[Web-SIG] Web Site Process Bus

[Graham Dumpleton]

On 26/06/07, Ian Bicking <ianb at colorstudy.com> wrote:
> For instance, doesn't atexit work fine for exiting?  (Not in mod_python,
> but I still don't know why it *shouldn't* work in mod_python.)

Exit functions registered by atexit don't work in mod_python for a few reasons.

First off is that if you call Py_Finalize() then Python only calls
exit functions on the main Python interpreter and does not do it on
sub interpreters. Since code running under mod_python tends to run in
sub interpreters, any atexit registered functions would never be
called.

The second problem is that calling Py_Finalize() was disabled in more
recent versions of mod_python as it was causing lots of problems with
strange Python exceptions and sometimes crashes occurring when
triggered.

In mod_wsgi I managed to work out what all the problems were and in
mod_wsgi it will correctly call atexit registered functions registered
in all sub interpreters as well as call Py_Finalize() to clean up
other stuff related to any interpreters which were created. The
changes in mod_wsgi even deal with changes made in Python 2.5 with how
threads are killed off on killing a sub interpreter. Prior to 2.5 this
was managed by an atexit registered function from threading module
itself, but in 2.5 the Python C code itself triggers the cleanup
actions for threads.

Going back and fixing all this in mod_python is right down at the end
of the reopened issue for Py_Finalize() causing problems in the first
place.

  https://issues.apache.org/jira/browse/MODPYTHON-109

All the code in mod_python for Python initialisation and shutdown,
plus interpreter management really needs to be completely rewritten as
it is messy and still has bugs in there related to simplified GIL API,
something which has again been fixed up in mod_wsgi.

Graham