[Zope] Hanging Python Threads

[Ryan T. Bard]

I have a problem where I periodically get a python thread that never
dies by itself, or dies only after 8+ hours. I have tried to
mitigate the problem by limiting memory and CPU usage of any
individual python thread on my Linux box; it works to a point. A
very small point ;) It does prevent these hangs from completely
stopping site use, but it also prevents the site running as fast as
it could at other times.

I am pretty sure that one of two products is the culprit here:
ZMySQLDA-2.0.8 (latest stable release)
ExtFile-1.1.3 (ExtFile 1.2.0 has since been released with some
issues reported on this list)

The server experiencing the problem is running Redhat Linux 7.2,
Zope 2.5.1, and Python 2.1.3.

I have some very large files which are stored as ExtFile objects
that my users download via HTTP access at the moment (some 100+ MB).
Also, 90% of my website content is dynamically derived from the
MySQL database. There are roughly 1000 users that use the site
consistently throughout each day.

I had found a post (or an archive on the zope.org site) a few weeks
ago about a way to debug python threads or to watch a live traceback
of threads through some debugging method in order to debug products,
but I can't find it again now. I am probably using the wrong search
terms this time around. Anyhow, hoping someone knows a way to trace
the problem back to the product responsible for the thread hangs
(assuming it isn't a problem with either the version of Zope or the
version of Python that I am using).

Thanks for any help,
Ryan