[Pdns-users] pdns_recursor : cpu usage with 2.9.20-563 & stats questions

Gavarret, David david.gavarret at neufcegetel.fr
Sat Feb 25 14:56:30 UTC 2006

Hi all,

We use since few weeks pdns_recursor on some of our resolvers servers for 
our residential customers (I was looking for a long time for an alternative 
to Bind and others for that job).
I tested versions 2.9.18 and 2.9.20 snapshot 563.
These servers serve between 150 and 700 qu/sec (with a 70% cache hit ratio), 
and are powered by Xeon 3.2G with 3G RAM, under Linux 2.6.12 (any comment 
concerning hardware sizing is welcomed).

With 2.9.18, CPU usage never raised above 10% during 3 weeks, with a 
constant capacity to answer queries.
But with the last snapshot, CPU raised to 100% in 5 days, and qu/sec dropped 
under 100 qu/sec (on all servers with 2.9.20-563)
Did some of you have the same behaviour with snapshot 563 ?

My other question is about monitoring ans stats retrieving.
I have to graph servers' activity (mainly queries/sec and cache hit ratio) 
by the mean of a snmp agent. Because of the syslog problem in daemon mode, I 
run pdns_recursor as a foreground task with stdout piped to logger ... But 
the delay between the SIGUSR1 and the output of statistics forced me to 
write a little daemon to "anticipate" the snmp polling by sending SIGUSR1 
repeatedly few seconds before and until the next estimated polling and store 
them to a file read by the snmp agent ... obviously not the easier way :)
What are your methods do get stats by a snmp polling ?

Thank you in advance :)

David Gavarret 

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