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

[Brian Potkin]

On Tue 02 Jan 2018 at 10:13:01 +0100, Helmut Grohne wrote:

> 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.

The print dialog is empty when cups-browsed is stopped? Mystifying! GTK+
uses the avahi library to list printers and print queues advertised by
the DNS-SD protocol.

https://bugzilla.gnome.org/show_bug.cgi?id=688956

You have attained a goal others have striven for. :)

https://lists.debian.org/debian-user/2017/09/msg00980.html

> > > > 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.

Just ruling out AppArmor. It would have to be explicitly installed on
stretch....

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

...but not on unstable as it is a Recommends: of linux-image.

> > 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.

I hate it when events are random.
 
> 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 appear to have exhausted all the options I would suggest.
 
> You see, this issue is not easy to debug. I hope you can bear with me.

My interest in this bug arises from its affecting cups-daemon and my
knowledge of avahi is not great. It seems avahi-daemon stops providing
cups-browsed with information and the printer list would disappear, of
course. I would have been interesting to find out if the same thing
happens with the GTK dialog.

Cheers,

Brian.
> 
> Helmut