Hash director and backend health

Ken Brownfield kbrownfield at google.com
Tue Aug 2 02:47:58 CEST 2011

You could have the hash backends each be individual round/random directors
with your intended server having a very high weight and your intended backup
backend a weight of 1.  Awkward and somewhat lengthy, but it works.  The
only downside is that the fallback will get a non-zero amount of traffic.

director example hash {
       .retries = 5;
       { .backend = server1d; .weight = 1; }
       { .backend = server8d; .weight = 1; }

director server1d random {
       { .backend = server1;   .weight = 10000000; }
       { .backend = fallback1; .weight = 1; }

Yes, I believe the hash director is strict and ignores health, at least when
I played with it (very) briefly.

At some point in Varnish's future, it would probably be worth implementing a
backup backend at the director or even backend level.  Or at least a
fallback director/backend for hash, but the former is a more general

On Mon, Aug 1, 2011 at 00:35, Thiago Figueiro <TFigueiro at au.westfield.com>wrote:

> KT Sin wrote:
> > try adding backend probes. see:
> > https://www.varnish-cache.org/trac/wiki/BackendPolling
> Yep, they're there.
> Thanks tho.
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