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 === false) {
  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) clearInterval(this.aliveInterval)
  99       this.emitDestroy()
 100     }
 101   }
 102
 103   private checkWorkerOptions (opts: WorkerOptions) {
 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
 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) throw new Error('fn parameter is mandatory')
 117   }
 118
 119   /**
 120    * Returns the main worker.
 121    *
 122    * @returns Reference to the main worker.
 123    */
 124   protected getMainWorker (): MainWorker {
 125     if (!this.mainWorker) {
 126       throw new Error('Main worker was not set')
 127     }
 128     return this.mainWorker
 129   }
 130
 131   /**
 132    * Sends a message to the main worker.
 133    *
 134    * @param message The response message.
 135    */
 136   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 137
 138   /**
 139    * Checks if the worker should be terminated, because its living too long.
 140    */
 141   protected checkAlive (): void {
 142     if (
 143       Date.now() - this.lastTaskTimestamp >
 144       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME)
 145     ) {
 146       this.sendToMainWorker({ kill: this.opts.killBehavior })
 147     }
 148   }
 149
 150   /**
 151    * Handles an error and convert it to a string so it can be sent back to the main worker.
 152    *
 153    * @param e The error raised by the worker.
 154    * @returns Message of the error.
 155    */
 156   protected handleError (e: Error | string): string {
 157     return e as string
 158   }
 159
 160   /**
 161    * Runs the given function synchronously.
 162    *
 163    * @param fn Function that will be executed.
 164    * @param value Input data for the given function.
 165    */
 166   protected run (
 167     fn: (data?: Data) => Response,
 168     value: MessageValue<Data>
 169   ): void {
 170     try {
 171       const startTaskTimestamp = Date.now()
 172       const res = fn(value.data)
 173       const taskRunTime = Date.now() - startTaskTimestamp
 174       this.sendToMainWorker({ data: res, id: value.id, taskRunTime })
 175     } catch (e) {
 176       const err = this.handleError(e as Error)
 177       this.sendToMainWorker({ error: err, id: value.id })
 178     } finally {
 179       this.lastTaskTimestamp = Date.now()
 180     }
 181   }
 182
 183   /**
 184    * Runs the given function asynchronously.
 185    *
 186    * @param fn Function that will be executed.
 187    * @param value Input data for the given function.
 188    */
 189   protected runAsync (
 190     fn: (data?: Data) => Promise<Response>,
 191     value: MessageValue<Data>
 192   ): void {
 193     const startTaskTimestamp = Date.now()
 194     fn(value.data)
 195       .then(res => {
 196         const taskRunTime = Date.now() - startTaskTimestamp
 197         this.sendToMainWorker({ data: res, id: value.id, taskRunTime })
 198         return null
 199       })
 200       .catch(e => {
 201         const err = this.handleError(e as Error)
 202         this.sendToMainWorker({ error: err, id: value.id })
 203       })
 204       .finally(() => {
 205         this.lastTaskTimestamp = Date.now()
 206       })
 207       .catch(EMPTY_FUNCTION)
 208   }
 209 }