From Katello mailing list:

Been wanting to be able to get a thread dump from Ruby for a while, similar to Java's 'kill -3'

jweiss pointed me at:

http://www.mikeperham.com/2012/06/02/debugging-with-thread-dumps/

which prompted:

https://github.com/Katello/katello/pull/2631

so, now if you have a ruby process in katello that you want to dump a
thread-dump to see what it is doing do a:

1. kill -TTIN <thin PID>

Nice tiny feature.