Express.js app not shutting down cleanly with server.close()

Question

I'm trying to properly close a MongoDB connection when the app is shut down. Here is the code:

var express = require('express')
  , http = require('http')
  , mongoose = require('mongoose')
  , path = require('path');

var app = express();

app.set('port', process.env.PORT || 3000);

mongoose.connect('mongodb://localhost/test');

// some post and get handlers etc. (removed for shorter output)

var server = app.listen(app.get('port'), function(){
    console.log('Express server listening on port ' + app.get('port'));
});

function cleanup () {
    server.close(function () {
        console.log("Closed out remaining connections.");
        mongoose.connection.close();
        process.exit();
    });

    setTimeout( function () {
        console.error("Could not close connections in time, forcing shut down");
        process.exit(1);
    }, 30*1000);
}

process.on('SIGINT', cleanup);
process.on('SIGTERM', cleanup);

All is well and works when the app starts for the first time. When I hit Ctrl-c right after it has started, it cleanly shuts down with the Closed out remaining connections. message. However, as soon as the app interacts with the database or even serves a static page, and I try to shut it down after that, it exits with the following error:

net.js:1225
    throw new Error('Not running');
          ^
Error: Not running
    at Server.close (net.js:1225:11)
    at process.cleanup (<...>/app.js:77:12)
    at process.EventEmitter.emit (events.js:92:17)
    at Signal.wrap.onsignal (node.js:756:46)
22 Aug 15:15:28 - [nodemon] exiting

Any ideas what is causing this error and how I could fix it?

Answer 1

When server.close is called, there are two properties that are checked.

   handle<tcp handle>
   connections

Responsible code fragment of server.close responsible for this error;

  if (!this._handle) {
    // Throw error. Follows net_legacy behaviour.
    throw new Error('Not running');
  }

Only if handle===null and connections ===0 that the callback passed to close is called.

Case : Server is started and sent the signal with no serving.

Before close is called;

  handle === TCP handle.
  connection===0;

After close handle===null; connection===0;

The callback gets called.

Case : Server is started and sent the signal after a request server.

Before close is called;

  handle === TCP.handle;
  connection===1;

After close handle === null; connection===1;

No callback is fired.

Second time when you press ctrl-c

Before close is called;

  handle === null;
  connection===1;

since handle===null , the check throws the error you are seeing.

Answer 2

The reason your server has open connections is because you are sending Connection: keep-alive header.

Morgan's answer closes all the connections on the server cleanly, disconnecting all of the clients.

If you are just testing your application and want to shut it down cleanly before/after tests I recommend sending Connection: close header and server.close() will work as expected.