filter priorities and order of execution

Hi,

I'm still looking at getting range requests working properly with
mod_perl:

    http://www.gossamer-threads.com/lists/modperl/dev/104360

and have decided to go with an output filter to set the eos bucket. 

Can anyone help with how order execution works? I have a simple conf
like:

    PerlRequire /home/alex/modperl.pl
    <Location /perl/>
        SetHandler modperl
        PerlResponseHandler VideoTest
        PerlOutputFilterHandler VideoTest::test_output_handler
    </Location>

and my modperl code looks like:

    sub handler {
        my $r = shift;
        $r->sendfile('/tmp/video.mp4');
        $r->pnotes("send_eos" => 1);
        $r->add_output_filter(\&test_add_output_filter);
        return Apache2::Const::OK;
    }

    sub test_add_output_filter {
        # transparent filter
        my ($f, $bb) = @_;
        warn "in add_output_filter";
        my $rv = $f->next->pass_brigade($bb);
        return $rv unless $rv == APR::Const::SUCCESS;
        warn "leaving add_output_filter";
        return Apache2::Const::OK;
    }

    sub test_output_handler {
        # sets eos depending pnotes
        my ($f, $bb) = @_;
        warn "in test_output_handler";
        my $r = $f->r;
        if ($r->pnotes("send_eos")) {
            warn "adding eos";
            my $ba = $bb->bucket_alloc;
            my $b = APR::Bucket::eos_create($ba);
            $bb->insert_tail($b);
        }
        else {
            warn "skipping eos modifications";
        }
        my $rv = $f->next->pass_brigade($bb);
        return $rv unless $rv == APR::Const::SUCCESS;

        warn "leaving test_output_handler";

        return Apache2::Const::OK;
    }

and the debug looks like:

    in test_output_handler at /home/alex/modperl.pl line 31.
    skipping eos modifications at /home/alex/modperl.pl line 40.
    [Tue May 29 09:05:20 2012] [debug] byterange_filter.c(256): [client 127.0.0.1] found unknown length: clength = 125569
    leaving test_output_handler at /home/alex/modperl.pl line 46.
    in test_output_handler at /home/alex/modperl.pl line 31.
    adding eos at /home/alex/modperl.pl line 34.
    in add_output_filter at /home/alex/modperl.pl line 21.
    leaving add_output_filter at /home/alex/modperl.pl line 24.
    leaving test_output_handler at /home/alex/modperl.pl line 46.

I know I have add_output_filter and perloutputfilterhandler, just trying
to see which option runs when (as ideally add_output_filter would work
best). 

So my questions are:

1. Why does test_output_handler set by PerlOutputFilterHandler get
called twice?

2. Why does the first time called not know about pnotes, but the second
time it does?

3. Why does add_output_filter happen at the end, and is there a way to
have it happen at same position as perloutputfilterhandler?

Basically, in order for range requests to work, I need to set the eos
bucket before byterange_filter is called. If it happens after that, it's
too late and range requests won't work.

Any help is really appreciated, been struggling here for quite some time.
=)

Thanks!

Alex