[Pdns-users] tracking servers through database backend?

Amos Shapira amos.shapira at gmail.com
Thu May 10 06:15:59 UTC 2007

On 10/05/07, bert hubert <bert.hubert at netherlabs.nl> wrote:
> On Thu, May 10, 2007 at 02:22:42PM +1000, Amos Shapira wrote:
> > 1. A Geo backend which will pick a CNAME record based on the IP from
> which
> > the query came.
> > 2. A database backend (MySQL/PostgresSQL) which will resolve the name
> that
> > the CNAME points to into an IP address.
> >
> > I wonder if that I wrote until here makes sense.
> Very much so!
> > Now the twist is that I was thinking of having a specialised program
> which
> > probes all the available servers, checks that they are still alive and
> well,
> > and updates the records of the database back-end whenever a server's
> > availablity changes.
> This is one easy way of doing things, and it would work fine.
> > Is this a possible plan?  How do others setup such networks?
> > e.g. I read the Wikipedia uses PowerDNS with GeoIP to forward users to
> > nearer servers, but does it also check whether the node or cluster it
> > forwards the user to is available at all?
> There are no special checks for the Wikipedia. Some other PowerDNS users
> have used a special 'pipe' backend to do realtime checks of server
> availability, but changing the database on server availability changes
> works
> as well.
> Good luck!

Thanks very much for the feedback. It helps a lot to my trust in my plan.

About the pipe backend - it sounds awfully slow to do such "realtime" checks
(at least in my case - the servers could be halfway around the world). If I
read the docs correctly then PDNS is smart enough to cache the results so
not all clients will be hit by a check, only the first one - is this


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