Can two Rails versions use one database?

rubyonrails-talk
1

I’m working on a Rails 1 application. We’d like to upgrade it to Rails 3 or 4, but Rails 1 is so old that we think it would take a total rewrite to upgrade. There are management and budget issues with a total rewrite. We wouldn’t be able to deliver anything until the entire rewritten application was finished.

So, we are searching for creative solutions to the upgrade problem. One idea is to start rewriting the application in Rails 4 and run it alongside the Rails 1 application. As features are added to the Rails 4 version, the same feature in the Rails 1 version could be taken offline. Users would see a mix of the two versions. Some pages would be served by Rails 1 and others by Rails 4.

This would require both the Rails 1 and Rails 4 versions to use the same database.

So my question is, will this work? What problems with this approach should we be anticipating? We know it isn’t a perfect solution, but we’re hoping it’s good enough to drive the project forward.

2

You may want to watch this talk, from last year's Railsconf. Rails Conf 2013 Changing the wheels on the bus at 80 mph: Upgrading to Rails 3 - YouTube Now this isn't moving quite as far as you want to go, but it still might be instructional.

Walter

3

The thing to consider most carefully is how you will be able to run the single website from two different rails apps. Things like linking between them, sharing authentication, session variables like session and flash, stuff like that. Databases are inherently multi-user systems so you’re not so likely to run into problems with the database itself unless you are using sqlite, although I’m not so familiar with Rails 1 ActiveRecord mechanisms anymore.

4

Thanks Walter and Jim for your feedback. The Railsconf talk was indeed informative, although we are still leaning against an upgrade path and are more likely to choose a rewrite-based approach. Jim, I hadn’t thought about the flash, so thanks for pointing that out. I think we can probably manage by limiting flash feedback to one site or the other. We might have to make some workflows slightly more complicated for that to work.

Russ

5

Russ Dast wrote in post #1135683:

Thanks Walter and Jim for your feedback. The Railsconf talk was indeed informative, although we are still leaning against an upgrade path and are more likely to choose a rewrite-based approach. Jim, I hadn't thought about the flash, so thanks for pointing that out. I think we can probably manage by limiting flash feedback to one site or the other. We might have to make some workflows slightly more complicated for that to work.

I think the point was you'll need to deal with session sharing as a whole. The flash is really just stored in the session anyway, so if you solve the session issue then you solve the flash issue along with it.