[Pdns-users] 5001 questions waiting for database attention. Limit is 5000, respawning

[bert hubert]

On Wed, Aug 19, 2015 at 09:29:26AM -0400, Stan Weatherby wrote:
> Hello,
> 
> We are experiencing a very strange issue. Our PDNSD servers keep getting
> the error: 5001 questions waiting for database attention.  Limit is 5000,
> respawning which is killing the answer side.

Hi Stan,

This can happen regardless of backend. If your pipe backend is blocking or
slow, you would get this. The error message is confusing in that it mentions
'database' and not 'backend'. I've changed this in
https://github.com/PowerDNS/pdns/commit/3172f9b6c35de2dd05b3a8abe6312f67e4c9f5fa

What you could do is hook up your PowerDNS to
http://blog.powerdns.com/2014/12/11/powerdns-graphing-as-a-service/ which
will provide a lot of insight into what might be going on.

> Here is the strange thing, we are not using the MySQL backend, we are
> using the pipe backend and running heavy cache.  In the config file we do
> not ask to load MySQL just “pipe”, has anyone else experienced this issue? 
> We see this happen on loads of about 50 requests per second CPU - RAM -
> and all other system resources are running at a nominal load.

At a guess, your pipe backend is blocking on something.

> Maybe we are missing some performance tuning? Still wondering why PDNSD is looking for the DB.

No worries, it isn't looking for a db.  Our error was just confusing.

	Bert