Varnish 500's now not 302's

[Nicholas_Maesepp at scee.net]

Nothing special about my config file apart from the hashing of objects, I 
do have the following already in my vcl_fetch:

set beresp.grace = 3m;
if (beresp.status == 500) {
    set beresp.saintmode = 5s;
  }

======
vcl_recv {
set req.grace = 40s;
if (req.request != "GET" && req.request != "HEAD") {
         /* We only deal with GET and HEAD by default */
         return (pass);
     }
if (req.http.Accept-Encoding && req.url ~ "\.(png|gif|jpg|swf|mov|flv)$") 
{
        remove req.http.Accept-Encoding;
  }
return (lookup);

I'm not convinced that I'm caching 500 responses on all these objects, I 
do wonder if its because I remove accept-encoding on those objects, those 
are the ones that end up with 500's. But also maybe my saintmode and grace 
numbers are too low if the back-end is infact serving 500's. But at least 
it's an avenue to explore and get some evidence to prove or disprove it. 
Will also try using hit for pass instead and see if that gives me more 
resilience.


Cheers

Nick




From:   Hugues Alary <hugues.alary at gmail.com>
To:     Andreas Plesner Jacobsen <apj at mutt.dk>
Cc:     varnish-misc at varnish-cache.org
Date:   05/12/2012 03:29 AM
Subject:        Re: Varnish 500's now not 302's
Sent by:        varnish-misc-bounces at varnish-cache.org



At this point, sending your configuration file would maybe be a good idea.
On May 11, 2012 1:41 AM, "Andreas Plesner Jacobsen" <apj at mutt.dk> wrote:
On Fri, May 11, 2012 at 09:30:52AM +1100, Nicholas_Maesepp at scee.net wrote:

> I guess technically I realize this is from the cache, my question is 
more
> along the lines of what could be causing my objects in the cache to 
become
> stop being delivered as is and having a 500 error returned. Is my cache
> being corrupted in some way when varnish starts to max out the malloc'ed
> RAM? Seems like a bug to me but can't pinpoint exactly what causes it,
> just that it happens after X amount of time to any of my instances.

Then you misunderstood me. The 500 is a cached object that your backend 
served
at the time. You can avoid caching such objects by inspecting the HTTP 
response
in vcl_fetch and setting TTL and/or using hit for pass and/or saint mode.

It's almost certainly not a bug.

--
Andreas





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