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From Jens Schleusener <>
Subject Re: [users@httpd] 2.3.15-beta: module proxy_balancer requires the not automatically loaded module slotmem_shm
Date Thu, 10 Nov 2011 17:19:49 GMT
On Thu, 10 Nov 2011, Rainer Jung wrote:

> On 09.11.2011 21:20, William A. Rowe Jr. wrote:
>> On 11/9/2011 4:53 PM, Jim Jagielski wrote:
>>> Isn't the point different? If someone enables mod_proxy then the
>>> configure script needs to ensure that mod_slotmem is also built…
>> Reporter suggests that *NOT* loading mod_slotmem_shm caused the server
>> to start correctly; exactly the inverse of what we would expect.
> No, his subject is "module proxy_balancer requires the not automatically
> loaded module slotmem_shm" ("the not" and not "to not") and he writes
> "Ok, so I simply removed in the installed default httpd.conf the comment
> sign within the line
>  #LoadModule slotmem_shm_module modules/
> and as expected now all works. "

I am the OP and yes, Rainer interprets me correctly.

And here a small addition:

Just for curiosity I added "dav_lock" to my previosly used configure 
options (don't ask why, just "historical" reasons):

  ./configure --prefix=/usr/local/www/httpd2.3.15-beta_with_dl \
  --enable-so --disable-ldap --with-included-apr --with-pcre=/usr/local/soft \
  --enable-mods-shared="most cache mem-cache dav_lock mime-magic proxy ssl unique_id"

Some relevant entries from the so generated default httpd.conf:

  #LoadModule slotmem_shm_module modules/
  #LoadModule dav_module modules/
  #LoadModule dav_fs_module modules/
  LoadModule dav_lock_module modules/

If I now issue "bin/apachectl start" I got the error

  httpd: Syntax error on line 138 of
  /usr/local/www/httpd2.3.15-beta_with_dl/conf/httpd.conf: Cannot load
  /usr/local/www/httpd2.3.15-beta_with_dl/modules/ into server:
  undefined symbol: dav_push_error

Remark: This error was output to the console and not as yesterday "only" 
to the error_log so I detected yesterday the problem only later since the 
httpd wasn't running (probably since the errors have different qualities 
and/or occur at different phases).

Ok, in this case I had not only to activate/load the "slotmem_shm_module" 
but also to remove the comment sign from the following httpd.conf line

  #LoadModule dav_module modules/

to let apache load the required "dav_module". Probably a very similar 
configuration dependency problem.

> I think at the moment there is some tendency to further reduce the
> default active LoadModules to a very small module set (see elsethread)
> and not activate the other enabled modules. Module set at build time is
> only loosely coupled to needed modules at run time.
> Jim's suggestion still makes sense: even if we do not activate most
> modules by default, some modules have dependencies to other modules and
> when a module with such a dependency is build (enabled), we could build
> the dependencies automatically as well. Modules with dependencies are at
> least mod_ssl (for the session cache), mod_proxy_balancer, and I think
> the heartbeat stuff. Probably also ldap auth needing mod_ldap.
> On the other hand we now build "most" by default and there are "all" and
> "reallyall", *and* we now only activate few modules by default. So most
> users should not have a real need to add individual modules to the list
> of modules to build.
> IMHO the automatic dependency handling in configure is not a must. We
> could add after GA if users really need it.
> Regards,
> Rainer



P.S.: OT ("information" respectively "promotion"): By the way I use the 
apache httpd server for "my" FOSS software archive and naturally the 
according tarballs are there also available, for e.g. under

or under the more general and version independent start URL

Why I write this (with bad conscience)?

That site allows source code browsing, downloads with different 
compression formats, generates a CLOC statistic (ok, a gimmick), for e.g.

and offers Doxygen-generated source code documentation (ok, for httpd the 
dependency graphs are sometimes a little bit gigantic and confusing),
for e.g.

in the hope that it helps the developers of the FOSS community.

But probably apache teams have its own more specific according tools ;-)

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