[Pdns-users] Dealing with high concurrency and MySQL backend

Aki Tuomi cmouse at youzen.ext.b2.fi
Wed Sep 21 18:39:51 UTC 2011

On Wed, Sep 21, 2011 at 02:35:44PM -0400, Mohamed Lrhazi wrote:
> Hello,
> I run a resperf test against a fresh setup of
> pdns-2.9.22-10.el6.x86_64, on CentOS 6, on an ESX VM with 2vCPUs and 2
> mysql is: mysql-server-5.1.52-1.el6_0.1.x86_64, all rpms from EPEL,
> with no tweaks of configs....
> The respserf is using a query file made up of all my records, about
> 50,000, duplicated several times to make it a bit over a million
> lines.
> pdns crashes with error:
> 5003 questions waiting for database attention. Limit is 5000, respawning
> Is it possible to tweak MySQL (InnoDB) to handle such load?
> What would be my options, in order to perform well under such high
> amount of concurrent queries? Is MySQL an option at all?
> Could pdns caching help? Could one warm it up somehow so as to load
> the intire data set into the cache? Would that be serious for real
> world traffic?
> Thanks a lot.
> Mohamed.

You can find several documents on how to improve MySQL InnoDB performance. 
What you want is to keep as much as possible in the memory, although the 
tweaks do not necessarely make it simple or easy to understand.

Also, make sure you have indexes properly set in your schema. If your indexing
is wrong, it will cause sever deterioration of performance. 

Aki Tuomi
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