Varnish stuck on most served content

Diego Roccia diego.roccia at
Thu Mar 31 10:33:02 CEST 2011

On 03/30/2011 06:27 PM, Hauke Lampe wrote:
> Hash: SHA1
> On 30.03.2011 10:51, Diego Roccia wrote:
>> Varnish servers are HP DL360 G6 with 66Gb RAM and 4 Quad-Core Xeon CPUs,
>> running varnish 2.1.6 (Updated from 2.0.5 1 month ago).
> varnish 2.1.6 hasn't been released, yet, AFAIK.

Sorry, I meant varnish-2.1.5 (SVN 0843d7a), the version from official 
rpm repository
>> It's happening often that they freeze serving contents. and I noticed a
>> common pattern: the content that get stuck is always one of the most
>> served, like a css or js file, or some component of the page layout,
> Do you run 2.1.4 or 2.1.5? Is the "freeze" a constant timeout, i.e. does
> it eventually deliver the content after the same period of time?

Doesn't seems to be a constant time. the same varnish provides tens of 
elements per page, and sometimes it gets stuck on one of them. It's 
always a css or js. There are no rules in the vcl specific to these kind 
of files. so the only common pattern I see is that they're the files it 
has to serve most times.

> There was a bug in 2.1.4 that could lead to the symptoms you describe.
> If the client sent an If-Modified-Since: header and the backend returned
> a 304 response, varnish would wait on the backend connection until
> "first_byte_timeout" elapsed.

I don't think it's receiving the If-Modified-Since , as we're talking 
about website monitoring tools, and they are configured to start cache 
cleared every time.

> In that case, the following VCL code helps:
> sub vcl_pass {
> 	unset bereq.http.if-modified-since;
> 	unset bereq.http.if-none-match;
> }
> See also this thread:
> Hauke.
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> =BTfX

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