Simple Multitenancy in Rails

In this post, I would like to share a few snippets on how to use concerns in Rails to share some basic reusable multi-tenant patterns.

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Multi-tenancy is a common problem to solve in todays cloud-first world. The core part to a Multitenant Architecture is a "Tenant". A Tenant can be anything - a Store(Shopify), an Account(org using a SaaS product) or even a User - and typically, has data partitioned in associated tables or databases.
For heavy multi-tenant feature-set or functionality, there are many community driven gems available. You can find the complete list on ruby-toolbox. For smaller projects or learning exercises, I would rather recommend building the system on your own. It gives you clarity and greater understanding of the framework itself.
Below, is a simple concern that can get you started on making your apps multi-tenant by design. All models that include the below concern will be multi-tenant by default.

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This bring me to the second pattern. One might think what could Tenant.current mean. In any application involving tenants or users, you are most likely to set a global context of the user who is responsible for the current execution - most likely the currently signed in user. 
Typically for rails developers, this involves setting and accessing the current_user in the Thread context like Thread.current[current_user]. If you were to extend this behaviour to more actors or objects like a tenant, this can be abstracted into a useful pattern and reuse the concern.

Upon including the above concern in a model, you get 3 methods by default. An instance level make_current method to set the loaded object as current in context. Next are class level current and reset_current methods. The former returns the currently set object and the latter resets it.

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The creator pattern which tags the current user as the creator of the object being created.

Typical use-cases of this is to map entity creation with users for auditing or logging purposes.

Comments

[rhs0112]

Thanks for posting this. Could you also provide on example (of a model) that uses this concern to ensure multi tenancy?

[Ritikesh]

Hey, Thanks for reading. You can easily include the concerns and use them as you go. For eg.)

If you have a user class that you want to make current'able, add the following code:

# app/models/user.rb

class User < ActiveRecord::Base
  include ActsAsCurrent
end

# app/helpers/application_helper.rb

class ApplicationHelper
  def current_user
    return User.current if User.current
    User.find(session[:id]).make_current
  end
end

# app/controllers/application_controller.rb

class ApplicationController < ActionController::Base

  after_filter :reset_current_user

  private
  def reset_current_user
    User.reset_current
  end
end