Allow ActionCable in-app mode

Adds an option in gitlab.yml to run ActionCable in in-app mode

Connection pool settings are also adjusted to account for the extra
threads

config/application.rb

@@ -17,10 +17,6 @@ module Gitlab
   class Application < Rails::Application
     require_dependency Rails.root.join('lib/gitlab')
     require_dependency Rails.root.join('lib/gitlab/utils')
-    require_dependency Rails.root.join('lib/gitlab/redis/wrapper')
-    require_dependency Rails.root.join('lib/gitlab/redis/cache')
-    require_dependency Rails.root.join('lib/gitlab/redis/queues')
-    require_dependency Rails.root.join('lib/gitlab/redis/shared_state')
     require_dependency Rails.root.join('lib/gitlab/current_settings')
     require_dependency Rails.root.join('lib/gitlab/middleware/read_only')
     require_dependency Rails.root.join('lib/gitlab/middleware/basic_health_check')
@@ -262,17 +258,6 @@ module Gitlab
       end
     end
 
-    # Use caching across all environments
-    # Full list of options:
-    # https://api.rubyonrails.org/classes/ActiveSupport/Cache/RedisCacheStore.html#method-c-new
-    caching_config_hash = {}
-    caching_config_hash[:redis] = Gitlab::Redis::Cache.pool
-    caching_config_hash[:compress] = Gitlab::Utils.to_boolean(ENV.fetch('ENABLE_REDIS_CACHE_COMPRESSION', '1'))
-    caching_config_hash[:namespace] = Gitlab::Redis::Cache::CACHE_NAMESPACE
-    caching_config_hash[:expires_in] = 2.weeks # Cache should not grow forever
-
-    config.cache_store = :redis_cache_store, caching_config_hash
-
     config.active_job.queue_adapter = :sidekiq
 
     # This is needed for gitlab-shell

config/gitlab.yml.example

@@ -1070,6 +1070,9 @@ production: &base
 
   ## ActionCable settings
   action_cable:
+    # Enables handling of ActionCable requests on the Puma web workers
+    # When this is disabled, a standalone ActionCable server must be started
+    in_app: true
     # Number of threads used to process ActionCable connection callbacks and channel actions
     # worker_pool_size: 4
 

config/initializers/1_settings.rb

@@ -726,6 +726,7 @@ Settings.webpack.dev_server['port']    ||= 3808
 # ActionCable settings
 #
 Settings['action_cable'] ||= Settingslogic.new({})
+Settings.action_cable['in_app'] ||= false
 Settings.action_cable['worker_pool_size'] ||= 4
 
 #

config/initializers/7_redis.rb

+# Use caching across all environments
+# Full list of options:
+# https://api.rubyonrails.org/classes/ActiveSupport/Cache/RedisCacheStore.html#method-c-new
+caching_config_hash = {}
+caching_config_hash[:redis] = Gitlab::Redis::Cache.pool
+caching_config_hash[:compress] = Gitlab::Utils.to_boolean(ENV.fetch('ENABLE_REDIS_CACHE_COMPRESSION', '1'))
+caching_config_hash[:namespace] = Gitlab::Redis::Cache::CACHE_NAMESPACE
+caching_config_hash[:expires_in] = 2.weeks # Cache should not grow forever
+
+Gitlab::Application.config.cache_store = :redis_cache_store, caching_config_hash
+
 # Make sure we initialize a Redis connection pool before multi-threaded
 # execution starts by
 # 1. Sidekiq

config/initializers/action_cable.rb

@@ -3,9 +3,9 @@
 require 'action_cable/subscription_adapter/redis'
 
