[Pdns-users] stuck tcp sessions on recursor

Kenneth Marshall ktm at rice.edu
Thu Feb 24 18:23:48 UTC 2011

On Thu, Feb 24, 2011 at 01:20:13PM -0500, Charles Sprickman wrote:
> Howdy,
> I'm seeing an issue with tcp queries on powerdns recursor 3.2.  We run two 
> instances of pdns recursor on an internal network and it's mainly hit by 
> lots of qmail delivery servers.  They are doing a ton of lookups, I think 
> we peak around 4000 queries/second.  With more people using dnssec, many 
> providers returning insanely huge lists of mxers, and qmail's propensity 
> for "any" queries, we're finding that our tcp queries are going way up.
> What we are seeing is that when "max-tcp-clients" is exceeded, it appears 
> that pdns is not properly closing sockets.  We then get a pile-up of 
> qmail-remotes that are "stuck" and deliveries stop until pdns is restarted. 
>  netstat shows the connections in state "CLOSED".
> We're running FreeBSD 8.1 on all the hosts involved.  This mailing list 
> post is interesting, and explains why these "CLOSED" sockets are in that 
> state:
> http://lists.freebsd.org/pipermail/freebsd-net/2008-June/018544.html
> Any pointers on how to troubleshoot this further?
> Thanks,
> Charles

There is not much to troubleshoot. This is a known bug. Try running
the latest release instead. They really do fix bugs. :)


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