Awhile back I upgraded the “rack” gem on one of our CentOS Linux servers that runs LiteSpeed and Ruby. The upgrade took the rack gem from rack version 1.0.0 to rack version 1.0.1. After upgrading the Rack gem I attempted to visit the site located on the server where the gem was updated only to receive a 503 error from LiteSpeed. During the troubleshooting process I looked at the LiteSpeed error logs and noticed errors that lead me back to the Rack gem I had just updated. Below I describe the error in more detail and what can be done to resolve the issue of rack-1.0.1.