Use a custom method to detect the current tenant

The subdomain elevator we were using, which is included in apartment,
didn't work on hosts already including a subdomain (like
demo.consul.dev, for instance). In those cases, we would manually add
the subdomain to the list of excluded subdomains. Since these subdomains
will be different for different CONSUL installations, it meant each
installation had to customize the code. Furthermore, existing
installations using subdomains would stop working.

So we're using a custom method to find the current tenant, based on the
host defined in `default_url_options`.

In order to avoid any side-effects on single-tenant applications, we're
adding a new configuration option to enable multitenancy

We're enabling two ways to handle this configuration option:

a) Change the application_custom.rb file, which is under version control
b) Change the secrets.yml file, which is not under version control

This way people prefering to handle configuration options through
version control can do so, while people who prefer handling
configuration options through te secrets.yml file can do so as well.

We're also disabling the super-annoying warnings mentioning there are no
tenants which we got every time we run migrations on single-tenant
applications. These messages will only be enabled when the multitenancy
feature is enabled too. For this reason, we're also disabling the
multitenancy feature in the development environment by default.

app/models/tenant.rb

@@ -10,8 +10,25 @@ class Tenant < ApplicationRecord
   after_update :rename_schema
   after_destroy :destroy_schema
 
+  def self.resolve_host(host)
+    return nil unless Rails.application.config.multitenancy.present?
+    return nil if host.blank? || host.match?(Resolv::AddressRegex)
+
+    host_domain = allowed_domains.find { |domain| host == domain || host.ends_with?(".#{domain}") }
+    host.delete_prefix("www.").sub(/\.?#{host_domain}\Z/, "").presence
+  end
+
+  def self.allowed_domains
+    dev_domains = %w[localhost lvh.me example.com]
+    dev_domains + [default_host]
+  end
+
   def self.excluded_subdomains
-    Apartment::Elevators::Subdomain.excluded_subdomains + %w[mail shared_extensions]
+    %w[mail public shared_extensions www]
+  end
+
+  def self.default_host
+    ActionMailer::Base.default_url_options[:host]
   end
 
   def self.switch(...)

config/application.rb

@@ -134,6 +134,9 @@ module Consul
     config.autoload_paths << "#{Rails.root}/app/graphql/custom"
     config.autoload_paths << "#{Rails.root}/app/models/custom"
     config.paths["app/views"].unshift(Rails.root.join("app", "views", "custom"))
+
+    # Set to true to enable managing different tenants using the same application
+    config.multitenancy = Rails.application.secrets.multitenancy
   end
 end
 

config/environments/test.rb

@@ -59,6 +59,9 @@ Rails.application.configure do
       Bullet.raise = true # raise an error if n+1 query occurs
     end
   end
+
+  # Allow managing different tenants using the same application
+  config.multitenancy = true
 end
 
 require Rails.root.join("config", "environments", "custom", "test")

config/initializers/apartment.rb

@@ -2,9 +2,9 @@
 # Apartment can support many different "Elevators" that can take care of this routing to your data.
 # Require whichever Elevator you're using below or none if you have a custom one.
 #
-# require "apartment/elevators/generic"
+require "apartment/elevators/generic"
 # require "apartment/elevators/domain"
-require "apartment/elevators/subdomain"
+# require "apartment/elevators/subdomain"
 # require "apartment/elevators/first_subdomain"
 # require "apartment/elevators/host"
 
@@ -12,6 +12,7 @@ require "apartment/elevators/subdomain"
 # Apartment Configuration
 #
 Apartment.configure do |config|
+  ENV["IGNORE_EMPTY_TENANTS"] = "true" if Rails.env.test? || Rails.application.config.multitenancy.blank?
   config.seed_after_create = true
 
   # Add any models that you do not want to be multi-tenanted, but remain in the global (public) namespace.
@@ -106,12 +107,11 @@ end
 
 # Setup a custom Tenant switching middleware. The Proc should return the name of the Tenant that
 # you want to switch to.
-# Rails.application.config.middleware.use Apartment::Elevators::Generic, lambda { |request|
+Rails.application.config.middleware.use Apartment::Elevators::Generic, ->(request) do
-#   request.host.split(".").first
+  Tenant.resolve_host(request.host)
-# }
+end
 
 # Rails.application.config.middleware.use Apartment::Elevators::Domain
-Rails.application.config.middleware.use Apartment::Elevators::Subdomain
+# Rails.application.config.middleware.use Apartment::Elevators::Subdomain
 # Rails.application.config.middleware.use Apartment::Elevators::FirstSubdomain
 # Rails.application.config.middleware.use Apartment::Elevators::Host
-Apartment::Elevators::Subdomain.excluded_subdomains = %w[public www]

config/secrets.yml.example

@@ -18,6 +18,7 @@ http_basic_auth: &http_basic_auth
 development:
   http_basic_username: "dev"
   http_basic_password: "pass"
+  multitenancy: false
   secret_key_base: 56792feef405a59b18ea7db57b4777e855103882b926413d4afdfb8c0ea8aa86ea6649da4e729c5f5ae324c0ab9338f789174cf48c544173bc18fdc3b14262e4
   <<: *maps
 
@@ -48,6 +49,7 @@ staging:
   http_basic_password: ""
   managers_url: ""
   managers_application_key: ""
+  multitenancy: false
   <<: *maps
   <<: *apis
 
