Disable caching at specific times? ( and a deeper mystery )

Gaute Amundsen gaute at pht.no
Wed May 27 10:31:41 CEST 2009


We have this most peculiar problem where varnish somehow manages to cache a 
page with a Content-Type header with charset of utf-8 even though zope 
correctly answers  iso-8859-1 for every combination of request headers I can 
think of, when accessed directly.

The culprit must be some combination factors involving a spider, zope, apache 
and haproxy, we think, but we have not managed to reproduce the bug yet.

While we are digging into this mystery there is one important customer that 
always seem to run into this problem while publishing articles in the early 
morning hours.
What we need to do is simply return(pass) for this host outside of prime time.
We do this manually now, but that is way to easy to forget.
We could have zope handle it, but as normal ttl is 2 days, it would be much 
cleaner if it was possible to do in VCL.

My VCLfu, is not quite at that level yet :)

Any suggestions? Something involving the Client-Date header perhaps?

And any suggestions on the deeper mystery are most welcome as well of course.
Right now we are expanding logging, in the hope of catching the bug "in the 

Gaute Amundsen

Programmerer - Pixelhospitalet AS
Prinsessealleen 50, 0276 Oslo 
Tlf. 24 12 97 81 - 9074 7344

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