New importer redundantly reloading modules.
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Key: MODPYTHON-219
URL: https://issues.apache.org/jira/browse/MODPYTHON-219
Project: mod_python
Issue Type: Bug
Components: importer
Affects Versions: 3.3.1
Reporter: Graham Dumpleton
Fix For: 3.3.x


Although the new module importer prevents two threads trying to load a modul
e at the same time, the transition from checking to see if a module requires
 (re)loading to the actual loading isn't properly thread protected and as a 
result a second thread, alt
hough it may decide a module needs (re)loading, isn't simply waiting for the
 first thread to finish the loading and use the result of that and is instea
d loading the module again even though no change has been made.

This issue was highlighted in following mailing list posts:

http://www.modpython.org/pipermail/...May/023583.html
http://www.modpython.org/pipermail/...May/023586.html

Further discussion can be found in the associated posts for that thread in t
he archives.

Note that this only affects multithreaded Apache MPMs and the window for thi
s to happen is very small and is only going to occur under heavy load from m
ultiple clients or in web pages where multiple requests may be made from a p
age to a resource requiring
the same code module be loaded.

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