[Pdns-users] Using AXFR vs. Mysql Replication

Max Clark max.clark at gmail.com
Fri Jun 23 17:37:22 UTC 2006

So the general consensus seems to be AXFR replication is not a good
idea. We've lost name resolution a couple of times now because of
issues with Mysql replication (and once because mysql went down
causing the nameservers to go down, which caused name resolution for
client access to fail when we tried to bring the nameservers back up -
really stupid problem).

Outside of pulling the zones into tinydns format and replicating that
- is there another option that I should be looking at?


On 6/22/06, Lorens Kockum <lorens-pdns-3987 at tagged.lorens.org> wrote:
> On Thu, Jun 22, 2006 at 04:48:23PM -0400, Duane wrote:
> > Lorens Kockum wrote:
> > >    The pdns server does not remember AXFRs or SOA checks so
> > >    that it can re-NOTIFY the slaves who have not AXFRd a given
> > >    zone within some reasonable time. This means that if for
> > >    some reason an UDP NOTIFY packet is lost, the zone wil not
> > >    be updated, and if the NOTIFY is the initial one, the zone
> > >    will not be configured on the slaves until the zone is
> > >    changed and a new NOTIFY is sent.
> >
> > No but slaves track it and update themselves periodically.
> Unless it's the very first packet, in which case the slave doesn't know
> that it's supposed to track the domain.
> Also, you have a trade-off between the load imposed by slaves
> polling server for each and every domain "periodically",
> and the length of the "periodically", which should be short
> enough to make clients happy. I don't think "your domain isn't
> working because our slave failed to update from the master" is
> a good argument, so the period between checks in the absence
> of notifies would need to be, what, five minutes? Ten? Say ten
> minutes, for ten thousand domains that's two thousand packets a
> minute just for checking that nothing's changed, which IMHO is a
> bit steep.
> Of course there *are* notifies, but I seem to lose them
> regularly :-)
> > >    When a zone is removed from the master, the slave does not
> > >    recognize that. I would like the slave to remove the zone
> > >    from the database when it expires.
> >
> > This can be fixed using a shell script
> Yes.
> > there are other problems with
> > the AXFR mechanism, but these are mostly non-issues.
> Agreed.
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Max Clark

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