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    * 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   /**
  38    * Constructs a new poolifier worker.
  39    *
  40    * @param type The type of async event.
  41    * @param isMain Whether this is the main worker or not.
  42    * @param fn Function processed by the worker when the pool's `execution` function is invoked.
  43    * @param mainWorker Reference to main worker.
  44    * @param opts Options for the worker.
  45    */
  46   public constructor (
  47     type: string,
  48     isMain: boolean,
  49     fn: (data: Data) => Response,
  50     protected mainWorker: MainWorker | undefined | null,
  51     opts: WorkerOptions = {
  52       /**
  53        * The kill behavior option on this Worker or its default value.
  54        */
  55       killBehavior: DEFAULT_KILL_BEHAVIOR,
  56       /**
  57        * The maximum time to keep this worker alive while idle.
  58        * The pool automatically checks and terminates this worker when the time expires.
  59        */
  60       maxInactiveTime: DEFAULT_MAX_INACTIVE_TIME
  61     }
  62   ) {
  63     super(type)
  64     this.opts = opts
  65     this.checkFunctionInput(fn)
  66     this.checkWorkerOptions(this.opts)
  67     this.lastTaskTimestamp = Date.now()
  68     // Keep the worker active
  69     if (!isMain) {
  70       this.aliveInterval = setInterval(
  71         this.checkAlive.bind(this),
  72         (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME) / 2
  73       )
  74       this.checkAlive.bind(this)()
  75     }
  76
  77     this.mainWorker?.on('message', (value: MessageValue<Data, MainWorker>) => {
  78       if (value?.data && value.id) {
  79         // Here you will receive messages
  80         if (this.opts.async) {
  81           this.runInAsyncScope(this.runAsync.bind(this), this, fn, value)
  82         } else {
  83           this.runInAsyncScope(this.run.bind(this), this, fn, value)
  84         }
  85       } else if (value.parent) {
  86         // Save a reference of the main worker to communicate with it
  87         // This will be received once
  88         this.mainWorker = value.parent
  89       } else if (value.kill) {
  90         // Here is time to kill this worker, just clearing the interval
  91         if (this.aliveInterval) clearInterval(this.aliveInterval)
  92         this.emitDestroy()
  93       }
  94     })
  95   }
  96
  97   private checkWorkerOptions (opts: WorkerOptions) {
  98     this.opts.killBehavior = opts.killBehavior ?? DEFAULT_KILL_BEHAVIOR
  99     this.opts.maxInactiveTime =
 100       opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME
 101     /**
 102      * Whether the worker is working asynchronously or not.
 103      */
 104     this.opts.async = !!opts.async
 105   }
 106
 107   /**
 108    * Check if the `fn` parameter is passed to the constructor.
 109    *
 110    * @param fn The function that should be defined.
 111    */
 112   private checkFunctionInput (fn: (data: Data) => Response): void {
 113     if (!fn) throw new Error('fn parameter is mandatory')
 114   }
 115
 116   /**
 117    * Returns the main worker.
 118    *
 119    * @returns Reference to the main worker.
 120    */
 121   protected getMainWorker (): MainWorker {
 122     if (!this.mainWorker) {
 123       throw new Error('Main worker was not set')
 124     }
 125     return this.mainWorker
 126   }
 127
 128   /**
 129    * Send a message to the main worker.
 130    *
 131    * @param message The response message.
 132    */
 133   protected abstract sendToMainWorker (message: MessageValue<Response>): void
 134
 135   /**
 136    * Check to see if the worker should be terminated, because its living too long.
 137    */
 138   protected checkAlive (): void {
 139     if (
 140       Date.now() - this.lastTaskTimestamp >
 141       (this.opts.maxInactiveTime ?? DEFAULT_MAX_INACTIVE_TIME)
 142     ) {
 143       this.sendToMainWorker({ kill: this.opts.killBehavior })
 144     }
 145   }
 146
 147   /**
 148    * Handle an error and convert it to a string so it can be sent back to the main worker.
 149    *
 150    * @param e The error raised by the worker.
 151    * @returns Message of the error.
 152    */
 153   protected handleError (e: Error | string): string {
 154     return e as string
 155   }
 156
 157   /**
 158    * Run the given function synchronously.
 159    *
 160    * @param fn Function that will be executed.
 161    * @param value Input data for the given function.
 162    */
 163   protected run (
 164     fn: (data?: Data) => Response,
 165     value: MessageValue<Data>
 166   ): void {
 167     try {
 168       const res = fn(value.data)
 169       this.sendToMainWorker({ data: res, id: value.id })
 170     } catch (e) {
 171       const err = this.handleError(e as Error)
 172       this.sendToMainWorker({ error: err, id: value.id })
 173     } finally {
 174       this.lastTaskTimestamp = Date.now()
 175     }
 176   }
 177
 178   /**
 179    * Run the given function asynchronously.
 180    *
 181    * @param fn Function that will be executed.
 182    * @param value Input data for the given function.
 183    */
 184   protected runAsync (
 185     fn: (data?: Data) => Promise<Response>,
 186     value: MessageValue<Data>
 187   ): void {
 188     fn(value.data)
 189       .then(res => {
 190         this.sendToMainWorker({ data: res, id: value.id })
 191         return null
 192       })
 193       .catch(e => {
 194         const err = this.handleError(e as Error)
 195         this.sendToMainWorker({ error: err, id: value.id })
 196       })
 197       .finally(() => {
 198         this.lastTaskTimestamp = Date.now()
 199       })
 200       .catch(EMPTY_FUNCTION)
 201   }
 202 }