Bug#993051: avahi-daemon CPU usage increases over time

[Andreas Schneider]

I have the exact same problem for quite some time already (certainly 6
months, likely more), using Debian sid.

I'm surprised that this bug report is the only mention of the issue I could
find on the net. It's reproducible every time I switch on my printer, but
it takes quite some hours, in the order of a few days, before it turns into
a significant problem. Running `sudo avahi-daemon -k` kills the process and
a new one is started, which behaves well until I switch on my printer.

It looks like Ryan already did what I was planning to do, i.e. debug
through the daemon and do some Monte Carlo profiling. If there is anything
I can do to help triage the problem, please let me know. For now I can only
share details of my home setup that may or may not be helpful: the printer
is an HP Deskjet-3630; DNS is handled by a FritzBox! but I believe the
issue also showed up while I was using my home grown dnsmasq server.

Best,

Andreas

Bug#993051: avahi-daemon CPU usage increases over time

[Ryan Armstrong]

Package: avahi-daemon
Version: 0.8-5
Severity: normal

Dear Maintainer,

After upgrading to Debian Bullseye, I noticed that the Avahi CPU usage on my 
server machine was
quite high (eventually 100% of one core). After resetting Avahi, the CPU usage 
was normal then
eventually increased over time again until it was again rather high. The
increase appears to be (very roughly) 1 or 2% per hour on my rather humble 
Intel(R) Celeron(R)
CPU 4205U @ 1.80GHz.

Checking the journal, I only see the following sorts of lines:

Aug 25 16:21:30 zeta avahi-daemon[31]: avahi_normalize_name() failed.
Aug 25 16:21:30 zeta avahi-daemon[31]: avahi_key_new() failed.
Aug 25 16:21:30 zeta avahi-daemon[31]: avahi_normalize_name() failed.
Aug 25 16:21:30 zeta avahi-daemon[31]: avahi_key_new() failed.
Aug 25 16:21:31 zeta avahi-daemon[31]: avahi_normalize_name() failed.
Aug 25 16:21:31 zeta avahi-daemon[31]: avahi_key_new() failed.

Which was around the time I turned on another machine on my network.
However, the timing was not aligned with when Avahi CPU usage increased.
Instead, it seems to be aligned with when I turn on my printer, but nothing
of note was printed in the log when that happened.

Is there any means for me to gather additional information to help
diagnose this problem?

Thanks,
Ryan

-- System Information:
Debian Release: 11.0
  APT prefers stable-security
  APT policy: (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.10.0-8-amd64 (SMP w/2 CPU threads)
Locale: LANG=en_CA.UTF-8, LC_CTYPE=en_CA.UTF-8 (charmap=UTF-8), 
LANGUAGE=en_CA:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages avahi-daemon depends on:
ii  adduser  3.118
ii  bind9-host [host]1:9.16.15-1
ii  dbus 1.12.20-2
ii  init-system-helpers  1.60
ii  libavahi-common3 0.8-5
ii  libavahi-core7   0.8-5
ii  libc62.31-13
ii  libcap2  1:2.44-1
ii  libdaemon0   0.14-7.1
ii  libdbus-1-3  1.12.20-2
ii  libexpat12.2.10-2
ii  lsb-base 11.1.0

Versions of packages avahi-daemon recommends:
ii  libnss-mdns  0.14.1-2

Versions of packages avahi-daemon suggests:
pn  avahi-autoipd  

-- no debconf information