[PATCH] A modular mod_log_config for Apache 2

[Sönke Tesch <st...@bitbrook.de>]

Hi,

I wasn't too happy with the current mod_log_config design, which turned
out to be a bit unflexible in the writer section, so I modified it in 
order to be able to happily log into a database. The disadvantages of
the existing set_writer way of doing things are:

a) The log writer doesn't get all the details of the items to log (namely
if they exist or not, i.e. is it 0,"-","NULL" or NULL?), you have to stick
with whatever string mod_log_config assembles.

b) First everything gets converted into a string only to be converted
back to bits and bytes by the database (e.g. MySQL will accept raw data
in upcoming releases). Guess this might be a waste of cycles, even if 
compared to my new design ;)

c) You cannot use several log writers at the same time (e.g. log one host
into a file and another one into a database). Or at least you'll have
to add a bunch of new configuration commands.


My approach is simply to move the data -> string conversion from the various
log item functions to the log writer itself (and there possibly to decide to
dump it completely).
Instead of returning strings the log item functions fill out a data block 
with a pointer to the data (or NULL if the item does not exist) and a type
identifier (basically number, string, datetime). The log writer then does
whatever it thinks is correct with this data chain.

Log writer selection is done within the configuration files by giving
Custom-/TransferLog a URL-like descriptor. For example, to log into 
"log/virtual_only" using the file writer, 

  TransferLog file:log/virtual_only

can be used. This is easily extendable, MySQL can e.g. be accessed using

  CustomLog   mysql:user@host/database "insert ..."

Of course, LogFormat is usable, too. So, whatever writer you use, the
important stuff can stick to the place where it has always been.

Build-in are a file:- (default) and a pipe:-writer. Other writers can be
added using a function, this works almost like the old set_writer calls.
See mod_log_mysql for an example.


The whole thing is 100% backwards compatible (which might make the code
look a bit messy :). 
mod_log_config still accepts data from old-style external log item functions
as well as old-style file/pipe paths in Custom-/TransferLog. The set_writer-
functions still work, too.


That said, I'm a bit unsure if the implementation is correct and bug-free,
although it seems to work on my own server - after all, I'm new to this.
I'd be happy about any helpful comments on design issues and other thoughts
and suggestions.


I don't know if it's ok to post the hole 60k here (diff or c doesn't matter),
so I put everything up at http://bitbrook.de/privat/st/mod_log_mysql/ , 
hope nobody minds.


Thanks,
  soenk.e