Re: recursive-clients queue size & clean-up

[Ladislav Vobr]

| Does each slot in the recursive-client queue being clean up after the
| timeout expire, if there is no response? Or some slots are being
| occupied longer, it seems to me that when I reach this limit there is no
| really way back to stabilize bind, all cpu will be used and even if I
| leave it over night when the traffic sometimes goes as little as 300-400
| req/sec it will not recover and still the messages keeps coming from
| time to time, cpu is very high (abnormal to the number of incoming
| requests) and number of requests logged to the query.log file is almost
| just half of what the box is really suppose to receive, (looks like bind
| or os dropping the traffic).
| There is no weird traffic, maybe there was a weird spike, but it should
| recover. When I stop and start service resumes, cpu drops, traffic
| comes back to normal rate, not almost like half rate as it was during
| the problem, and recursive-client queue is not overflowed.

We have seen similar problems. Our current conclusion is that BIND9 is
not very good as a recursive name server, and that it probably has bugs
involving large cache sizes and/or high query rates. We are currently
evaluating Nominum CNS, which so far seems to perform *much* better.
Nominum CNS is not free, of course...

Steinar Haug, Nethelp consulting, sthaug@nethelp.no