SIGUSR2 : open an interactive console using rconsole (http://code.google.com/p/rfoo/) and let me log and muck around with live object while the server process keeps running.[NOTE: don't use on production systems, it opens an RPC port that lets anyone control your process remotely!]
from rfoo.utils import rconsole
rconsole.spawn_server()
Combine with watch
$ watch pstack PID
On RHEL6 pstack is in gdb RPM package.
(bonus: shows all threads)