Elastic Load Balancer as backend to Varnish

[Hugo Cisneiros (Eitch)]

On Fri, Apr 13, 2012 at 8:04 AM, Aaron de Souza
<aaron.desouza at roh.org.uk> wrote:
> Hi,
>
> I’m using Varnish 3.0.2 and my backend is an Amazon ELB so we can use the
> auto scaling features of AWS to add and remove instances from the load
> balancer.
>
> The problem is, is that if the backend load balancer is in multiple
> availability zones then it is given multiple IP addresses and varnish
> doesn’t like that

This won't be possible using Varnish, at least the usual way. When
varnish compiles its VCL (on startup or on vcl.load), it resolves the
DNS names from the backend's definitions and it keeps that way.
Because varnish is very much concerned about performance, it won't use
DNS lookups at run-time and can't accept multiple IP addresses on one
backend.

If you look through this mailing list history, you'll see a few people
(including me) wanting to do that, and some crazy solutions, like
recompiling and loading the VCL from time to time with multiple
backends and a director. But sadly there's no good and secure way to
do this. :(

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