call (ActiveRecord::ConnectionAdapters::ConnectionManagement)

    # File lib/active_record/connection_adapters/abstract/connection_pool.rb, line 360
          def call(env)
            @app.call(env)
          ensure
            # Don't return connection (and peform implicit rollback) if
            # this request is a part of integration test
            unless env.key?("rack.test")
              ActiveRecord::Base.clear_active_connections!
            end
          end