[Pdns-users] Questions about failing over between multiple gmysql backends

Omar Buhidma pdns-users at placemark.com
Fri Jun 2 20:05:52 UTC 2006


I'm in the process of preimplementation testing on a pdns
implementation, using the gmysql backend.  I'd like some redundancy on
the backend, so I've configured pdns 2.9.20-1 with 2 gmysql backends.
This works quiet well, but isn't producing the behavior I'm interested
in seeing - when one of the mysql services goes down, pdns says:

Jun  2 14:39:01 primary-ns1 pdns[8191]: gmysql Connection succesful
Jun  2 14:39:01 primary-ns1 pdns[8191]: gmysql Connection failed: Unable
to connect to database: Can't connect to MySQL server on 'X.X.X.X' (111)
Jun  2 14:39:01 primary-ns1 pdns[8191]: Caught an exception
instantiating a backend, cleaning up
Jun  2 14:39:11 primary-ns1 pdns[8157]: Distributor misses a thread
(1<3), spawning new one

>From comparing these log entries to the actual traffic between the
machines, I've ascertained that pdns is trying to connect to both mysql
servers.  The first responds, the second does not.  Rather then merely
timing out the one connection, pdns queries both backends all the time.
 When one fails to respond, pdns itself doesn't return a result.

I've poured through the manual and been unable to identify a way to
alter this behavior.  I'd like pdns to be able to return a result from
one backend even when the other backend is unavailable.

How might I go about accomplishing this?

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