Re: [squid-users] Duplicate If-None-Match headers

On Mon, Apr 30, 2012 at 11:32 PM, Andy Taylor <andy_at_tayble.com> wrote:
> Hi,
>
> I'm having a number of problems with Squid at the moment with duplicate
> Etags in the headers. I'm using Squid as an accelerator to forward traffic
> to Apache, which serves up a Drupal installation.
>
> After roughly 3 days, a number of pages on the site start to fail with 400
> Bad Request errors; it starts with just a few and then slowly spreads to
> more pages. I did a tcpdump of the requests coming from Squid to Apache, and
> Apache is spitting out a 400 error because of the header size. Hundreds of
> etags are appearing in the If-None-Match headers field, which hits Apache's
> header size limit, causing the error. The only way I've found to 'fix' this
> so far is to either:

So, this is probably poor behaviour out of Drupal. Squid believes that
there are hundreds of different versions of that page, all equally
likely to be validated and used as a response by the backend. We
probably want a cap on the number of variants we support, or at least
a knob to set it.

I'd look at your backend behaviour though - even with a knob, you're
still wasting a lot of processing.

-Rob
Received on Mon Apr 30 2012 - 11:37:15 MDT