Hostnames in backend definition...

Poul-Henning Kamp phk at
Thu Dec 15 01:26:13 CET 2011

In message <CB0E7D6E.1A1F7%mhettwer at>, "Hettwer, Marian" writes:

>>We have talked about having the health-probe do DNS lookups in the
>>background, but there are some interesting cornercases that needs
>>to be dealt with, for instance:  What happens when we suddenly get
>>two IP#'s back, or when we get no ip numbers back.
>But as you said, you had your talks about it, so I guess the decision is
>settled for now.

No, not really:  Absent a consistent proposal on how it should work,
we have not changed anything yet.

Ideas are always welcome, but they need to be thought through and all
the odd-ball cases considered if we are to adobt them.

>I can understand this. On the other hand, even in your own datacenter
>setup, one might need to change dns records. Restarting a service for that
>is just... Well... painful.

You don't need to restart any service:  Just load your VCL again and
switch to the newly loaded VCL and you won't see your service as much
as blink.

Varnish was built to do that kind of change on the fly, and we're
proud of how well it works.

>So that's the reason why there's so much OSS around which just plain
>caches DNS forever after startup?


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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