Maintained by: NLnet Labs

[Unbound-users] Unbound stops responding

Petter Lindgren
Fri Aug 16 14:38:53 CEST 2013


We've used Unbound for a few months for around 15 000 clients I our company.

We recently had an issue when our Internet provider had a big network error.
This meant that our three unbound resolvers couldn't perform recursion.

But during the outage, they stopped responding to any queries and the CPU spiked.
This meant that we couldn't resolve local names.
After the outage was resolved, they started responding as usual again.

Statistics before outage:
2013-08-14 11:40:21 unbound[1180:0] info: server stats for thread 0: 137441 queries, 107082 answers from cache, 30359 recursions, 0 prefetch
2013-08-14 11:40:21 unbound[1180:0] info: server stats for thread 0: requestlist max 38 avg 4.54215 exceeded 0 jostled 0
2013-08-14 11:40:21 unbound[1180:0] info: average recursion processing time 0.120068 sec
2013-08-14 11:40:21 unbound[1180:0] info: histogram of recursion processing times
2013-08-14 11:40:21 unbound[1180:0] info: [25%]=0.00974991 median[50%]=0.0314827 [75%]=0.162277

Statistics during outage:
2013-08-14 12:40:21 unbound[1180:0] info: server stats for thread 0: 717834 queries, 79368 answers from cache, 638466 recursions, 0 prefetch
2013-08-14 12:40:21 unbound[1180:0] info: server stats for thread 0: requestlist max 893 avg 649.479 exceeded 520726 jostled 90153
2013-08-14 12:40:21 unbound[1180:0] info: average recursion processing time 16.060234 sec
2013-08-14 12:40:21 unbound[1180:0] info: histogram of recursion processing times
2013-08-14 12:40:21 unbound[1180:0] info: [25%]=0.0128234 median[50%]=0.046963 [75%]=0.241531


What can I do to make sure that Unbound still responds to a local query when there is an outage?

We run Unbound on Windows Server 2012 x64 (because we have more competence using Windows)

Is it possible to overcome the 1024 limit for outgoing-range and num-queries-per-thread when running Windows and would it have helped?

I would really appreciate comments and suggestions!

Thanks!

_________________________________________
Petter Lindgren

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