Apache and Dynamic Loading Modules Problems.

Patrick Powell papowell at astart.com
Fri Jun 3 16:27:47 UTC 2016

This is a bit complicated.  I have filed a bug report:

Bug 209585 - www/apache24 dynamic loading of MySQL client library 
generates errors with mod_perl CGI

I suspect that the problem I am seeing is the symptom of something more 

I want to do some further investigation but I have run into a couple of 
roadblocks.   Before I reinvent the round rolling thing I thought I 
would ask the experts for some advice.

It appears (from my limited tests) that the problem happens when Apache 
loads a module which
has duplicate references to the same set of modules.   In this case it 
appears to be the MySQL library.
 From my limited reading,  on FreeBSD Apache uses the dynamic loadable 
library facilities.
Note that this problem does not occur on FreeBSD 9.3 but it does occur 
on 10.X.  This indicates
that there is some change in the support for this between 9.3 and 10.X.  
(But I could be wrong. Just guessing here.)

Just to confuse the issue here,  the two Apache modules which appear to 
cause the problem are
mod_perl + Perl DBD + Mysql support
mod_dbd + APR1 + Mysql via /usr/local/lib/apr-util-1/apr_dbd_mysql-1.so

Can somebody point me to some UP TO DATE or definitive documentation on 
the dynamic loading facility?  There is lots of references to loadable 
kernel modules but not much on how Apache uses dynamic loading.

Secondly,  can somebody suggest a way to try to try to see what is 
happening as Apache loads these modules?  I was thinking about seeing 
what the difference is between loading only one module (no problem) and 
loading two modules (problem) and trying to track down the issue.

Patrick Powell                 Astart Technologies
papowell at astart.com            1530 Jamacha Rd, Suite X
Network and System             San Diego, CA 92019
   Consulting                   858-874-6543 FAX 858-751-2435
Web: www.astart.com

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