Introduction Post: https://www.citusdata.com/blog/2017/01/05/easily-scale-out-multi-tenant-apps/
ActiveRecord/Rails integration for multi-tenant databases, in particular the open-source Citus extension for PostgreSQL.
Enables easy scale-out by adding the tenant context to your queries, enabling the database (e.g. Citus) to efficiently route queries to the right database node.
Add the following to your Gemfile:
Supported Rails versions
All Ruby on Rails versions starting with 4.2 or newer (up to 6.0) 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 # ... 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
Rolling out activerecord-multi-tenant for your application (write-only mode)
The library relies on tenant_id to be present and NOT NULL for all rows. However, its often useful to have the library set the tenant_id for new records, and then backfilling tenant_id for existing records as a background task.
To support this, there is a write-only mode, in which tenant_id is not included in queries, but only set for new records. Include the following in an initializer to enable it:
Once you are ready to enforce tenancy, make your tenant_id column NOT NULL and simply remove that line.
Frequently Asked Questions
- 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(0) to access these objects.
- What if my tenant model is not defined in my application?
The tenant model does not have to be defined. Use the gem as if the model was present.
MultiTenant.with accepts either a tenant id or model instance.
This gem was initially based on acts_as_tenant, and still shares some code. We thank the authors for their efforts.
Copyright (c) 2018, Citus Data Inc.
Licensed under the MIT license, see LICENSE file for details.