Rails Multisite

This gem provides multi-db support for Rails applications.

Using its middleware you can partition your app so each hostname has its own db.

It provides a series of helper for working with multiple database, and some additional rails tasks for working with them.

It was extracted from Discourse. https://discourse.org


Add this line to your application's Gemfile:

gem 'rails_multisite'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rails_multisite


Configuration requires a file called: config/multisite.yml that specifies connection specs for all dbs.

  adapter: postgresql
  database: discourse_mlp
  username: discourse_mlp
  password: applejack
  host: dbhost
  pool: 5
  timeout: 5000
    - discourse.equestria.com
    - discourse.equestria.internal

  adapter: postgresql
  database: discourse_who
  username: discourse_who
  password: "Up the time stream without a TARDIS"
  host: dbhost
  pool: 5
  timeout: 5000
    - discuss.tardis.gallifrey

Execute a query on each connection

RailsMultisite::ConnectionManagement.each_connection do |db|
  # run query in context of db
  # eg: User.find(1)
RailsMultisite::ConnectionManagement.each_connection(threads: 5) do |db|
  # run query in context of db, will do so in a thread pool of 5 threads
  # if any query fails an exception will be raised
  # eg: User.find(1)

Usage with Rails

RAILS_DB Environment Variable

When working with a Rails application, you can specify the DB that you'll like to work with by specifying the RAILS_DB ENV variable.

# config/multisite.yml

  adapter: ...
  database: some_database_1

  adapater: ...
  database: some_database_2

To get a Rails console that is connected to some_database_1 database:

RAILS_DB=db_one rails console

CDN origin support

To avoid needing to configure many origins you can consider using RailsMultisite::ConnectionManagement.asset_hostnames

When configured, requests to asset_hostname?__ws=another.host.name will be re-routed to the correct site. Cookies will be stripped on all incoming requests.


  • Multisite serves sub.example.com and assets.example.com
  • RailsMultisite::ConnectionManagement.asset_hostnames = ['assets.example.com']
  • Requests to https://assets.example.com/route/?__ws=sub.example.com will be routed to the sub.example.com


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request