Re: [SSI-users] postgresql and load balancing

[Roger T. <rog...@gm...>]

The errors don't say whether it is something to do with POSIX locks. POSIX
locks are cluster wide and so are semaphores.

In the case of POSIX locks OpenSSI has a bug that can race across the
cluster. That is when two or more processes on different nodes fight over
the same file lock there is no guarantee they will be served in the order
their requests were submitted. They are served in the order their requests
arrive at the CFS server the file belongs to.  A possible fix is to
serialize the requests by timestamp.
On Feb 17, 2013 12:48 AM, "Mulyadi Santosa" <mul...@gm...>
wrote:

> On Fri, Feb 15, 2013 at 5:49 PM, Oliver Urbann
> <oli...@tu...> wrote:
> > the process is migrated but the benchmark crashes with different
> > messages, e.g.:
> >
> > Client 3 aborted in state 11: FATAL:  semop(id=491526) failed:
> > Bezeichner wurde entfernt
> >
> > or
> >
> > Client 2 aborted in state 8: FEHLER:  lock RowExclusiveLock on object
> > 16384/16391/0 is already held
> >
> > Did anybody have success load balancing postgresql?
> > https://lists.sourceforge.net/lists/listinfo/ssic-linux-users
>
> IIRC, locks in OpenSSI is not system wide. Further more, when a
> process (the whole thread group in this case) migrated, then it is
> migrated entirely in the sense that it physically move.
>
> This is different than say MOSIX which use "stub" approach, so lock
> might still work because there is still communication between origin
> node and the new node (from the migration point of view)
>
> So that might explain the lock error message. To prove it, try to
> install MOSIX and see if the crash/error disappear during your test.
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>
>
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