[Zope] Strangeness with Zope and Postgres

[Lutz Steinborn]

We have this problem also.
We are using popy 2.0.7 with postgres 7.1.3.
Where is no newer stable version available at the moment.
Regards

Lutz Steinborn


On Fri, 2 Nov 2001 11:1

3:37 +0100
Christian Theune <ct@gocept.com> wrote:

> Hi.
>=20
> We had this problem too. The thing is with PoPy.
> I think this is solved in a newer version of PoPy.
>=20
> Please mail me again if a newer version won't help,
> then i have to take a look how we solved this,
> but we did, so go on and ask me.
>=20
> Christian
>=20
> On Thu, Nov 01, 2001 at 04:43:10PM -0500, Chris Kratz wrote:
> > For months now, we have been noticing that every once in awhile
zope just
> > appears to freeze up.  I go and look at the zope processes and
they are all
> > sleeping.  The only way to fix the problem was to restart zope,
hence I
> > didn't think about the fact that it might be the database.  I have
been
> > monitoring it and assumed it was something funny in Zope, but
something that
> > was mentioned on this list made me start thinking that it could be
something
> > funny happening with the database.
> >=20
> > We use postgres as our dbms and our site is heavily database
instensive.
> > Sure enough, when ever the site appears to freeze, I go and look
at the
> > database threads and one thread has a status of "UPDATE WAITING"
and the the
> > others are sitting in the normal idle in transaction status.  The
server is
> > idle (2% or less cpu) and the drives are as normal, silent.  The
server is
> > doing absolutely nothing.
> >=20
> > I also found out how to lock it up every time.  I have a specific
page that
> > does some intensive database work including some updates to some
preference
> > tables as well as some reads of some large tables, etc.  If I go
to that
> > page and then hit F5 twice in succession, it locks up the system
every time
> > requiring a zope restart.
> >=20
> > Now I am starting to think that we are running into a concurrency
issue with
> > postgres and transactions.  I was wondering if anyone with a bit
more
> > experience might be able to shed some more light on the situation
and/or
> > where I might look to further debug the situation.
> >=20
> > My hunch is that the following happens:
> > 1. First request comes in.
> > 2. User presses F5 before the first transaction finished.
> > 3. Browser drops first connection and reconnects.
> > 4. Zope starts to write to the socket, notices that the browser is
no longer
> > connected.
> > 5. Zope aborts the transaction.
> > 6. BUT, the database never get's a rollback and simply waits in
the
> > transaction for ever.
> > 7. Unfortunately, this must also cause some locks that don't allow
any other
> > thread to do any work.
> > 8.  Restarting Zope closes those db connections and postgres roles
the
> > transaction back.
> >=20
> > Does anyone have any further suggestions on how to debug this
further or to
> > stop the problem?
> >=20
> > -Chris
> >=20
> > RH 7.2
> > Zope 2.4.1
> > ZPoPyDA
> > Postgres 7.1.3
> > ------------------------------
> > Chris Kratz
> > chris.kratz@vistashare.com
> >=20
> >=20
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>=20
> --=20
> Christian Theune - ct@gocept.com
> gocept gmbh & co.kg - schalaunische strasse 6 - 06366 koethen/anhalt
> tel.+49 3496 3099112 - fax.+49 3496 3099118 mob. - 0178 48 33 981
>=20
> reduce(lambda x,y:x+y,[chr(ord(x)^42) for x in 'zS^BED\nX_FOY\x0b'])
>=20
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--=20
Lutz Steinborn                   mailto:l.steinborn@4c-ag.de
4c AG                            Tel +49 6092 999592
Stefan-George-Ring 22-24         Fax +49 89 99341 399
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