Closing database connection in Express 3

Question

In Express 3, how do you handle closing database connections when the process exists?

The .on('close', ... event is not emitted unless you explicitly use a HTTP server's .close() call.

So far, this is the closest I've come, but it uses process.on instead of server.on:

process.on('SIGTERM', function () {
   // Close connections.
   process.exit(0);
});

Answer 1

Based on the info from:

• https://github.com/visionmedia/express/issues/1366
• http://blog.argteam.com/coding/hardening-node-js-for-production-part-3-zero-downtime-deployments-with-nginx/

--

var express = require('express');

var app = express();
var server = app.listen(1337);
var shutting_down = false;

app.use(function (req, resp, next) {
 if(!shutting_down)
   return next();

 resp.setHeader('Connection', "close");
 resp.send(503, "Server is in the process of restarting");
 // Change the response to something your client is expecting:
 //   html, text, json, etc.
});

function cleanup () {
  shutting_down = true;
  server.close( function () {
    console.log( "Closed out remaining connections.");
    // Close db connections, other chores, etc.
    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);

The Connection: close header is used to tell any keep-alive connection to close the next time they send a HTTP request. More info here: http://www.jmarshall.com/easy/http/#http1.1s4

I have no idea if there are other ways of closing the keep-alive connection. The node process will hang unless the keep-alive connections are closed. The default idle timeout is 2 mins. More info. on node.js keep-alive timeouts (including on changing the timeout): How to set the HTTP Keep-Alive timeout in a nodejs server