[Pkg-utopia-maintainers] Bug#846381: avahi-daemon: cups frequently forgets about all printers untils restarting avahi-daemon

[Helmut Grohne]

On Mon, Jan 01, 2018 at 03:47:04PM +0000, Brian Potkin wrote:
> evince can get remote printer information from cups-browsed but, if the
> latter is not running, it browses the Bonjour broadcasts of servers and
> printers directly, just as avahi-browse does.

I cannot confirm the described behaviour.

> > > First things first. Are you still experiencing this behaviour on an
> > > up-to-date unstable/testing system?
> > 
> > Yes. I see this behaviour on stretch and sid.
> 
> I am working with sid. Are you using AppArmor on Stretch?

I have never explicitly enabled AppArmor. The stretch system is pretty
close to a standard installation. I haven't fiddled with it much.

The sid system certainly isn't using AppArmor and could have a few
oddities: It was installed as potato and upgraded since.

> Let's see whether cups-browsed has any connection with the issue. Stop
> it running and bring up evince. Its print dialog should show the remote
> printers it gets from mdns broadcasts. You relate the printers disappear
> a few times a day, so we shouldn't have to wait too long to see whether
> it happens in this situation. BTW, is there any discernable pattern to
> the behaviour? Time of day, time interval etc?

As soon as I stop cups-browsed, all printers disappear. The ppd files
are deleted. lpstat does not know them anymore and they disappear from
the evince print dialog (or don't show up there if I restart evince).
When cups-browsed is started again, the printers in evince, the ppd
files and the lpstat output is back again pretty much immediately.

Concerning the timing, I looked hard before filing the bug report. Log
rotation was something obvious to correlate it to, but without luck. The
waiting time seems exponentially distributed to me. Sometimes I had it
multiple times within an hour other times a day went by without.

When I ran the whole thing under strace, it didn't happen within 12h.

> Thanks for the offer. Have a good look at what journalctl says. Search
> for clues with "avahi", "audit", SIGTERM (and anything else you can
> think of).

I checked that much before the filing. I'm afraid we'll need to turn on
some more logging to get useful things here. Just what should I enable?
The manual page of avahi-daemon.conf is pretty scarce on debugging
options. cups-browsed logging is pretty much off by default and when you
enable it you only see the fact that printers get removed, not why.

You see, this issue is not easy to debug. I hope you can bear with me.

Helmut