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Date: Tue, 08 Jan 2002 23:09:06 +0200
From: Eli Marmor <marmor@netmask.it>
Organization: Netmask (El-Mar) Internet Technologies
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To: dev@httpd.apache.org
Subject: Re: API for runtime httpd  config ?
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ilker ARABACI wrote:

> Is there any API used or on progress to get httpd global and configuration
> values on runtime,
> (not an httpd.conf file parser), something and more detailed like info
> module does,
> And also it would be more helpful to manuplate what will httpd  act as
> without restarting nor reloading,
> to keep the active (unrelated to changes)  sessions and connections up.

Your questions raised a serious drawback of Apache: on-the-fly
administration/configuration. In my humble opinion, it's even the main
drawback of Apache (and the only thing that stands between Apache and
perfection).

Historically, any module parses its directives. There are some public
functions, but they are too basic, and each module decides what is
valid and what is not, how to translate each string, and even where to
store it. Some directives even use a "raw" parsing - i.e. no rules
regarding how many flags the directive should have. Modules may even
ignore directives.

Asking Apache to re-read its configuration is problematic too; Even the
primitive way, of "killing" it, is impossible, because a non-root user
can't kill a root user, even if it is its parent. Also, there is no
mechanism for transferring messages from the children to the parent
initiated by the children, but only vice versa (e.g. scoreboard). There
are some "creative" alternatives, like exiting with codes that the
parent will "understand" as requests to do specific things (like stop/
restart/graceful), but this method is too tricky, doesn't work in 100%
of the cases and the platforms, limited (you can't pass more details),
and has a lot of other problems.

These problems makes the mission of developing a GUI for Apache almost
impossible, and the results - although should be admired considering
the tight constraints - are very disappointing.

Some solutions for both problems were discussed in the past. A *MAJOR*
change in the format of httpd.conf and its handling could help. For
example, migrating to XML, and replacing the conf structures by
structures with offsets to the member in another structure where the
module stores its attributes, plus functions for validation/conversion
/reverse-conversion for each "type", could resolve almost everything.
It helped X (although the syntax was a little different - not XML),
and there is no reason why Apache should differ. Of course, adding a
pre-processor which will convert XML syntax to the current syntax,
doesn't solve anything...

"Unfortunately", Apache is the most popular web server, and millions
sites are already powered by it. It means that millions configuration
files will not be compatible with the new syntax. In addition, there
are hundreds of modules, and all of them will not be compatible with
the new syntax and C structures, unless ported to them.

This is why the "revolution" will never happen, so your questions will
remain unanswerred forever.

Note: We are trying to add functions to meet your second need -
apr_stop(), apr_restart(), apr_graceful(). When one of these functions
is called by the parent, it will stop/restart/graceful itself. When it
is called by a child, it will inform the parent in a special "pipe"
that will be listened by the parent. Once the parent receives anything
in this pipe, it will decode it, and call anything needed.

If it works perfectly with all the MPMs, we will probably contribute
it.
-- 
Eli Marmor
marmor@netmask.it
CTO, Founder
Netmask (El-Mar) Internet Technologies Ltd.
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