Apartment

Multitenancy for Rails 3

Apartment provides tools to help you deal with multiple databases in your Rails environment. If you need to have certain data sequestered based on account or company, but still allow some data to exist in a common database, Apartment can help.

Caveats

Apartment was built to deal with a very particular use-case - the need to spin up multiple databases within the same application instance on-demand while Rails is running. If your setup can accomodate creating new databases on deploy (by adding a new database to your database.yml), or doesn't need 100% database isolation, other solutions might be far simpler for your use case.

Installation

Rails 3

Add the following to your Gemfile:

  gem 'apartment'

That's all you need to set up the Apartment libraries. If you want to switch databases on a per-user basis, look under "Usage - Switching databases per request", below.

Usage

Creating new Databases

Before you can switch to a new apartment database, you will need to create it. Whenever you need to create a new database, you can run the following command:

 Apartment::Database.create('database_name')

Apartment will create a new database in the following format: "environment_database_name". In the case of a sqlite database, this will be created in your 'db/migrate' foler. With other databases, the database will be created as a new DB within the system.

When you create a new database, all migrations will be run against that database, so it will be up to date when create returns.

Notes on PostgreSQL

PostgreSQL works slightly differently than other databases when creating a new DB. If you are using PostgreSQL, Apartment will set up a new schema and migrate into there. This provides better performance, and allows Apartment to work on systems like Heroku, which would not allow a full new database to be created.

Switching Databases

To switch databases using Apartment, use the following command:

Apartment::Database.switch('database_name')

When switch is called, all requests coming to ActiveRecord will be routed to the database you specify (with the exception of excluded models, see below). To return to the 'root' database, call switch with no arguments.

Switching Databases per request

You can have Apartment route to the appropriate database by adding some Rack middleware. Apartment can support many different "Elevators" that can take care of this routing to your data. In house, we use the subdomain elevator, which analyzes the subdomain of the request and switches to a database schema of the same name. It can be used like so:

# application.rb
module My Application
  class Application < Rails::Application

    config.middleware.use 'Apartment::Elevators::Subdomain'
  end
end

Excluding models

If you have some models that should always access the 'root' database, you can specify this by configuring Apartment using Apartment.configure. This will yield a config object for you. You can set excluded models like so:

Apartment.configure do |config|
  config.excluded_models = [User, Company]        # these models will not be multi-tenanted, but remain in the global (public) namespace
end

Managing Migrations

In order to migrate all of your databases (or posgresql schemas) you need to provide a list of dbs to Apartment. You can make this dynamic by providing a Proc object to be called on migrations. This object should yield an array of string representing each database name. Example:

# Dynamically get database names to migrate
Apartment.configure do |config|
  config.database_names = lambda{ Company.all.collect(&:database_name) }
end

# Use a static list of database names for migrate
Apartment.configure do |config|
  config.database_names = ['db1', 'db2']
end

You can then migration your databases using the rake task:

rake apartment:migrate

This basically invokes Apartment::Database.migrate(#{db_name}) for each database name supplied from Apartment.database_names

TODO

• Cross-database associations

Contributing