Just add connection management middleware if running in a concurrent environment.

3 files changed, 19 insertions, 7 deletions

diff --git a/activerecord/lib/active_record/railtie.rb b/activerecord/lib/active_record/railtie.rb
index 2808e199fe..eff51a7c87 100644
--- a/activerecord/lib/active_record/railtie.rb
+++ b/activerecord/lib/active_record/railtie.rb
@@ -16,11 +16,7 @@ module ActiveRecord
     config.generators.orm :active_record, :migration => true,
                                           :timestamps => true
 
-    config.app_middleware.insert_after "::ActionDispatch::Callbacks",
-      "ActiveRecord::QueryCache"
-
-    config.app_middleware.insert_after "::ActionDispatch::Callbacks",
-      "ActiveRecord::ConnectionAdapters::ConnectionManagement"
+    config.app_middleware.insert_after "::ActionDispatch::Callbacks", "ActiveRecord::QueryCache"
 
     rake_tasks do
       load "active_record/railties/databases.rake"
@@ -72,6 +68,13 @@ module ActiveRecord
       end
     end
 
+    initializer "active_record.add_concurrency_middleware" do |app|
+      if app.config.allow_concurrency
+        app.config.middleware.insert_after "::ActionDispatch::Callbacks",
+          "ActiveRecord::ConnectionAdapters::ConnectionManagement"
+      end
+    end
+
     config.after_initialize do
       ActiveSupport.on_load(:active_record) do
         instantiate_observers
diff --git a/railties/test/application/initializers/frameworks_test.rb b/railties/test/application/initializers/frameworks_test.rb
index 4ff10091b1..d8e916f45f 100644
--- a/railties/test/application/initializers/frameworks_test.rb
+++ b/railties/test/application/initializers/frameworks_test.rb
@@ -98,7 +98,17 @@ module ApplicationTests
 
       require "#{app_path}/config/environment"
 
-      expects = [ActiveRecord::ConnectionAdapters::ConnectionManagement, ActiveRecord::QueryCache, ActiveRecord::SessionStore]
+      expects = [ActiveRecord::QueryCache, ActiveRecord::SessionStore]
+      middleware = Rails.application.config.middleware.map { |m| m.klass }
+      assert_equal expects, middleware & expects
+    end
+
+    test "database middleware initializes when allow concurrency is true" do
+      add_to_config "config.threadsafe!"
+
+      require "#{app_path}/config/environment"
+
+      expects = [ActiveRecord::ConnectionAdapters::ConnectionManagement, ActiveRecord::QueryCache]
       middleware = Rails.application.config.middleware.map { |m| m.klass }
       assert_equal expects, middleware & expects
     end
diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index e66e81ea2c..ed06b4c767 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -28,7 +28,6 @@ module ApplicationTests
         "ActionDispatch::RemoteIp",
         "Rack::Sendfile",
         "ActionDispatch::Callbacks",
-        "ActiveRecord::ConnectionAdapters::ConnectionManagement",
         "ActiveRecord::QueryCache",
         "ActionDispatch::Cookies",
         "ActionDispatch::Session::CookieStore",