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Node.js — Fix „Socket Hang Up“ Errors

Node.js published the first release of version 19.0.0 on October 18th, 2022. After that, we updated some of the Supercharge packages to run tests for Node.js 19 to ensure compatibility of the packages.

One hiccup we noticed were the test runs for the @supercharge/sttp package. Sttp is our Http client providing a pleasant developer experience. Yet, when testing on Node.js 19 we always ran into a „Socket Hang Up“ error.

This tutorial shows you how to fix these errors!

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Fixing the „Socket Hang Up“ Errors in Node.js (v19)

The failing tests in the Sttp package were only on Node.js 19. There must be a change in in the Node.js 19.x release line that causes the socket hang up issues.

And the change is that starting from Node.js 19 the HTTP server uses HTTP(S)/1.1 Keep-Alive by default. This sets the keepAlive setting of the HTTP server to true which means outgoing HTTP(S) connections automatically use HTTP 1.1 Keep-Alive with a timeout of 5 seconds.

The keep-alive is related to our tests running into „socket hang up“ issues because we expected the HTTP connection to be closed after using it. But keeping the connection alive would cause issues with our testing setup.

Close Connections on Your HTTP Server

You can configure your Node.js HTTP server to not keep connections alive by providing the keepAlive option when creating your server instance:

import { createServer } from 'node:http'

const server = createServer({ keepAlive: false }, (req, res) => {  
  //
})

Close Connections Using the Connection Header

You may close HTTP connections using the Connection: 'close' header with your requests or responses. Clients may send the header or you append this header to the response: 

// close connections from client
import { Sttp } from '@supercharge/sttp'

const response = await Sttp  
  .withHeaders({ Connection: 'close' })
  .get('http://localhost:3000/base-url')


// close connections with the server response
import { createServer } from 'node:http'

const server = createServer({ keepAlive: false }, (req, res) => {  
  res.setHeader('Connection', 'close')
  res.end('Request handled :)')
})

Change the Keep-Alive Timeout

In case you want the keep-alive functionality to stay enabled, you can adjust the timeout value. Assign your timeout value in milliseconds to the Node.js HTTP server instance:

import { createServer } from 'node:http'

const server = createServer((req, res) => {  
  //
})

// change the keep-alive timeout to 3 seconds
server.keepAliveTimeout = 3000

Enjoy keep-alive connections in Node.js!

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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