CODEWITHSUNDEEP
mysqlnode.jsarchitecture
user2009750
user2009750

Reputation: 3187

How to keep server and application separate

I have a nodejs Application running on server with node-mysql and express, At first I faced problem where some exceptions were not handled and the application would go down with network connectivity issues.

I handled all uncaught exceptions and the sever wouldn't go down this time but instead it would hang. I figured it was because I returned response only if query didn't raise any exception, so I handled all query related exceptions too.

Next if MySQL server terminate connection for some reason my application wouldn't reconnect, i tried reconnecting but it would give an error related to "enqueue connection handshake or something". From another stack question I was supposed to use connection pool so if server terminates connection it will regain connectivity some how, which I did.

My here question is that each time I faced an issue I had to shut down whole application and thanks to nodejs where server is configured programmatically goes down too. Can I or better yet how can I decouple my Server and Application almost completely so that if I make some change in my application I wouldn't have to re-deploy?

Specially for case that right now everything is okay and my application is constantly giving me connection pool error on server and in development version its working fine, so even if I restart my application I am not sure how will I face this problem again so I can properly diagnose this.

Let me know if anyone needs more info regarding my question.

Upvotes: 0

Views: 57

Answers (1)

Stephen Wright
Stephen Wright

Reputation: 2956

Are you using a front-end framework to serve your application, or are you serving it all from server calls?

So fundamentally, if your server barfs for any reason (i.e. 500 error), you WANT to shut down and restart, because once your server is in that state, all of your in-transit data and your stack is in an unknown state. There's no way to correctly recover from that, so you are safer from both a server and an end-user point of view to shutdown the process and restart.

You can minimise the impact of this by using something like Node's Cluster module, which allows you to fork child processes of your server and generate multiple instances of the same server, connected to the same database, allowing access on the same port etc, therefore, if your user (or your server), manages to hit an unhandled exception, it can kill the process and restart without shutting down your entire server.

Edit: Here's a snippet:

var cluster = require('cluster');
var threads = require('os').cpus().length;


if(cluster.isMaster) {
    for(var i = 0; i < threads; i++) {
        cluster.fork();
    }

    cluster.on('exit', function(dead, code, signal) {
        console.log('worker ' +dead.process.pid+ ' died.');
        var worker = cluster.fork();
        console.log('worker '+worker.process.pid+ ' started');
    });

} else {
    //
    // do your server logic in here
}

That being said, there's no way for you to run up your application and server separately if Node is serving your client content. Once you terminate your server, your Endpoints are down. If you really wanted to be able to keep a client-side application active and reboot your server, you'd have to entirely separate the logic, i.e. have your Application in a different project to your server, and use your server as API endpoints only.

As for Connection Pools in Node-mysql: I have never used that module so I couldn't say what best practice is there.

Upvotes: 1

Related Questions