vpd

Virtual Private Database for Rails

This is a quick gemification of the schema partitioning solution for multi-tenancy support in Rails. It is EXPERIMENTAL and currently specific to PostgreSQL.

It requires Rails 3.0.7+ and pg 0.11.0+.

The schema partitioning approach is described by Guy Naor in his definitive presentation: [confreaks.net/videos/111-aac2009-writing-multi-tenant-applications-in-rails]

What it does

patches the postgresql adapter so it is possible to run your rails migrations into a specific schema
adds helper methods for activating a selected schema

How to use it

To install, add to your Gemfile:

gem 'vpd'

and run bundle install.

Once installed, it provides a number of methods to setup and switch between schemas.

Vpd.activate(schema,verify_migration = false)

This is the main method to switch to a specified schema. If you pass true for verify_migration, it will create the schema if necessary and make sure your rails migrations (in that schema) are up-to-date.

How do you know which schema to switch to? Well, that’s up to you .. could be on the basis of the request subdomain, or the an attribute of the current_user.

e.g. we might do this in a before_filter of our ApplicationController…

# this may evaluate to 'my_company' for example ..
schema_to_use = request.subdomains.last
if schema_to_use.present?
  # now activate the schema
  Vpd.activate(schema_to_use,true)
else
  # ensure we are running with the default
  Vpd.activate_default
end

Vpd.activate_default

Returns to default schema search path. This will either be ‘“$user”,public’ (postgres default) or the schema_search_path setting from your database.yml

and a bunch of other methods #nodoc

What it doesn’t do / things to do

Provide some syntactic sugar to allow migrations to be selectively included/excluded
Genericise the approach to support other db backends
Useful tests to ensure this isn’t breaking soemthing in Rails that I haven’t noticed yet
Find a way to do this without monkey-patching
Better documentation

Contributing to vpd

Check out the latest master to make sure the feature hasn’t been implemented or the bug hasn’t been fixed yet
Check out the issue tracker to make sure someone already hasn’t requested it and/or contributed it
Fork the project
Start a feature/bugfix branch
Commit and push until you are happy with your contribution
Make sure to add tests for it. This is important so I don’t break it in a future version unintentionally.
Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

vpd