sporadic timeouts querying bind9

Klaus Darilion klaus.mailinglists at pernau.at
Mon Apr 23 12:55:47 UTC 2018

Hi all!

Upgrading to Ubuntu 16.04 with Bind 9.10.3 did not solved the problem.

I enabled debug log (trace 2) and query logging. Unless my monitoring
traffic (~20 Queries every second) the server is idle.

The server is a xen domU (on a idle hypervisor) with 4 vCPUs and 20G RAM.

Here the logs from my checker script:
Apr 23 10:35:17 tld-all-tst1 darilion: OK:
Apr 23 10:35:18 tld-all-tst1 darilion: OK:
Apr 23 10:35:24 tld-all-tst1 darilion: FAILED - timeout (3 sec) or
network error querying SOA for hu
Apr 23 10:35:31 tld-all-tst1 darilion: FAILED - timeout (3 sec) or
network error querying SOA for hu
Apr 23 10:35:32 tld-all-tst1 darilion: OK:
Apr 23 10:35:33 tld-all-tst1 darilion: OK:

Hence, no responses from Bind between 10:35:18 and 10:35:32

The debug log during this time is attached. It seems Bind hangs from
10:35:19.126 to 10:35:30.036, maybe at the end of writing the zone file.
The zone file is around 2.2G.

The query log also show nothing during this time:
23-Apr-2018 10:35:18.760 queries: info: client (at):
query: at IN SOA - (
23-Apr-2018 10:35:30.037 queries: info: client (hu):
query: hu IN SOA - (

Continuous Write performance of the disk is ~130MB/s. To me it seems
that Bind is somehow blocked at the end of the zone dump and hence not
answering queries anymore.

May this be possible? Is somewhere documented how Bind as slave applies
the incoming IXFR to the loaded zone, the journal .... Are there any
locking operations in bind?


Am 15.03.2018 um 14:45 schrieb Klaus Darilion:
> Hi!
> I use bind 9.9.5.dfsg-3ubuntu0.17 with around 20 slave zones (from small
> to huge).
> I query the SOA of every configured zone once a second to monitor bind.
> Once a day my script reports timeouts (3 seconds) querying a SOA. This
> server is a test server, hence it is idle except the monitoring checks.
> When inspecting the logs the timeouts are always very close to NOTIFYs
> and zone transfers. Are there any known issues that e.g. bind may
> suspend queries wile applying the zone transfer? Any other ideas what
> could be the reason?
> Thanks
> Klaus
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