On Mon, Apr 30, 2012 at 11:32 PM, Andy Taylor <andy@xxxxxxxxxx> 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
