How should I deploy a patch to a Passenger-based production Rails application without downtime?

Question

I have a Passenger-based production Rails application which has thousands of users. Occasionally we need to apply a code patch (we use git) and the current process for doing this (you can assume there are no data migrations) is:

• Perform git pull origin [production-branch-name] on the server
• touch tmp/restart.txt to restart Passenger

This allows us to patch the server without having to resort to putting up a maintenance page, which is great, but it doesn't feel quite right since it's not actually a proper 'deployment', and we still need to manually update the revision file and our deployment doesn't appear in the Hoptoad or NewRelic services we use.

Ideally I would run cap production deploy and just let the standard Capistrano deployment script take care of everything, but is this a dangerous thing to do without putting up a maintenance page? This deployment process seems to be fairly safe in that the new revision is deployed to a completely separate folder and only right at the end of the process is a symlink re-created to switch the currently deployed version, but I'm still fairly paranoid about this somehow resulting in a lost or failed request.

Answer 1

No problems here doing cap production deploy. If the deployment fails then the previous release is still good. Nothing will fail as the old release is loaded (cached) in the current Passenger process. The touch tmp/restart.txt will pick up the new release and all is good in the world.