[Pdns-users] powerdns internals

Martin domains at crystalline.nl
Mon Nov 2 14:56:35 UTC 2015

I'm still struggling to solve this problem.
When I compare both backends (one a custom queries and one a regular) 
and the queries they send to MySQL for a nonexistent subdomain MX 
record, it appears they basically both send the same type of queries and 
get the same kind of results/rows back. The only difference is that the 
custom queries backend fires two more queries *after* the 'SOA-EDIT' 
query (see below, which is the final query the regular backend sends): 
it queries again for SOA records for abc.example.com and then 
example.com .
Is there any reason why a DNS client or Powerdns would fire these SOA 
queries again? It already got the SOA record from the first two queries 
(see below). Thanks again for any pointers.


On 01-11-2015 16:10, Martin wrote:
> Hi,
> It is somewhat helpful but doesn't solve my issues. I understand that
> to return NXDOMAIN my queries should not return data, but how can I do
> that when Powerdns uses ANY queries to fetch the data all the time?
> The only query types that I see in the MySQL logs are SOA, NS and ANY.
> If there are no MX records for abc.example.com but there is an A
> record for abc.example.com, my ANY query is never able to return 0
> rows. As I said, in that case I would expect Powerdns to filter out
> nonrelevant records.
> FWIW, here's the order of queries in the MySQL logs when, for example,
> I query a nonexistent TXT record for abc.example.com . I have only
> listed queries relevant for the backend the domain example.com is in,
> since the other backend successfully returns no data at all for that
> domain.
> type='SOA' AND domain='abc.example.com' => returns nothing
> type='SOA' AND domain='example.com' => returns 1 SOA record
> type='NS' => returns nothing (I'm not sure where this query is coming
> from because it resembles one of my custom queries but it is
> definitely not one of them?)
> ANY-ID query for abc.example.com => returns 1 row that contains an A 
> record
> PRESIGNED metadata query => returns nothing
> NSEC3PARAM metadata query => returns nothing
> type='SOA' AND domain='example.com' => returns 1 SOA record
> ANY-ID query for example.com => returns TXT record, 2 NS records, SOA
> record and an A record
> SOA-EDIT metadata query => returns nothing
> Martin
> On 30-10-2015 17:29, bert hubert wrote:
>> On Fri, Oct 30, 2015 at 04:07:13PM +0100, Martin wrote:
>>> Hi,
>>> I have a question about how Powerdns works internally after having
>>> read the documentation at
>>> https://doc.powerdns.com/md/authoritative/internals/
>> Martin,
>> Can you read
>> http://blog.powerdns.com/2015/06/23/what-is-a-powerdns-backend-and-how-do-i-make-it-send-an-nxdomain/
>> to see if it helps?
>> 	Bert
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