Forward HTTP RESTfull API requests from http server to my application

Question

I have a question about the design of an application I'm working on.

I made a monolithic java application with sockets open 24/7, something like a game server. I'm just trying to say it's a single jar application instead of a modular servlet/page based web application.

I would now like to add a RESTful API to this application. So people/clients can make HTTP requests to my application to obtain certain info. Because of the monolithic nature of my java application I'm unsure of how to implement this. One other important thing: I'm expecting multiple requests per second, so it would be nice if I could have an existing http server handle the requests, and somehow forward them to my app to set up a reply, and have the http server send it again.

Some things I have thought of:

• wrap my application in a tomcat application, although I'm not sure if tomcat can run an application continuously instead of mapping to servlets on request.

• open a socket and parse incoming http requests myself (or there is propably a lib for that?). I fear this will have an impact on performance, and would rather use existing http servers because they are optimized for high traffic.

• use an excisting http server to handle the requests (apache, lighttp, ...) and have it forward requests to my app via things like scgi, or use a server that can forward via XMLRPC. Are there any other technologies/protocols to do this?

Any advice on how to handle this? Thanks!

Answer 1

I'd decouple your RESTful service endpoint as much as possible from your original application. This allows you to scale (add multiple servers for your REST endpoint), but also to change your original application without having to change your REST API directly.

Clients <== REST (HTTP) ==> RESTful endpoint <== legacy (sockets) ==> Legacy backend

So your REST server is one the hand a service provider for your clients, but represents at the same time also a client for your original backend.

I would design the RESTful API and then pick one of the existing REST frameworks for Java, like Restlet, and implement the REST service itself. At the same time you can start implementing a gateway between the REST server and your original backend, by using sockets.

Pay attention to scalability and performance (i.e. you may want to use connection pools for the rest <=> backend bridge and not spawn a socket per incoming API request) and also think of possible advantages of HTTP. You might benefit when you're able to use caching, etc. as far as your backend application logic allows so.