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Re: immense Apache memory leak, plus patch

From: Mark Phippard <markphip_at_gmail.com>
Date: Tue, 8 Sep 2009 12:13:11 -0400

On Thu, Sep 3, 2009 at 10:14 AM, Mark Phippard<markphip_at_gmail.com> wrote:
> On Thu, Sep 3, 2009 at 9:45 AM, C. Michael Pilato<cmpilato_at_collab.net> wrote:
>> Blaise Tarr wrote:
>>> Greg Stein wrote:
>>>> I don't see how this would work, however, because there are *still* a
>>>> lot of uses of the 'output' variable. Just changing the one in
>>>> ap_pass_brigade() is going to be insufficient. Seems that all of them
>>>> should really be changed.
>>> That patch is just the bare minimum to prevent the crashes we've
>>> experienced, and it confirms the source of the problem, but it's
>>> definitely not the proper fix. Sorry, I should have stated that earlier.
>>> It works because the pointers in the 'output' ap_filter_t struct still
>>> happen to be valid, or so it seems.
>>> Changing all the references to 'output' would more correct, but that
>>> would essentially render the 'output' function parameter useless, and
>>> that doesn't feel right.
>>> One possibility is to create a dummy (sentinel) filter at the beginning
>>> of the filter chain that would simply pass the brigade along. It would
>>> always be present, and references to the filter chain using it would
>>> always be valid. Implementing it would be more appropriate in Apache
>>> itself, but there should be no harm in having mod_dav_svn do it.
>> Please excuse my ignorance, but what would such a filter look like?
>> Anything like the following?
>> apr_status_t
>> dav_svn__dummy_filter(ap_filter_t *f,
>>                      apr_bucket_brigade *bb)
>> {
>>   return ap_pass_brigade(f->r->output_filters, bb);
>> }
> Mike,
> Did you see this?
> http://httpd.apache.org/docs/trunk/developer/output-filters.html
> How would we guarantee this would be put at the beginning of the
> filter chain?  Is that possible?
> Is it possible to detect that mod_deflate has removed itself from the
> chain and not call it?

Anyone have any comments on these questions?

Has anyone looked into whether mod_deflate could be patched? Maybe it
could just pass along the brigade rather than removing itself from the
filter chain?

Mark Phippard
Received on 2009-09-08 18:13:32 CEST

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