A few users see a blank page

Marco Molinari marco.molinari at gmail.com
Thu Feb 7 16:30:53 CET 2008

On Feb 6, 2008 2:57 AM, Arne Kepp <ak at openplans.org> wrote:
> (Maybe this should be on -misc ?)

Ok, moved.

Thank you for your reply. I'm using PHP and I had it gzip'ing, then I
tried to use mod_deflate, but they're reporting the problem anyway.

But I think the problem is similar. In fact, thanks to a user, I did
some tests and I discovered that:
- they can see static content, even html, any length
- they can see content generated by PHP if it's smaller than 7500 bytes
- they get a blank page if PHP output is more than 8000 bytes
- they see everything if the accelerator is Squid

I disabled compression during these tests. Maybe your users see a
blank page just sometimes, when they request a page that, compressed,
is larger than 7500/8000 bytes?

Sorry I don't have a precise number, but I didn't want to stress my
user too much, but I suppose I can work that out.

I can't replicate this myself; I tried to use Squid (even different
versions) on the client side, to replicate their setup, but I just see

My VCL is quite simple, too, lookup for images/css and pipe/pass for
everything else.

Any idea of what's happening? What can I do to find more clues?


> I've seen one odd (to me) problem like this that I was able to reproduce
> consistently, thanks to the help of a user. If you are serving PHP, and
> PHP is gzip'ing the output then clients behind a Squid proxy (on their
> end) only get blank pages.
> Squid records something like "TCP_MISS/200 416 GET <script name>? -
> DIRECT/<ip address> text/html" in the logs, but doesn't appear to get
> the page.
> Moving gzip compression from PHP to Apache solved this particular
> problem, but I still have users reporting blank pages every now and
> then. I've been accused of blocking all sorts of clients for this reason.
> My VCL file is simple, it's the standard logic + lookup for image and
> css extensions and pass for everything else (also tried pipe).
> -Arne
> Marco Molinari wrote:
> > Hi,
> > I recently deployed Varnish and its performance is simply incredible.
> > I'm having a problem, though, which made me jump back to Squid. In the
> > week I used Varnish I had some users mailing me that they couldn't see
> > the site anymore, they just saw a blank page.
> > It seems this affects a small percentage of the users, as I got just
> > about 10 emails in a week and my users are in the 10000s, and in fact
> > I didn't notice any problem in the stats; so I setup two servers, one
> > with Squid and the other with Varnish, and the affected users see the
> > site only through Squid.
> >
> > I'm trying to understand what's happening and with the help of some
> > users here's what I discovered:
> > - every user who has problems connects from an office (completely
> > different places, of course)
> > - at least one user connects via a proxy (she has a header that says
> > "Via: 1.1 SRVFW1")
> > - Apache serves the page, which is logged with the correct size
> > - they can see very small pages (a test I did just printed "Thanks " +
> > the timestamp)
> >
> > This happens both with 1.1.2 and trunk.
> >
> > On standard log files I can't find anything, I couldn't even know it
> > was happening if those users didn't email me. I'd like to have more
> > data before submitting a bug report; do you have any suggestion on how
> > and what I could collect?
> >
> > Thanks
> > Marco Molinari
> > _______________________________________________
> > varnish-dev mailing list
> > varnish-dev at projects.linpro.no
> > http://projects.linpro.no/mailman/listinfo/varnish-dev
> >
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> >
> >

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