Shared models between two Rails apps - what is the ideal solution for Workflow?

Question

I am currently working on a Rails 3 project that is divided up into four parts:

• The public facing website
• The administration website/backend
• The models
• The API for third party data access

As the models are shared between the three key components I want to keep them away from being in one main project, however each part needs access to the models, but I don't want to repeat the code and have different versions everywhere.

Currently I have the model code in a gem, and in each project's Gemfile I am referencing them with the following line:

gem "my_models", :path => "../my_models/"

However when I deploy to our test servers for my co-workers to evaluate the system on I need to pull the models from an external repository, so I swap out the above line with the following:

gem "my_models", :git => "[email protected]:username/my_models.git"

This in its self works well, but its quite clunky in terms of 'versions' (i.e. I need to bump the version every time I wish to deploy the changes to the test servers), switch the line over to use git instead of local, and make sure that I'm pushing the files properly.

Previously I was using a shared git submodule, but this was just as awkward.

I would rather not build everything into one mega-project, as these tend to become monstrous and difficult to maintain, and I would also like to separate concerns if possible, so any changes I make to the administration site doesn't have much of a chance to impact the other components - obviously the models have the potential to cause issues, but that is a risk I have considered and understand.

What would people out there suggest when it comes to something like this? Or, am I going about it completely the wrong way?

Some additional background:

This app is a rewrite of an existing website which followed the model of 'lump everything into the one project' - unfortunately there are two issues here:

1. The app was badly developed - I inherited this project and when I first picked it up the load times were ~2 minutes per page with a single user - this has since been reduced but still has issues throughout
2. We are currently at our capacity limit of the current site and we anticipate that we will need to take on more load in the next 6 months - however scaling out with an 'all in one' app means we'll be wasting resources on scaling out the back end of the site which doesn't need it.

Essentially there are two things I want to separate - the Front end (being the public website and the API) and the back end - everything I know about software development tells me that combining all this together is not an ideal solution (and past history shows me that splitting these two is a good move in terms of ensuring front end performance).

Perhaps I need to look at this from another angle - keep the models in each project, and instead of sharing them between projects have a cut-down subset of functionality for each functional area (i.e. the backend needs to know who created a post, but the front end doesn't really care about that, so omit that logic when reading in the model).

Answer 1

drop the models project(put models into one of other parts, i'd suggest whatever you consider "more important"), put all projects into single repository(separate project folders) and make symlinks to models/libs/apis/whatever

your code is highly coupled together and you often need to make changes to few projects at once(like updating models and updating APIs that use them, etc)

one nice thing about single-repo-symlink setup is that your commits will be less fragmented and will usually represent full feature implementation - easier to track bugs, read history and maintain codebase

also when you deploy you don't need to read from many repositories - one less point of failure right there

release process is also simpler with such model as branch will now hold the scope of all projects

there are some drawbacks like symlinks dont work that well on windows and whatnot but for me it works perfectly

Answer 2

You can create a mountable engine that contains the shared models and create a gem out of it. This will handle the name spacing issues elegantly. Other nice aspect here is you get to share your assets also.

Watch this railscast for more details.