Closing database connection in Express 3
express, node.js
Solution
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
Problem
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); }); ```