[Pdns-users] Using AXFR vs. Mysql Replication

[Lorens Kockum]

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.