Public bug reported:
I'll start out by saying that I cannot _consistently_ reproduce this (it
is, after all, a race condition), however the fix is trivial and a no-
op, so I'm filing the bug anyway.
I ran into the following situation on Ubuntu 14.04: After booting, it
was often the case that CUPS would not be running. CUPS started just
fine if started by hand, and there were no obvious causes of this in the
syslog. However, the times when CUPS was not running, I noticed the
boot process seemed to be a bit more sluggish than usual. I eventually
tracked this down to the avahi-cups-reload job, which unconditionally
kicks CUPS once avahi has been started, with no regard for whether CUPS
is actually running. As soon as I moved that Upstart job out of the
way, the problems vanished. My particular issue stems from the fact
that our site also has another init script that attempts to ensure CUPS
is running (and restarts it if not), and much of the time, this was
happening while avahi-cups-reload was attempting to reload CUPS. This
resulted in CUPS eventually failing to restart (because the post-start
script in the CUPS job determined CUPS wasn't running, and exited 0.),
which Upstart interpreted as success, and therefore assumed that CUPS
was in fact running.
I realize this is quite a specific problem, and may well be unique to
our site, but is there any reason why the the avahi-cups-reload job
cannot change its condition from:
start on started avahi-daemon
to
start on (started avahi-daemon and started cups)
which also seems to fix the problem for me, by at least ensuring things
start in an orderly manner. (There may well be a subtle Upstart bug
here too, but this seems like an easy fix.) See also, Launchpad
#1251735, where someone else appears to be experiencing a variant of
this issue, and is also requesting the same fix.
Relevant info:
avahi-daemon:
Installed: 0.6.31-4ubuntu1
Candidate: 0.6.31-4ubuntu1
Version table:
*** 0.6.31-4ubuntu1 0
500 http://mirrors.mit.edu/ubuntu/ trusty/main amd64 Packages
100 /var/lib/dpkg/status
cups-daemon:
Installed: 1.7.2-0ubuntu1
Candidate: 1.7.2-0ubuntu1
Version table:
*** 1.7.2-0ubuntu1 0
500 http://mirrors.mit.edu/ubuntu/ trusty/main amd64 Packages
100 /var/lib/dpkg/status
upstart:
Installed: 1.12.1-0ubuntu4
Candidate: 1.12.1-0ubuntu4
Version table:
*** 1.12.1-0ubuntu4 0
500 http://mirrors.mit.edu/ubuntu/ trusty/main amd64 Packages
100 /var/lib/dpkg/status
** Affects: avahi (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1332131
Title:
avahi-cups-reload Upstart job leads to weird race conditions
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