@@ -74,6 +76,7 @@ preproduction:
   http_basic_password: ""
   managers_url: ""
   managers_application_key: ""
+  multitenancy: false
   twitter_key: ""
   twitter_secret: ""
   facebook_key: ""
@@ -105,6 +108,7 @@ production:
   http_basic_password: ""
   managers_url: ""
   managers_application_key: ""
+  multitenancy: false
   twitter_key: ""
   twitter_secret: ""
   facebook_key: ""

spec/models/tenant_spec.rb

@@ -1,6 +1,138 @@
 require "rails_helper"
 
 describe Tenant do
+  describe ".resolve_host" do
+    before do
+      allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "consul.dev" })
+    end
+
+    it "returns nil for empty hosts" do
+      expect(Tenant.resolve_host("")).to be nil
+      expect(Tenant.resolve_host(nil)).to be nil
+    end
+
+    it "returns nil for IP addresses" do
+      expect(Tenant.resolve_host("127.0.0.1")).to be nil
+    end
+
+    it "returns nil using development and test domains" do
+      expect(Tenant.resolve_host("localhost")).to be nil
+      expect(Tenant.resolve_host("lvh.me")).to be nil
+      expect(Tenant.resolve_host("example.com")).to be nil
+      expect(Tenant.resolve_host("www.example.com")).to be nil
+    end
+
+    it "treats lvh.me as localhost" do
+      expect(Tenant.resolve_host("jupiter.lvh.me")).to eq "jupiter"
+      expect(Tenant.resolve_host("www.lvh.me")).to be nil
+    end
+
+    it "returns nil for the default host" do
+      expect(Tenant.resolve_host("consul.dev")).to be nil
+    end
+
+    it "ignores the www prefix" do
+      expect(Tenant.resolve_host("www.consul.dev")).to be nil
+    end
+
+    it "returns subdomains when present" do
+      expect(Tenant.resolve_host("saturn.consul.dev")).to eq "saturn"
+    end
+
+    it "ignores the www prefix when subdomains are present" do
+      expect(Tenant.resolve_host("www.saturn.consul.dev")).to eq "saturn"
+    end
+
+    it "returns nested additional subdomains" do
+      expect(Tenant.resolve_host("europa.jupiter.consul.dev")).to eq "europa.jupiter"
+    end
+
+    it "ignores the www prefix in additional nested subdomains" do
+      expect(Tenant.resolve_host("www.europa.jupiter.consul.dev")).to eq "europa.jupiter"
+    end
+
+    it "does not ignore www if it isn't the prefix" do
+      expect(Tenant.resolve_host("wwwsaturn.consul.dev")).to eq "wwwsaturn"
+      expect(Tenant.resolve_host("saturn.www.consul.dev")).to eq "saturn.www"
+    end
+
+    it "returns the host as a subdomain" do
+      expect(Tenant.resolve_host("consul.dev.consul.dev")).to eq "consul.dev"
+    end
+
+    it "returns nested subdomains containing the host" do
+      expect(Tenant.resolve_host("saturn.consul.dev.consul.dev")).to eq "saturn.consul.dev"
+    end
+
+    it "returns full domains when they don't contain the host" do
+      expect(Tenant.resolve_host("unrelated.dev")).to eq "unrelated.dev"
+      expect(Tenant.resolve_host("mercury.anotherconsul.dev")).to eq "mercury.anotherconsul.dev"
+    end
+
+    it "ignores the www prefix in full domains" do
+      expect(Tenant.resolve_host("www.unrelated.dev")).to eq "unrelated.dev"
+      expect(Tenant.resolve_host("www.mercury.anotherconsul.dev")).to eq "mercury.anotherconsul.dev"
+    end
+
+    context "multitenancy disabled" do
+      before { allow(Rails.application.config).to receive(:multitenancy).and_return(false) }
+
+      it "always returns nil" do
+        expect(Tenant.resolve_host("saturn.consul.dev")).to be nil
+        expect(Tenant.resolve_host("jupiter.lvh.me")).to be nil
+      end
+    end
+
+    context "default host contains subdomains" do
+      before do
+        allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "demo.consul.dev" })
+      end
+
+      it "ignores subdomains already present in the default host" do
+        expect(Tenant.resolve_host("demo.consul.dev")).to be nil
+      end
+
+      it "ignores the www prefix" do
+        expect(Tenant.resolve_host("www.demo.consul.dev")).to be nil
+      end
+
+      it "returns additional subdomains" do
+        expect(Tenant.resolve_host("saturn.demo.consul.dev")).to eq "saturn"
+      end
+
+      it "ignores the www prefix in additional subdomains" do
+        expect(Tenant.resolve_host("www.saturn.demo.consul.dev")).to eq "saturn"
+      end
+
+      it "returns nested additional subdomains" do
+        expect(Tenant.resolve_host("europa.jupiter.demo.consul.dev")).to eq "europa.jupiter"
+      end
+
+      it "ignores the www prefix in additional nested subdomains" do
+        expect(Tenant.resolve_host("www.europa.jupiter.demo.consul.dev")).to eq "europa.jupiter"
+      end
+
+      it "does not ignore www if it isn't the prefix" do
+        expect(Tenant.resolve_host("wwwsaturn.demo.consul.dev")).to eq "wwwsaturn"
+        expect(Tenant.resolve_host("saturn.www.demo.consul.dev")).to eq "saturn.www"
+      end
+    end
+
+    context "default host is similar to development and test domains" do
+      before do
+        allow(ActionMailer::Base).to receive(:default_url_options).and_return({ host: "mylvh.me" })
+      end
+
+      it "returns nil for the default host" do
+        expect(Tenant.resolve_host("mylvh.me")).to be nil
+      end
+
+      it "returns subdomains when present" do
+        expect(Tenant.resolve_host("neptune.mylvh.me")).to eq "neptune"
+      end
+    end
+  end
+
   describe "validations" do
     let(:tenant) { build(:tenant) }