[Pdns-users] ddns performance of pdns

[Ruben d'Arco]

On Thu, Feb 25, 2016 at 07:54:26AM -0600, ktm at rice.edu wrote:
> On Thu, Feb 25, 2016 at 12:01:19PM +0100, Thomas Mieslinger wrote:
> > Hi,
> > 
> > today I wanted to migrate my ddns master from bind to pdns. 3 DHCP
> > Servers sent a about 50 updates per second to the pdns 3.4.8 and
> > only one or two updates per second could be successfully commited to
> > the database.
> > 
> > All failed transactions rolled back after trying to edit the SOA record.
> > 
> > I'm using 5.1.73-log MySQL Community Server.
> > 
> > I'm using REPEATABLE-READ transaction-isolation and
> > 
> > distributor-threads=2
> > receiver-threads=10
> > 
> > as pdns performance settings.
> > 
> > I tried to disable SOA-EDITs with domainmetadata
> > 
> > SOA-EDIT-DNSUPDATE   | SOA-EDIT
> > SOA-EDIT             | NONE
> > 
> > but that didn't change anything.
> > 
> > What DDNS performance do you get from your pdns instances with which
> > settings?
> > 
> > Thanks Thomas
> 
> Hi Thomas,
> 
> You will need to investigate your DB performance. Turn on query logging
> and slow query logging. Also check system I/O stats to see if you have
> a bottleneck there. We are just getting started on adding a DDNS component
> to our network so I do not have any firsthand experience with it and the
> queries it uses. Good luck in your hunt for the bottleneck.
> 
> Regards,
> Ken


Just to add to this, there is a lock for every update message. This is to avoid 2 update messages from causing some transactional issues.
There's also a comment above that lock that the lock might should be placed per zone, allowing multiple zones to be updated at the same time.

When i did some testing on this, it seemed that this was the limiting factor. It's just not fast if 1 update needs to wait for the other to be completed. But, at the time, i didn't check if this could be done better.

You mentioned that you have 3 dhcp servers - i'm assuming they all update the same zone?

Regards,
	Ruben