[Pdns-users] ddns performance of pdns

Thomas Mieslinger miesi at pc-h.de
Thu Feb 25 20:19:44 UTC 2016

Hi altogether,

thank you for sharing your thoughts.

I did some testing. The records table has around 115k rows. When I send 
single updates for a zone that has ~20 rows (out of the 100k) I get 
about 100 updates per second (what would be sufficient in my use case). 
When the zone to be updated has 80k records I only get 1 ddns update per 

I activated the mysql query log and analyzed (explain) them. All 
statements use the indexes and, when running them individually, they 
perform well.

I will review my mysql configuration if there is optimization possible. 
Maybe the query cache is to small or something else.



Am 25.02.2016 um 18:25 schrieb 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             | 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
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