A few users see a blank page

Arne Kepp ak at openplans.org
Sun Feb 10 17:54:40 CET 2008

Pretty much all my pages are in the 10k to 30k range, so I guess I am 
confirming this. It sucks that this is so hard to reproduce :(

I'm considering moving all the stuff I want cached to a different 
hostname / ip address, and let the clients talk directly to Apache again 
for the pages themselves, but that defeats half the purpose.


Marco Molinari wrote:
> 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
> everything.
> 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?
> Thanks
> Marco
>> 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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