Canceling HTTP Requests in Node.js: A Step-by-Step Guide
Learn How to Abort or Cancel HTTP Requests in Node.js with Practical Examples
As a Node.js developer, you may need to make HTTP requests in Node.js to interact with other servers or APIs. However, these requests can take time to receive a response, and in some cases, you may need to cancel the request if it is taking too long or if it fails. In this article, we’ll explore how to use the Abort API in Node.js to cancel an HTTP request.
What is the Abort API?
The Abort API is a JavaScript API that provides a standard way to cancel asynchronous tasks such as an in-flight HTTP request. It consists of two classes: AbortController and AbortSignal.
The AbortController is used to create an AbortSignal instance and to send an abort signal to the associated tasks. When the AbortController’s abort() method is called, it sets the AbortSignal's aborted property to true and dispatches an abort event to the registered event listeners.
The AbortSignal is used to listen to the abort event and to handle the abort signal in the associated tasks. It has a aborted property that indicates whether the signal has been aborted.
The Abort API was first introduced in web browsers in 2017 and is now available in Node.js.
How to Use the Abort API to Cancel an HTTP Request
To use the Abort API to cancel an HTTP request in Node.js, follow these steps:
Step 1: Create an AbortController and an AbortSignal instance.
const controller = new AbortController();
const signal = controller.signal;Step 2: Make an HTTP request with the AbortSignal option.
const options = { signal };
const request = http.request(url, options, (response) => {...});Note that you can also use the https.request method or a Node.js HTTP library that supports the AbortSignal option, such as Axios.
Step 3: Register an event listener for the abort event.
signal.addEventListener('abort', () => {
console.log('The abort signal was triggered');
});Step 4: Call the AbortController’s abort() method to cancel the HTTP request.
controller.abort();If the HTTP request has not yet been sent, calling the abort() method will prevent it from being sent. If the HTTP request is in-flight, calling the abort() method will abort it and trigger the abort event.
Example: Cancel an HTTP Request After a Timeout
In this example, we’ll use the Abort API to cancel an HTTP request if it takes longer than a specified timeout. We’ll use the native fetch to make the HTTP request and the promise variant of setTimeout to create the timeout.
const { setTimeout } = require('timers/promises');
const url = 'https://jsonplaceholder.typicode.com/posts';
const timeout = 1000; // milliseconds
const controller = new AbortController();
const signal = controller.signal;
const request = fetch(url, { signal });
const timeoutPromise = setTimeout(timeout, undefined, { signal });
const racePromise = Promise.race([request, timeoutPromise]);
racePromise
.then((response) => {
console.log('HTTP request succeeded:', response);
})
.catch((error) => {
console.log('HTTP request failed:', error);
})
.finally(() => {
controller.abort();
});In this example, we first create an AbortController and an AbortSignal instance. We then make an HTTP request with the fetch and the AbortSignal option. We also create a timeout promise with the promise variant of setTimeout and pass it the AbortSignal optionas well.
We then use Promise.race to race the HTTP request and the timeout promise against each other. The racePromise will resolve with the value of the first promise that resolves or reject with the reason of the first promise that rejects.
If the HTTP request completes within the timeout, the racePromise will resolve with the HTTP response. If the HTTP request does not complete within the timeout, the timeoutPromise will abort the HTTP request and the racePromise will reject with an error.
Finally, we call the AbortController’s abort() method in the finally block to ensure that the HTTP request is cancelled regardless of whether it succeeded or failed.
Conclusion
By using the Abort API, you can gain more control over your HTTP requests and improve the reliability and performance of your Node.js applications.Remember to always use the latest version of Node.js to ensure the best support for the Abort API. Also, be aware that not all HTTP libraries and APIs in Node.js support the AbortSignal option, so check the documentation before using it.
