Merge pull request #28493 from jmgarnier/backport-fix-to-remove-dupli…

…cate-logging-output-from-rails-server

Backport fix duplicate rails server logging output in Rails 4-2-stable

railties/lib/rails/commands/server.rb

@@ -138,11 +138,13 @@ def create_tmp_directories
       def log_to_stdout
         wrapped_app # touch the app so the logger is set up
 
-        console = ActiveSupport::Logger.new($stdout)
+        console = ActiveSupport::Logger.new(STDOUT)
         console.formatter = Rails.logger.formatter
         console.level = Rails.logger.level
 
-        Rails.logger.extend(ActiveSupport::Logger.broadcast(console))
+        unless ActiveSupport::Logger.logger_outputs_to?(Rails.logger, STDOUT)
+          Rails.logger.extend(ActiveSupport::Logger.broadcast(console))
+        end
       end
   end
 end