ActiveRecord/Rails integration for multi-tenant databases, in particular the Citus extension for PostgreSQL.

Add the following to your Gemfile:

gem 'activerecord-multi-tenant'

All Ruby on Rails versions starting with 3.2 or newer are supported.

This gem only supports ActiveRecord (the Rails default ORM), and not alternative ORMs like Sequel.

It is required that you add multi_tenant definitions to your model in order to have full support for Citus, in particular when updating records.

In the example of an analytics application, sharding on customer_id, annotate your models like this:

class PageView < ActiveRecord::Base
  multi_tenant :customer
  belongs_to :site

  # ...
end

class Site < ActiveRecord::Base
  multi_tenant :customer
  has_many :page_views
  belongs_to :customer

  # ...
end

and then wrap all code that runs queries/modifications in blocks like this:

customer = Customer.find(session[:current_customer_id])
# ...
MultiTenant.with(customer) do
  site = Site.find(params[:site_id])
  site.update! last_accessed_at: Time.now
  site.page_views.count
end

Inside controllers you can use a before_action together with set_current_tenant, to set the tenant for the current request:

class ApplicationController < ActionController::Base
  set_current_tenant_through_filter # Required to opt into this behavior
  before_action :set_customer_as_tenant

  def set_customer_as_tenant
    customer = Customer.find(session[:current_customer_id])
    set_current_tenant(customer)
  end
end

In case you use Ruby on Rails together with Citus, please also note the following.

You'll need to disable prepared_statements in your database.yml like this:

default: &default
  adapter: postgresql
  url: <%= ENV['DATABASE_URL'] %>
  prepared_statements: false

• What if I have a table that doesn't relate to my tenant? (e.g. templates that are the same in every account)

  We recommend not using activerecord-multi-tenant on these tables. In case only some records in a table are not associated to a tenant (i.e. your templates are in the same table as actual objects), we recommend setting the tenant_id to 0, and then using MultiTenant.with_id(0) to access these objects.

This gem was initially based on acts_as_tenant, and still shares some code. We thank the authors for their efforts.

Licensed under the MIT license
Copyright (c) 2016, Citus Data Inc.