Strategies for splitting load across varnish instances? And avoiding single-point-of-failure?

Poul-Henning Kamp phk at
Sat Jan 16 18:22:16 CET 2010

In message <d002c4031001160741q63dd5a50i6342116daba159a6 at>, Micha
el Fischer writes:

>On Sat, Jan 16, 2010 at 1:59 AM, Poul-Henning Kamp <phk at>wrote:
>>        director h1 hash {
>>                { .backend webserver; .weight 1; }
>>                { .backend varnish2; .weight 1; }
>>                { .backend varnish3; .weight 1; }
>What happens when varnish2 or varnish3 dies?

If a particular backend in the director is unhealthy, the requests
for it will be redistributed by rehashing over the healthy subset
of directors.  Once it becomes healthy, normality will be restored.

So everything should work out fine, for some value around 99.9% of fine.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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