
  84   ): void {
  85     if (value.data !== undefined && value.id !== undefined) {
  86       // Here you will receive messages
  87       if (this.opts.async === true) {
  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 !== undefined) {
  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 !== undefined) {
  97       // Here is time to kill this worker, just clearing the interval
  98       if (this.aliveInterval != null) clearInterval(this.aliveInterval)
  99       this.emitDestroy()
 100     }
 101   }
 102
 103   private checkWorkerOptions (opts: WorkerOptions): void {
 104     this.opts.killBehavior = opts.killBehavior ?? DEFAULT_KILL_BEHAVIOR
 105     this.opts.maxInactiveTime =
 106       opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME
 107     this.opts.async = opts.async ?? false
 108   }
 109
 110   /**
 111    * Checks if the `fn` parameter is passed to the constructor.
 112    *
 113    * @param fn The function that should be defined.
 114    */
 115   private checkFunctionInput (fn: (data: Data) => Response): void {
 116     if (fn == null) throw new Error('fn parameter is mandatory')
 117     if (typeof fn !== 'function') { throw new TypeError('fn parameter is not a function') }
 118   }
 119
 120   /**
 121    * Returns the main worker.
 122    *
 123    * @returns Reference to the main worker.
 124    */
 125   protected getMainWorker (): MainWorker {
 126     if (this.mainWorker == null) {
 127       throw new Error('Main worker was not set')
 128     }
 129     return this.mainWorker
 130   }
 131
 132   /**
 133    * Sends a message to the main worker.
 134    *
 135    * @param message The response message.
 136    */
 137   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 138
 139   /**
 140    * Checks if the worker should be terminated, because its living too long.
 141    */
 142   protected checkAlive (): void {
 143     if (
 144       Date.now() - this.lastTaskTimestamp >
 145       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME)
 146     ) {
 147       this.sendToMainWorker({ kill: this.opts.killBehavior })
 148     }
 149   }
 150
 151   /**
 152    * Handles an error and convert it to a string so it can be sent back to the main worker.
 153    *
 154    * @param e The error raised by the worker.
 155    * @returns Message of the error.
 156    */
 157   protected handleError (e: Error | string): string {
 158     return e as string
 159   }
 160
 161   /**
 162    * Runs the given function synchronously.
 163    *
 164    * @param fn Function that will be executed.
 165    * @param value Input data for the given function.
 166    */
 167   protected run (
 168     fn: (data?: Data) => Response,
 169     value: MessageValue<Data>
 170   ): void {
 171     try {
 172       const startTaskTimestamp = Date.now()
 173       const res = fn(value.data)
 174       const taskRunTime = Date.now() - startTaskTimestamp
 175       this.sendToMainWorker({ data: res, id: value.id, taskRunTime })
 176     } catch (e) {
 177       const err = this.handleError(e as Error)
 178       this.sendToMainWorker({ error: err, id: value.id })
 179     } finally {
 180       this.lastTaskTimestamp = Date.now()
 181     }
 182   }
 183
 184   /**
 185    * Runs the given function asynchronously.
 186    *
 187    * @param fn Function that will be executed.
 188    * @param value Input data for the given function.
 189    */
 190   protected runAsync (
 191     fn: (data?: Data) => Promise<Response>,
 192     value: MessageValue<Data>
 193   ): void {
 194     const startTaskTimestamp = Date.now()
 195     fn(value.data)
 196       .then(res => {
 197         const taskRunTime = Date.now() - startTaskTimestamp
 198         this.sendToMainWorker({ data: res, id: value.id, taskRunTime })
 199         return null
 200       })
 201       .catch(e => {
 202         const err = this.handleError(e as Error)
 203         this.sendToMainWorker({ error: err, id: value.id })
 204       })
 205       .finally(() => {
 206         this.lastTaskTimestamp = Date.now()
 207       })
 208       .catch(EMPTY_FUNCTION)
 209   }
 210 }