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From: "Bert Huijben" <bert@qqmail.nl>
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In-Reply-To: <40F35186-1FFF-48EF-BB67-DAE432526244@greenbytes.de>
Subject: RE: No H2 Window updates!
Date: Sun, 29 Nov 2015 14:48:46 +0100
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> -----Original Message-----
> From: Stefan Eissing [mailto:stefan.eissing@greenbytes.de]
> Sent: zondag 29 november 2015 09:04
> To: dev@httpd.apache.org
> Subject: Re: No H2 Window updates!
> 
> Ok, thanks. I think I have an idea of what's happening:
> - on short request bodies, window updates get omitted and gives a
shrinking
> connection window

Yes, this is the problem I'm seeing. 
I would like to see this fixed for 2.4.18... and I wouldn't be surprised if
this also fixes Jan Erhardts problem.

Web frameworks are likely to issue many small (<16K) posts to a server,
which all fit in a single frame. In my testcase I needed > 500 requests
though.

> - the window size of the connection itself should be at max Value right
from
> the start

That is one solution.  (Google sends one huge window update on the
connection directly at the start, after the settings frame)
But this really needs a proper design behind it...

Optimal windowing is a hard topic. The window needs to be large enough not
to slow down the client... but not too big to hog the server (and by that
the connection), etc. etc.

The problem with a huge connection window up front is that it may be used
for a lot of small requests.... or one large. That large one can easily be
throttled at the stream level, while those small ones can't.
> 
> I won't be able to do anything about it until later this week, though.


With an increased default window on the httpd site the Subversion test now
completes successfully over H2 on 2.4.17 and 2.4.18.
It just reports an XPASS in a specific case where we assume that httpd
handles a request as invalid because one header is to long with the http/1.1
rules.

If this change is expected on the httpd site, the assumption should be fixed
in the Subversion testsuite.

Thanks,

	Bert