How to run multiple Rails versions for a single website / project?

Question

I've inherited a Rails 3.2 production environment which is 'humming' away nicely.

The client now wants another major piece of work doing but I want to do it in Rails 5. The web address would be the same for both the old site and the new project. The new project would be additional functionality which would be accessed via the old site.

Any one know of a way of keeping the old site running whilst I develop and deliver the new work via Rails 5? Eventually if this all works then I get the opportunity to migrate the old site to Rails 5. However for the moment I need to serve up both Rails 3.2 and Rails 5 from the same site.

Answer 1

Personally I wouldn't touch that old app and its server, especially if the client is happy. Deploying the new app to a new server or a container service like heroku is something you should consider.

Answer 2

It's possible to do what you describe with a reverse proxy, e.g. nginx, configured to serve from different web servers based on different paths on the same host. This answer has some details on how to do that. We would need to know how your website is hosted in order to give more details on exactly how to do that.

However, there are other concerns that come up when you start separating your apps which you may not have considered. For example, if your website allows users to log in, do you want them to still be logged in when they visit the new site? To do so transparently will require sharing the session cookie, which this post describes a bit (you'll need to use the same secret key for both apps, or use a remote session store like Memcached). I'm not sure if it'll work properly when shared between Rails 3.2 and 5, though.

As a final note, breaking up your monolithic app into a distributed system is never a decision to take lightly. It would likely end up being less work, and less overall architectural overhead, to simply invest the time in upgrading from 3.2 -> 4.0 -> 4.2 -> 5.0.