[Pdns-users] Limit on TCP querys.

Grant Keller gkeller at corp.sonic.net
Mon Dec 5 20:24:20 UTC 2011

On 12/04/2011 10:17 PM, Peter van Dijk wrote:
> Hi Grant,
> On Dec 4, 2011, at 21:44 , Grant Keller wrote:
>> On 12/03/2011 10:40 AM, Peter van Dijk wrote:
>>> Hello Grant,
>>> On Dec 3, 2011, at 1:14 , Grant Keller wrote:
>>>> When I run a large number of querys against my PDNS 3.0 auth server, I am seeing a number of timeouts on my querys. For example, if I run 19000 tcp querys at 5-6 querys per second, I end up with about 400 querys failed due to timeouts.  Most of the time outs occur in batches, where I see all querys or every other query timeout. Is that simply too many tcp querys for PDNS to handle?
>>> Depending on how you are doing this, you may be hitting the max-tcp-connections default, which is 10. If you want to do lots of TCP queries, I suggest increasing max-tcp-connections a lot.
>>> Kind regards,
>>> Peter van Dijk
>> The max-tcp-connection was set to 1000, and figured that would be high enough, should I increase the limit further?
> 1000 sounds like it should be enough. Can you share how you are running these queries? And is PowerDNS logging anything during your tests, especially around times of failure?
> Kind regards,
> Peter van Dijk

  A quick and dirty perl script runs the querys, using 
Net::DNS::Resolver to run tcp querys with a timeout set to 1 second:


the list of domains I use is located here:


One thing to note is that these are all domains the server is 
authoritative for, and it is looking up the A record of each.

The server I am running the querys against is granttest.noc.sonic.net, 
which is a test box with no other traffic. If you need any more info, 
let me know.
Grant Keller

More information about the Pdns-users mailing list