Is it possible to update a route,model or controller.js file without restarting the Node.js Server?.

I'm currently dealing with a client who wants constant changes to the application in a very frequent event. And the application deals with user session etc.. Whenever we make any changes to the application it requires a restart for the update to get reflect, which is very expensive in-terms of an high traffic situation.

I have seen some server application providing a feature called [Rolling Restart](https://www.phusionpassenger.com/enterprise) but again I'm not sure whether it is a good way to maintain the user session across the restart event. Or do we have any other solution to deal with this kind of situation.