 Rails.application.configure do
-  # We only mount the ActionCable engine in tests where we run it in-app
-  # For other environments, we run it on a standalone Puma server
-  config.action_cable.mount_path = Rails.env.test? ? '/-/cable' : nil
+  # Mount the ActionCable engine when in-app mode is enabled
+  config.action_cable.mount_path = Gitlab.config.action_cable.in_app ? '/-/cable' : nil
+
   config.action_cable.url = Gitlab::Utils.append_path(Gitlab.config.gitlab.relative_url_root, '/-/cable')
   config.action_cable.worker_pool_size = Gitlab.config.action_cable.worker_pool_size
 end

lib/gitlab/runtime.rb

@@ -37,7 +37,7 @@ module Gitlab
       end
 
       def puma?
-        !!defined?(::Puma) && !defined?(ACTION_CABLE_SERVER)
+        !!defined?(::Puma)
       end
 
       # For unicorn, we need to check for actual server instances to avoid false positives.
@@ -70,11 +70,11 @@ module Gitlab
       end
 
       def web_server?
-        puma? || unicorn? || action_cable?
+        puma? || unicorn?
       end
 
       def action_cable?
-        !!defined?(ACTION_CABLE_SERVER)
+        web_server? && (!!defined?(ACTION_CABLE_SERVER) || Gitlab.config.action_cable.in_app)
       end
 
       def multi_threaded?
@@ -82,19 +82,21 @@ module Gitlab
       end
 
       def max_threads
-        main_thread = 1
+        threads = 1 # main thread
 
-        if action_cable?
-          Gitlab::Application.config.action_cable.worker_pool_size
-        elsif puma?
-          Puma.cli_config.options[:max_threads]
+        if puma?
+          threads += Puma.cli_config.options[:max_threads]
         elsif sidekiq?
           # An extra thread for the poller in Sidekiq Cron:
           # https://github.com/ondrejbartas/sidekiq-cron#under-the-hood
-          Sidekiq.options[:concurrency] + 1
-        else
-          0
-        end + main_thread
+          threads += Sidekiq.options[:concurrency] + 1
+        end
+
+        if action_cable?
+          threads += Gitlab.config.action_cable.worker_pool_size
+        end
+
+        threads
       end
     end
   end

spec/lib/gitlab/runtime_spec.rb

@@ -48,18 +48,45 @@ describe Gitlab::Runtime do
     before do
       stub_const('::Puma', puma_type)
       allow(puma_type).to receive_message_chain(:cli_config, :options).and_return(max_threads: 2)
+      stub_config(action_cable: { in_app: false })
     end
 
     it_behaves_like "valid runtime", :puma, 3
+
+    context "when ActionCable in-app mode is enabled" do
+      before do
+        stub_config(action_cable: { in_app: true, worker_pool_size: 3 })
+      end
+
+      it_behaves_like "valid runtime", :puma, 6
+    end
+
+    context "when ActionCable standalone is run" do
+      before do
+        stub_const('ACTION_CABLE_SERVER', true)
+        stub_config(action_cable: { worker_pool_size: 8 })
+      end
+
+      it_behaves_like "valid runtime", :puma, 11
+    end
   end
 
   context "unicorn" do
     before do
       stub_const('::Unicorn', Module.new)
       stub_const('::Unicorn::HttpServer', Class.new)
+      stub_config(action_cable: { in_app: false })
     end
 
     it_behaves_like "valid runtime", :unicorn, 1
+
+    context "when ActionCable in-app mode is enabled" do
+      before do
+        stub_config(action_cable: { in_app: true, worker_pool_size: 3 })
+      end
+
+      it_behaves_like "valid runtime", :unicorn, 4
+    end
   end
 
   context "sidekiq" do
@@ -105,17 +132,4 @@ describe Gitlab::Runtime do
 
     it_behaves_like "valid runtime", :rails_runner, 1
   end
-
-  context "action_cable" do
-    before do
-      stub_const('ACTION_CABLE_SERVER', true)
-      stub_const('::Puma', Module.new)
-
-      allow(Gitlab::Application).to receive_message_chain(:config, :action_cable, :worker_pool_size).and_return(8)
-    end
-
-    it "reports its maximum concurrency based on ActionCable's worker pool size" do
-      expect(subject.max_threads).to eq(9)
-    end
-  end
 end