Question

I’m actually doing some load testing against an ExpressJS server, and I noticed that the response send by the server includes a “Connection: Keep-Alive” header. As far as I understand it, the connection will remain opened until the server or the client sends a “Connection: Close” header.

In some implementations, the “Connection: Keep-Alive” header comes up with a “Keep-Alive” header setting the connection timeout and the maximum number of consecutive requests send via this connection.

For example : “Keep-Alive: timeout=15, max=100”

Is there a way (and is it relevant) to set these parameters on an Express server ?

If not, do you know how ExpressJS handles this ?

Edit:
After some investigations, I found out that the default timeout is set in the node standard http library:

socket.setTimeout(2 * 60 * 1000); // 2 minute timeout

In order to change this:

var http = require('http');

http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end("Hello World");
}).on('connection', function(socket) {
  socket.setTimeout(10000);
}).listen(3000);

Anyway it still looks a little bit weird to me that the server doesn’t send any hint to the client concerning its timeout.

Edit2:
Thanks to josh3736 for his comment.

setSocketKeepAlive is not related to HTTP keep-alive. It is a TCP-level option that allows you to detect that the other end of the connection has disappeared.

Answer 1

For Express 3:

var express = require('express');
var app = express();
var server = app.listen(5001);

server.on('connection', function(socket) {
  console.log("A new connection was made by a client.");
  socket.setTimeout(30 * 1000); 
  // 30 second timeout. Change this as you see fit.
});