Defining mandatory parameters for Apache modules

[Raj Iyer <Ra...@openwave.com>]

 

Hello, 

 

The Apache web server on start up iterates through the list of
configuration directives and invokes the associated module handler for
each directive. 

 

For e.g. if module A has handlers for directives D1 and D2, then the
httpd process on start up will invoke the handlers within module A when
it encounters D1 and D2 in httpd.conf.

 

However, what is the best way to find out missing mandatory parameters
from within the module. For e.g. if a directive D3 is mandatory for the
module to work, then how can the module on initialization guarantee that
this configuration parameter is provided? 

 

I do not want to provide a default value for this mandatory
configuration directive and also, I do not want to check whether this
mandatory directive is defined or not while handling each request. 

 

Thanks in advance,

Best regards,

Raj Iyer

 

RE: Defining mandatory parameters for Apache modules

["Houser, Rick" <Ho...@aoins.com>]

There's a hook for processing your configuration and making any changes
(offhand, post-config?).  If any of this is done on a file or directory
level, you can do that in your configuration merge callbacks.  I have to
do something similar where a forwarding capability might be enabled, but
the location to forward is still null, etc.


Thanks,

Rick Houser
Auto-Owners Insurance
Systems Support
(517)703-2580
 

> -----Original Message-----
> From: Ray Morris [mailto:support@bettercgi.com] 
> Sent: Thursday, August 13, 2009 10:13 AM
> To: modules-dev@httpd.apache.org
> Subject: Re: Defining mandatory parameters for Apache modules
> 
>    This may be a level problem.  Are you thinking of throwing 
> an error if it's unset, or simply disabling the module for that 
> VirtualHost, directory, etc.?  Pretty much any module must do 
> a check with each request to see if it should handle the request - 
> for example the module may be wanted in one virtual host and 
> ot another, so you typically have an "enable" directive like 
> RewriteEngine On.  At configuration time, if you don't have 
> your required directive you don't enable your module.  That's 
> how most standard modules work, it seems.  For example if you
> don't use AuthUserFile you simply don't authenticate against 
> any file.  You say you don't want to check with each request, 
> but you already have to check whether or not your enabled with
> each request, for most any module.  Of course, if this required
> directive is the only required directive, you can use it as 
> your "enabling" directive, without needing any "MeEnabled"
> directive.
> 
>    However, I have a feeling, based on little but intuition, 
> that you can solve your actual problem by looking it from one 
> level higher or lower.  Not knowing what your module is supposed
> to do or what the directive is, I can't give any example of 
> looking at the problem from a higher level.  At a lower level, 
> ask "how can I make a missing or default value work?".  You've
> said you don't want to do that, but think about it again.  At 
> the higher level, back up to whatever the module is supposed 
> to accomplish - the business goal.  How can that goal be 
> accomplished in a different manner that doesn' need the 
> directive?  (IE, instead of asking "how can I buy a car to 
> get to work when I haven't gotten paid yet?", ask "how can I 
> get to work without having a car?").
> --
> Ray Morris
> support@bettercgi.com
> 
> Strongbox - The next generation in site security:
> http://www.bettercgi.com/strongbox/
> 
> Throttlebox - Intelligent Bandwidth Control
> http://www.bettercgi.com/throttlebox/
> 
> Strongbox / Throttlebox affiliate program:
> http://www.bettercgi.com/affiliates/user/register.php
> 
> 
> On 08/13/2009 08:34:42 AM, Raj Iyer wrote:
> >  
> > 
> > Hello, 
> > 
> >  
> > 
> > The Apache web server on start up iterates through the list of
> > configuration directives and invokes the associated module handler 
> > for
> > each directive. 
> > 
> >  
> > 
> > For e.g. if module A has handlers for directives D1 and D2, then the
> > httpd process on start up will invoke the handlers within module A
> > when
> > it encounters D1 and D2 in httpd.conf.
> > 
> >  
> > 
> > However, what is the best way to find out missing mandatory 
> > parameters
> > from within the module. For e.g. if a directive D3 is mandatory for
> > the
> > module to work, then how can the module on initialization guarantee
> > that
> > this configuration parameter is provided? 
> > 
> >  
> > 
> > I do not want to provide a default value for this mandatory
> > configuration directive and also, I do not want to check 
> whether this
> > mandatory directive is defined or not while handling each request. 
> > 
> >  
> > 
> > Thanks in advance,
> > 
> > Best regards,
> > 
> > Raj Iyer
> > 
> >  
> > 
> > 
> 
> 
> 
>