LTI-357: fix for making actioncable endpoint be dynamically configured (

#305)

app/controllers/rooms_controller.rb

@@ -39,6 +39,8 @@ class RoomsController < ApplicationController
   before_action :check_for_cancel, only: [:create, :update]
   before_action :allow_iframe_requests
   before_action :set_current_locale
+  before_action :set_action_cable, only: %i[launch]
+
   after_action :broadcast_meeting, only: [:meeting_end]
 
   # GET /rooms/1
@@ -492,4 +494,13 @@ def room_handler(launch_params, tenant)
 
     Digest::SHA1.hexdigest(input)
   end
+
+  def set_action_cable
+    relative_url_root = Rails.configuration.relative_url_root
+    relative_url_root = relative_url_root.chop if relative_url_root[-1] == '/'
+    config = ActionCable::Server::Configuration.new
+    config.cable = { url: "wss://#{request.host}#{relative_url_root}/rooms/cable" }
+
+    ActionCable::Server::Base.new(config: config)
+  end
 end

config/application.rb

@@ -34,7 +34,6 @@ class Application < Rails::Application
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration should go into files in config/initializers
     # -- all .rb files in that directory are automatically loaded.
-    config.url_host = ENV['URL_HOST']
 
     config.build_number = ENV['BUILD_NUMBER'] || 'v1'
 
@@ -56,8 +55,7 @@ class Application < Rails::Application
     # Mount Action Cable outside main process or domain
     relative_url_root = config.relative_url_root
     relative_url_root = relative_url_root.chop if relative_url_root[-1] == '/'
-    config.action_cable.url = "wss://#{ENV['URL_HOST']}#{relative_url_root}/rooms/cable"
-    config.action_cable.mount_path = '/rooms/cable'
+    config.action_cable.mount_path = "#{relative_url_root}/rooms/cable"
 
     # Settings for external services.
     config.cache_enabled = ENV.fetch('CACHE_ENABLED', 'false').casecmp?('true')

config/routes.rb

@@ -17,7 +17,7 @@
 #  with BigBlueButton; if not, see <http://www.gnu.org/licenses/>.
 
 Rails.application.routes.draw do
-  mount ActionCable.server => Rails.configuration.action_cable.url
+  mount ActionCable.server => '/rooms/cable'
 
   scope 'rooms' do
     get '/health_check', to: 'health_check#show'