Failover
Sam Wilson
Sam.Wilson at ed.ac.uk
Mon Apr 27 09:33:04 UTC 2009
In article <gt3l6f$17m9$1 at sf1.isc.org>, <Philippe.Simonet at swisscom.com>
wrote:
> This is not the DNS job to check at the web service availability.
> You could make an external script that is testing for the service availibil=
> ity
> and change the dns accordingly, like (...) :
>
> web1 active ?
> yes : was it active at last test ?
> yes : do nothing
> no : set www to point to web1 in DNS
> no : was it already inactive ?
> yes : do nothing
> no : set www to point to web2 in DNS
>
> and with having www/web1/web2 having a low TTL.
We do something like this for some not-very-critical services. A script
(happens to run on a nameserver, but that's coincidental) watchdogs a
number of servers and uses (suitably secured) dynamic update to remove
non-responsive ones from a low-TTL roundrobin. It knows not to remove
the last entry.
Sam
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