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Re: [Xen-devel] Problem with apache proxying between domains

Andrew Athan wrote:

The attached network sniff header lines from Ethereal show the
communication between (browser) and
(dom0) which proxies to (dom1).  You will see that we go
to a ZeroWindow condition with about 3 Megs transferred out of the dom0
proxy.  At the tail end -- the TCP connection is then kept alive, but
the QuickTime plugin never becomes "enabled" and can't play the movie.

Can you attach to the process via strace or something and check
what it's doing? Is it getting scheduled or waiting on IO?
Since it keepalives successfully, I'm assuming your interface
hasn't gone down. Also, check for a memory failure - could be
a mem leak.

Fetching the same URL via CURL on the Windows host, dom0 host, or a
separate physical linux host works fine.  I also created a separate
Apache instance on a physically separate linux host, with the exact same
Rewrite rules.  Fetching the movie through this proxy works fine in both
the QuickTime plugin AND CURL.  I did this to eliminate the possibility
of some basic incompatibility between mod_proxy/mod_rewrite and
quicktime movies fetched by the quicktime browser plugin.

It does look like reading process stops reading. Did you
alter the default socket buffer sizes, at all, btw?

I have played with the ProxyIOBufferSize and ProxyBufferSize parameters
in the apache isntance in dom0, and have also tried various combinations
of bvt weights, warpback, etc.

Should I try to capture a sniff of xen-br0 during this interchage?  Will
that help?  WHen I tried this I think I only got partial data, perhaps
because of the xen domain scheduling causing missed packets.

You do seem to be missing packets in your trace as well.

netstat -tan
netstat -s
ifconfig -a

would be useful on both dom0 and of course, dom1..


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