[mod_python] Threading and apache.import_module

michael bayer mike_mp at zzzcomputing.com
Sun Jun 19 22:14:21 EDT 2005

On Jun 19, 2005, at 6:34 PM, Graham Dumpleton wrote:

> I would advise against trying to accomodate ".pyc" files. If you  
> were to
> do this you will in practice have to monitor the timestamps on both  
> the
> ".py" and ".pyc" files and contend with issues such as what to do when
> the ".pyc" file is removed but the ".py" still exists but you were  
> originally
> loaded from the ".pyc" file. Similarly, what do you do if you are  
> loaded
> from the ".pyc" file and the ".py" file is removed. Does this imply  
> that
> the user is intending the page to now no longer be available. Another
> cases is what do you do if you are loaded from the ".pyc" file and the
> ".py" file modification time is changed to be older than what it  
> was before.
> Do you take this as meaning that an older file has been restored and
> that should be used instead. As you can see you have to make various
> assumptions and in some respects hope for the best. Although it can
> be made to work in a reasonably sensible way, I found it complicates
> the code unnecessarily and not worth the trouble, especially when
> Apache generally runs as a user where ".pyc" files can't be created in
> the first place.

ah well, I can definitely make assumptions as I'm talking  
specifically about modules loaded for Myghty, and the primary ".py"  
modules I am loading were generated from template files, so its  
already a given that there is a "data directory" configured where the  
Apache process can write .py files, and theres no problem assuming  
that a .py file must exist for each .pyc file else it gets recreated  
by the template, and they arent really part of a "package".    For a  
large set of several hundred or thousands of templates, which are  
released from memory on a least-recently-used scheme, a lot of them  
will be falling out of memory and getting re-loaded back in again  
repeatedly;  the .pyc factor has a sizeable impact on how much work  
the server has to do, particularly upon startup or creation of new  
child processes, and also within setups that are sensitive to  

I also have support for plain .py modules with callable functions/ 
objects in the spirit of Vampire/Publisher, but similarly they are  
just the end-points to handling a request...they arent really meant  
to be imported by other modules and I only seek to support basic  
reloading functionality for them;  if you change the back-end to code  
you would still have to restart the server.  Generally I would base  
module loading/reloading upon the existence/timestamp of the .py  
file, and then look for the .pyc file existence/timestamp as a second  
step, the way imp.load_source does (which is what Im using now).

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