Multitenancy

Multitenancy is a very talked-about subject. We're not going to go very deep into how to achieve it on the database level, but will talk a little bit about how it's supported in Avo.

Breakdown

Usually, with multitenancy you add a new layer just one level below authentication. You don't have just a user to think about, but now that user might act on the behalf of a tenant. That tenant can be an Account or a Team, or any other model you design in your database.

So now, the mission is to pinpoint which tenant is the user acting for. Because Avo has such an integrated experience and we use our own ApplicationController, you might think it's difficult to add that layer, when in fact it's really not. There are a couple of steps to do.

Avo ships two attributes on Avo::Current — tenant_id and tenant — that are left empty for you to populate. There's no dedicated config option; you set them yourself in a before_action, and everything below is a recipe for doing that.

INFO

We'll use the foo tenant id from now on.

Route-based tenancy

There are a couple of strategies here, but a common one is to use route-based tenancy. That means that your user uses a URL like https://example.com/foo/ and the app should know to scope everything to that foo tenant.

We need to do a few things:

1. Set the proper routing pattern

Mount Avo under the tenant_id scope

# config/routes.rb
Rails.application.routes.draw do
  scope "/:tenant_id" do
    mount_avo
  end
end

2. Keep the tenant in every generated URL

Because Avo mounts under /:tenant_id, every path Avo generates needs that segment or the links will drop the tenant and break. Add tenant_id to default_url_options so Avo appends it automatically.

# config/initializers/avo.rb
Avo.configure do |config|
  config.default_url_options = [:tenant_id]
end

3. Set the tenant for each request

config/initializers/avo.rb

Avo.configure do |config|
  # configuration values
end

Rails.configuration.to_prepare do
  Avo::ApplicationController.include Multitenancy
end

app/controllers/concerns/multitenancy.rb

module Multitenancy
  extend ActiveSupport::Concern

  included do
    prepend_before_action :set_tenant
  end

  def set_tenant
    Avo::Current.tenant_id = params[:tenant_id]
    Avo::Current.tenant = Account.find params[:tenant_id]
  end
end

Now, whenever you navigate to https://example.com/foo the tenant_id will be set to foo.

Session-based tenancy

Using a session-based tenancy strategy is a bit simpler as we don't meddle with the routing.

WARNING

The code below shows how it's possible to do session-based multitenancy but your use-case or model names may vary a bit.

We need to do a few things:

1. Set the tenant for each request

config/initializers/avo.rb

Avo.configure do |config|
  # configuration values
end

Rails.configuration.to_prepare do
  Avo::ApplicationController.include Multitenancy
end

app/controllers/concerns/multitenancy.rb

module Multitenancy
  extend ActiveSupport::Concern

  included do
    prepend_before_action :set_tenant
  end

  def set_tenant
    Avo::Current.tenant = Account.find(session[:tenant_id] || current_user.accounts.first.id)
  end
end

2. Add an account switcher

Add a route for the switcher, a controller to update the session, and a view to render the links.

config/routes.rb

Rails.application.routes.draw do
  put "switch_account/:id", to: "avo/switch_accounts#update", as: :switch_account
end

app/controllers/avo/switch_accounts_controller.rb

class Avo::SwitchAccountsController < Avo::ApplicationController
  def update
    # set the new tenant in session
    session[:tenant_id] = params[:id]

    redirect_back fallback_location: root_path
  end
end

app/views/avo/_session_switcher.html.erb

<% current_user.accounts.each do |account| %>
  <%= link_to account.name, switch_account_path(account.id), class: class_names({"underline": session[:tenant_id].to_s == account.id.to_s}), data: {turbo_method: :put} %>
<% end %>

See also

• Avo::Current — the tenant_id and tenant attributes you populate.
• Integrate with Acts As Tenant — subdomain / row-level multitenancy using the acts_as_tenant gem.