Backend DNS lookup refresh

Marc Fournier marc.fournier at
Sun Nov 6 11:56:05 CET 2011

Hello Thierry,

Excerpts from MAGNIEN, Thierry's message of Thu Nov 03 17:14:50 +0100 2011:
> We are dealing with a great number of backends in our VCL file and we
> have problems with some backends changing IP address (for example when
> hosted on services such as Amazon S3, that switch IP address without
> telling anyone).

A couple of years ago, we worked around the specific case of S3 by putting
a simple nginx proxy between S3 and varnish.

Amazon S3 emits HTTP redirects when DNS changes occur[¹]. Unfortunately
varnish doesn't handle them either. But nginx does, as well as backend DNS

It doesn't really answer your question, but this somewhat ugly workaround
has been working very reliably for us since then. It would be nicer if
varnish could deal with these 2 cases, though.



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