Best Online Tutorials

SQL Tutorial

Free SQL Tutorial

SQL Interview Questions

SQL Practice Questions

SQL Tips & Tricks

SQL Errors

SQL Books

Angular Tutorial

Free Angular Tutorial

Angular Interview Questions

Angular Practice Questions

Angular Tips & Tricks

Angular Errors

Angular Books

Node.js Tutorial

Free Node.js Tutorial

Node.js Interview Questions

Node.js Practice Questions

Node.js Tips & Tricks

Node.js Errors

Node.js Books

React.js Tutorial

Free React.js Tutorial

React.js Interview Questions

React.js Practice Questions

React.js Tips & Tricks

React.js Errors

React.js Books

SSIS Tutorial

Free SSIS Tutorial

SSIS Interview Questions

SSIS Practice Questions

SSIS Tips & Tricks

SSIS Errors

SSIS Books

SEO Tutorial

Free SEO Tutorial

SEO Interview Questions

SEO Practice Questions

SEO Tips & Tricks

SEO Errors

SEO Books

Javascript Tutorial

Free Javascript Tutorial

Javascript Interview Questions

Javascript Practice Questions

Javascript Tips & Tricks

Javascript Errors

Javascript Books

MongoDB Tutorial

Free MongoDB Tutorial

MongoDB Interview Questions

MongoDB Practice Questions

MongoDB Tips & Tricks

MongoDB Errors

MongoDB Books

Next.js Tutorial

Free Next.js Tutorial

Next.js Interview Questions

Next.js Practice Questions

Next.js Tips & Tricks

Next.js Errors

Next.js Books

Node.js - Async Hooks 

Prashant Surya  |   Nov 19, 2019  |  Views: 16

Description:

Async hooks (async_hooks) in node.js is a module which provides the API to register the callbacks.

These hooks keeps the track of the lifetime of asynchronous resources inside the given callback.

It helps us in Error tracking.


Example of the async resources:
  • fs.open();
  • net.createServer();

Note:
  • If we are using workers in our application, each worker will have independent async_hooks interface.
  • Each thread will get a new set of async IDs.

How to import in application:
const async_hooks = require('async_hooks');

How to add a callback in async_hook:
async_hooks.createHook(callbacks)
Callback types:

  • init <Function> :  The init callback.
  • before <Function> : The before callback.
  • after <Function> : The after callback.
  • destroy <Function> : The destroy callback.
These all callbacks are optional while creating a hook


const asyncHook =
    async_hooks.createHook({ init, before, after, destroy, promiseResolve });

const async_hooks = require('async_hooks');

// It Returns the ID of the current execution context.
const eid = async_hooks.executionAsyncId();

// It Returns the ID of the handle responsible for triggering the callback of the
// current execution scope to call.
const tid = async_hooks.triggerAsyncId();

// It Creates a new AsyncHook instance. All of these callbacks are optional.
const asyncHook =
    async_hooks.createHook({ init, before, after, destroy, promiseResolve });

// Allow callbacks of this AsyncHook instance to call. This is not an implicit
// action after running the constructor, and must be explicitly run to begin
// executing callbacks.
asyncHook.enable();

// Disable listening for new asynchronous events.
asyncHook.disable();

//
// The following are the callbacks that can be passed to createHook().
//

// init is called during object construction. The resource may not have
// completed construction when this callback runs, therefore all fields of the
// resource referenced by "asyncId" may not have been populated.
function init(asyncId, type, triggerAsyncId, resource) { }

// Before is called just before the resource's callback is called. It can be
// called 0-N times for handles (e.g. TCPWrap), and will be called exactly 1
// time for requests (e.g. FSReqCallback).
function before(asyncId) { }

// After is called just after the resource's callback has finished.
function after(asyncId) { }

// Destroy is called when an AsyncWrap instance is destroyed.
function destroy(asyncId) { }

// promiseResolve is called only for promise resources, when the
// `resolve` function passed to the `Promise` constructor is invoked
// (either directly or through other means of resolving a promise).
function promiseResolve(asyncId) { }







Comments:
Content Contributor
Prashant Surya

Prashant Surya

Software developer at Uniserve Data Technologies Pvt. Ltd.  |   Noida, Uttar Pradesh, India

I am a software developer, freelancer and trainer working on technologies likes. MEAN stack, MERN Stack, ASP.NET full stack, WebRTC, socket.io ,PWA, SQL, JavaScript, jQuery, HTML, CSS, SEO, responsive UI/UX designing... having 7 years of experience in development in multiple domains like, eCommerce, RTA, capital markets, education, real estate...


