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From: Stefan Fritsch <sf@sfritsch.de>
To: dev@httpd.apache.org
Subject: Re: svn commit: r821477 - in /httpd/httpd/trunk: CHANGES
 modules/http/byterange_filter.c modules/http/http_filters.c
 server/core_filters.c
Date: Sun, 4 Oct 2009 10:54:11 +0200
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On Sunday 04 October 2009, Paul Querna wrote:
> > URL: http://svn.apache.org/viewvc?rev=821477&view=rev
> > Log:
> > Make sure to not destroy bucket brigades that have been created
> > by earlier filters. Otherwise the pool cleanups would be removed
> > causing potential memory leaks later on.
> 
> I am not sure these changes make sense.  The 'traditional' API view
> says that brigades passed down the output fitler chain should be
> destroyed, not cleared -- please see the thread started with this
> message:
> <http://mail-archives.apache.org/mod_mbox/httpd-dev/200504.mbox/%3C
> 9ccfb16df2220fc31c836bb7cd640554@ricilake.net%3E>
> 

This is at odds with the documentation at 
http://httpd.apache.org/docs/trunk/developer/output-filters.html , in 
particular with rules 6 and 9 at the end. If output filters reuse 
brigades, the core must not destroy them.

I just noticed that include/util_filter.h still says "The caller 
relinquishes ownership of the brigade" for ap_pass_brigade(). Either 
output-filters.html or util_filter.h must be changed.

In my opinion, it is much better to not destroy the brigades and reuse 
them instead of creating a new brigade on every filter invocation. 
Otherwise there is huge memory usage for streaming content.

The thread you have pointed out also has a suggested patch for the 
docs in util_filter.h:

http://mail-archives.apache.org/mod_mbox/httpd-
dev/200504.mbox/<20050426102834.GE16976@redhat.com>

It is not clear from the thread why it wasn't applied.