I'm having some odd trouble with DNSTAP output file rolling in BIND
9.12.0rc1.
I have named built like:
BIND 9.12.0rc1 <id:f9c3aba>
running on Linux x86_64 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt25-1
(2016-03-06)
built by make with 'STD_CDEFINES=-DISC_FACILITY=LOG_LOCAL5'
'--libdir=/usr/lib/x86_64-linux-gnu' '--with-openssl' '--enable-dnstap'
'--enable-fixed-rrset' '--disable-openssl-version-check' '--with-libtool'
'--enable-dnsrps'
compiled by GCC 6.3.0 20170516
compiled with OpenSSL version: OpenSSL 1.1.0f 25 May 2017
linked to OpenSSL version: OpenSSL 1.1.0f 25 May 2017
compiled with libxml2 version: 2.9.4
linked to libxml2 version: 20904
threads support is enabled
I have DNSTAP configured like:
dnstap {
client query;
};
dnstap-output file "tmp/dnstap.out" versions 10 size 10m;
It mostly works as expected, except that named:
o logs twice about rolling the file every time, such as:
Jan 2 05:15:42 named[24758]: dnstap: info: rolling dnstap
destination 'tmp/dnstap.out'
Jan 2 05:15:42 named[24758]: dnstap: info: rolling dnstap
destination 'tmp/dnstap.out'
o sometimes crashes after logging that, possibly after rolling the file
o writes to multiple output files simultaneously, such as:
ls -lt dnstap* | head -2
-rw-r--r-- 1 bind bind 1282048 Jan 2 16:24 dnstap.out
-rw-r--r-- 1 bind bind 1273856 Jan 2 16:24 dnstap.out.0
& 2 minutes later:
ls -lt dnstap* | head -2
-rw-r--r-- 1 bind bind 1286144 Jan 2 16:26 dnstap.out
-rw-r--r-- 1 bind bind 1277952 Jan 2 16:26 dnstap.out.0
This system had 4 worker threads in use. Another similar system with only 1
thread does not have such trouble, which got me wondering about problems with
threads & DNSTAP, specifically output file rolling. Reducing the threads on
the afflicted system (via named option "-n 1") seems to avoid the problem,
but it's a little early to tell, & it's not a desirable fix.
I'd appreciate it if somebody who knows the code would comment on the threads
vs DNSTAP possibility or point me in some other direction to figure this out.
I have a named core file & can provide more config... details if required.
________________________________________________________________________
Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
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