Graceful shutdown of a node.JS HTTP server

Question

Here is a simple webserver I am working on

var server = require("http").createServer(function(req,resp) {
    resp.writeHead(200,{"Content-Type":"text/plain"})
    resp.write("hi")
    resp.end()
    server.close()
})
server.listen(80, 'localhost')
// The shortest webserver you ever did see! Thanks to Node.JS :)

Works great except for keep-alive. When the first request comes in, server.close gets called. But the process does not end. Actually the TCP connection is still open which allows another request to come through which is what I am trying to avoid.

How can I close existing keep-alive connections?

Answer 1

You can call request.connection.destroy() in the response callback. That will close the request connection.

It will also end your process since there is nothing left to do, the end result is the same as calling process.exit() right there.

Answer 2

You can control the idle timeout for a connection, so you can set how long a keep-alive connection will remain open. For example:

server=require('http').createServer(function(req,res) {
    //Respond
    if(req.url.match(/^\/end.*/)) {
        server.close();
        res.writeHead(200,{'Content-Type':'text/plain'});
        res.end('Closedown');
    } else {
        res.writeHead(200,{'Content-Type':'text/plain'});
        res.end('Hello World!');
    }
}).listen(1088);
//Set the idle timeout on any new connection
server.addListener("connection",function(stream) {
    stream.setTimeout(4000);
});

We can test this with netcat:

ben@quad-14:~/node$ echo -e "GET /test HTTP/1.1\nConnection: keep-alive\n\n" | netcat -C -q -1 localhost 1088
HTTP/1.1 200 OK
Content-Type: text/plain
Connection: keep-alive
Transfer-Encoding: chunked

c
Hello World!
0

after 4 seconds, the connection closes

And now we can show that closing the server works: after all idle connections are dropped, the server exits:

ben@quad-14:~/node$ echo -e "GET /end HTTP/1.1\nConnection: keep-alive\n\n" | netcat -C -q -1 localhost 1088
HTTP/1.1 200 OK
Content-Type: text/plain
Connection: keep-alive
Transfer-Encoding: chunked

9
Closedown
0

after 4 seconds, the connection closes and the server exits

Answer 3

If you're closing the server as part of a graceful shutdown of the process, you just need this:

var server = require('http').createServer(myFancyServerLogic);

server.on('connection', function (socket) {socket.unref();});
server.listen(80);

function myFancyServerLogic(req, res) {
    req.connection.ref();

    res.end('Hello World!', function () {
        req.connection.unref();
    });
}

Basically, the sockets that your server uses will only keep the process alive while they're actually serving a request. While they're just sitting there idly (because of a Keep-Alive connection), a call to server.close() will close the process, as long as there's nothing else keeping the process alive. If you need to do other things after the server closes, as part of your graceful shutdown, you can hook into process.on('beforeExit', callback) to finish your graceful shutdown procedures.