Read related articles

Node.js - Modules

Prashant Surya  |   Dec 26, 2019  |  Views: 11

Node.js - Cluster

Prashant Surya  |   Nov 19, 2019  |  Views: 12

Node.js - IPC

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Node.js - OS

Prashant Surya  |   Nov 19, 2019  |  Views: 7

Node.js - Global Objects

Prashant Surya  |   Nov 19, 2019  |  Views: 13

Node.js - Command Line Options

Prashant Surya  |   Nov 19, 2019  |  Views: 19

Node.js - Callbacks

Prashant Surya  |   Nov 19, 2019  |  Views: 11

Node.js - NPM

Prashant Surya  |   Nov 19, 2019  |  Views: 8

Node.js - REPL

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Node.js - Console

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Node.js - First Example

Prashant Surya  |   Nov 19, 2019  |  Views: 13

Node.js - Installation

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Node.js - Introduction

Prashant Surya  |   Nov 19, 2019  |  Views: 17

Node.js - Http

Prashant Surya  |   Nov 19, 2019  |  Views: 11

Node.js - Timer

Prashant Surya  |   Nov 19, 2019  |  Views: 17

Node.js - Crypto

Prashant Surya  |   Nov 19, 2019  |  Views: 10

Node.js - Errors

Prashant Surya  |   Nov 19, 2019  |  Views: 13

Node.js - File System

Prashant Surya  |   Nov 19, 2019  |  Views: 10

Node.js - Http/2

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Node.js - Query String

Prashant Surya  |   Nov 19, 2019  |  Views: 8

Node.js - Async Hooks

Prashant Surya  |   Nov 19, 2019  |  Views: 17

Node.js - Https

Prashant Surya  |   Nov 19, 2019  |  Views: 8

Node.js - String Decoder

Prashant Surya  |   Nov 19, 2019  |  Views: 12

Node.js - DNS

Prashant Surya  |   Nov 19, 2019  |  Views: 8

Node.js - Debugger

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Node.js - TLS/SSL

Prashant Surya  |   Nov 19, 2019  |  Views: 13

Node.js - Child Process

Prashant Surya  |   Nov 19, 2019  |  Views: 13

Node.js - Process

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Node.js - Streams

Prashant Surya  |   Nov 19, 2019  |  Views: 13

Node.js - Net

Prashant Surya  |   Nov 19, 2019  |  Views: 7

Node.js - Crypto

Prashant Surya  |   Nov 19, 2019  |  Views: 13

Node.js - Performance Hooks

Prashant Surya  |   Nov 19, 2019  |  Views: 8

Node.js - Path

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Node.js - StringDecoder

Prashant Surya  |   Nov 19, 2019  |  Views: 18

Node.js - Assertion

Prashant Surya  |   Nov 19, 2019  |  Views: 7

Node.js - Query String

Pooja Goel  |   Nov 19, 2019  |  Views: 7

Node.js - Callbacks

Prashant Surya  |   Nov 19, 2019  |  Views: 16

Node.js - Buffers

Prashant Surya  |   Nov 19, 2019  |  Views: 11

Node.js - Events

Prashant Surya  |   Nov 19, 2019  |  Views: 18

Node.js - ZLIB

Prashant Surya  |   Nov 19, 2019  |  Views: 13

Node.js - TTY

Prashant Surya  |   Nov 19, 2019  |  Views: 12

Node.js - Trace Events

Prashant Surya  |   Nov 19, 2019  |  Views: 6

Node.js - Worker Threads

Prashant Surya  |   Nov 19, 2019  |  Views: 8

Node.js - Web Modules

Prashant Surya  |   Nov 19, 2019  |  Views: 9

Want to sell your software ?-

If you want to sell your readymade software to the genuine clients or businessman, list your software with details and demo links.

  • Sell ERP
  • Sell Website Clones
  • Sell App Clones
  • Sell Readymade Portals
  • Sell Readymade Websites
  • Sell Mobile Apps
  • Sell Window Apps

Clients will find it using our advanced search filter and will contact you directly.

No any charge for the product lsiting.

Do you own a Company ?+

Property.sale

Buy or Sell Commercial Property+

Are you a freelancer ?+

Looking for a job ?+

Are you a Service Provider ?+

Are you a blogger ?+

Do you own an IT Institute ?+



Property.sale