call clear_active_connections! in :after_dispatch to give pooled connections back

This fixes connection pool exhaustion for web servers which create new thread per connection (e.g. Webrick).

integration.rb changes are required to keep test transaction active for several requests.
Signed-off-by: NMichael Koziarski <michael@koziarski.com>
[#1171 state:committed]

actionpack/lib/action_controller/dispatcher.rb

@@ -20,6 +20,7 @@ def define_dispatcher_callbacks(cache_classes)
         end
 
         if defined?(ActiveRecord)
+          after_dispatch :checkin_connections
           before_dispatch { ActiveRecord::Base.verify_active_connections! }
           to_prepare(:activerecord_instantiate_observers) { ActiveRecord::Base.instantiate_observers }
         end
@@ -145,6 +146,21 @@ def flush_logger
       Base.logger.flush
     end
 
+    def mark_as_test_request!
+      @test_request = true
+      self
+    end
+
+    def test_request?
+      @test_request
+    end
+
+    def checkin_connections
+      # Don't return connection (and peform implicit rollback) if this request is a part of integration test
+      return if test_request?
+      ActiveRecord::Base.clear_active_connections!
+    end
+
     protected
       def handle_request
         @controller = Routing::Routes.recognize(@request)

actionpack/lib/action_controller/integration.rb

@@ -276,7 +276,7 @@ def process(method, path, parameters = nil, headers = nil)
           ActionController::Base.clear_last_instantiation!
 
           env['rack.input'] = data.is_a?(IO) ? data : StringIO.new(data || '')
-          @status, @headers, result_body = ActionController::Dispatcher.new.call(env)
+          @status, @headers, result_body = ActionController::Dispatcher.new.mark_as_test_request!.call(env)
           @request_count += 1
 
           @controller = ActionController::Base.last_instantiation