Async Hooks API in Node.js
Introduction:
Async Hooks API in Node.js provides an asynchronous API to track the lifetime of multiple asynchronous resources simultaneously. In this blog post, we’ll discuss what the Async Hooks API is, how it works, and how to use it in your own code.
Node.js Async Hooks:
The Async Hooks API is a set of functions to track the lifetime of multiple asynchronous resources. It allows developers to track the state of each asynchronous resource, receive notification of when a resource is created or destroyed, and execute custom logic each time a resource is created or destroyed.
The Async Hooks API is built on top of Node.js’ event loop, which is responsible for executing JavaScript code in an asynchronous manner. As a result, the Async Hooks API gives developers the ability to execute arbitrary code after an asynchronous resource has been created or destroyed.
Async Hooks API Usage:
The Async Hooks API can track the lifetime of multiple asynchronous resources. For example, if We have an application that makes HTTP requests. We can use the Async Hooks API to track the lifetime of each request.
You can also use the Async Hooks API to monitor when a resource is created or destroyed. Which can be useful for debugging purposes or for measuring the performance of your application.
The Async Hooks API can execute custom logic each time a resource is created or destroyed. This can perform tasks such as logging or counting the number of resources that have been created or destroyed.
Async Hooks API with Code Example:
The following example shows how to use the Async Hooks API to track the lifetime of an HTTP request. We first create an async_hooks instance and then specify the init and destroy functions. The init function will be called each time a new resource is created, and the destroy function will be called each time a resource is destroyed.
const async_hooks = require('async_hooks');
const hook = async_hooks.createHook(
{init: (asyncId, type, triggerAsyncId, resource) => {console.log(`Resource created with asyncId: ${asyncId}`);},
destroy: (asyncId) => {console.log(`Resource destroyed with asyncId: ${asyncId}`);
}
});
hook.enable();
In this example, we have created an async_hooks instance and specified the init and destroy functions. The init function will be called each time a new resource is created, and the destroy function will be called each time a resource is destroyed.
Next, we make an HTTP request using the request module. This will trigger the init function, which will print a message to the console that a new resource has been created with the given asyncId.
Finally, when the request is finished, the destroy the function will be called, which will print a message to the console that the resource has been destroyed with the given asyncId.
In this way, the Async Hooks API in Node.js allows developers to track the lifetime of multiple asynchronous resources simultaneously. It provides us with the ability to track the state of each asynchronous resource.
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