Random slow queries
Stacey Jonathan Marshall
Stacey.Marshall at Sun.COM
Thu Feb 25 11:01:55 UTC 2010
On 02/24/10 18:50, Mike Chesney wrote:
> Running Bind 9.6.1-P3
>
> We run authorative DNS for 60k+ zones. One one network where we two
> dns servers both running the same hardware on Centos 5.4
>
> We see slow dns responses : example
>
> for i in {1..250}; do dig example.com <http://example.com> @localhost
> | grep "Query time:"; done;
Centos is a time-sharing system right. I wonder if your time-share is
up and your simply being scheduled off CPU - the network communication
is an opportunity for the scheduler to do that.
Try adding a sleep and see if your results smooth out - more 0 msec and
less msec total.
for i in {1..250}; do sleep 0.5; dig example.com <http://example.com> @localhost | grep "Query time:"; done;
> Sometimes they'll all come back w/ a 0msec response . But every few
> runs we see.
> ; Query time: 501 msec
> ;; Query time: 111 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 1461 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 441 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
> ;; Query time: 0 msec
>
> This is just a snapshot, most other entries are all 0. This doesn't
> happen on any of our other dns servers. Load is pretty low on this
> machine around .3 4gb ram. Named consumes about 15% of memory and
> 4% of cpu. Not sure where to look next.
>
>
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