pkg: Cannot get a read lock on a database, it is locked by another process

[Kevin Oberman]

On Mon, Jul 28, 2014 at 8:34 AM, Kris Moore <kris at pcbsd.org> wrote:

> On 07/27/2014 10:51, Stefan Esser wrote:
> > The locking of the pkg database leads to soft failures, but I'm afraid,
> > if these soft failures happen to coincide with certain administrative
> > tasks, they can lead to unexpected results.
> >
> > One example is that portmaster fails to detect PKGNG (and then assumes
> > to be working in a pre-PKGNG environment), if some pkg subcommand locks
> > the database. To repeat:
> >
> > # pkg version -Bs &
> > # pkg info
> >
> > As long as pkg version runs, pkg info fails to get the read lock (at
> > least in the large majority of my tests). You can also prevent any pkg
> > command from running, if you STOP (kill -STOP / ^Z) pkg version. Any
> > other pkg command will fail, until "pkg version" has been "unstopped"
> > and run to completion. This might even be a local DoS, if any command
> > that read-locks the package DB for extended time can be executed by
> > an unprivileged user.
> >
> > Similar error messages are reported by pkg_libcheck, which issues
> > lots of pkg commands in parallel. (I have observed some 5 lock
> > failures per 1000 installed packages on my system).
> >
> >
> > I did not try to test all combinations of simultanous pkg commands
> > and did not verify, whether e.g. "pkg upgrade" might be stopped
> > half way through because of an error accessing the pkg database,
> > but I have seen SQLITE error messages that indicated failed write
> > operations (INSERT/UPDATE).
> >
> > Either the timeouts are too low, or the duration during which the
> > database is locked by a single operation is too large (or there is
> > no fairness and some processes never get access to the database?).
> >
> >
> > I think this should be fixed, since pkg commands that lock the
> > database can be run from CRON or by other means in the background
> > and the operator who issues pkg commands in the foreground (or runs
> > portmaster) receives spurious error messages (which might still be
> > better than the batch jobs doing silly things, after they failed to
> > obtain information from the pkg database ...)
> >
> > Regards, STefan
> > _______________________________________________
> > freebsd-ports at freebsd.org mailing list
> > http://lists.freebsd.org/mailman/listinfo/freebsd-ports
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>
> +1 to this whole thing.
>
> I would prefer that pkg commands simply wait for the DB to become
> unlocked again, instead of just failing outright.
>
> We have many scripts which monitor the system, check for updates,
> display our GUI store-front, and its really annoying to have random bits
> of it fail simply because of bad timing with another pkg process.
>
> --
> Kris Moore
> PC-BSD Software
> iXsystems


This is a real pain, but I only see it on one of my systems. That system is
my only i386 system and also my only system running 9.2. Whether that has
anything to do with it, I can't say, but it makes me very nervous. I just
would like to know why only the one system has the problem.
--
R. Kevin Oberman, Network Engineer, Retired
E-mail: rkoberman at gmail.com