Re: BUG #5465: dblink TCP connection hangs blocking translation from being terminated

On May 19, 8:41=A0pm, m...@joeconway.com (Joseph Conway) wrote:
> Magnus Hagander wrote:
> > On Wed, May 19, 2010 at 5:10 AM, Valentine Gogichashvili
> > <val...@gmail.com> wrote:
> >> The following bug has been logged online:
>
> >> Bug reference: =A0 =A0 =A05465
> >> Logged by: =A0 =A0 =A0 =A0 =A0Valentine Gogichashvili
> >> Email address: =A0 =A0 =A0val...@gmail.com
> >> PostgreSQL version: 8.2.1
> >> Operating system: =A0 Red Hat 3.4.6-3 (kernel 2.6.9-42.0.3.ELsmp)
> >> Description: =A0 =A0 =A0 =A0dblink TCP connection hangs blocking trans=
lation from
> >> being terminated
> >> Details:
>
> >> Hi all,
>
> >> we have an issue on our productive server. A stored procedure, that us=
es
> >> dblink to get some data from the remote database hangs not responding =
to
> >> kill signal and holds several locks on some tables as well as an advis=
ory
> >> lock. So I have this transaction to be completed in order to have a
> >> possibility to operate the database normally.
>
> > I believe this is a known issue in dblink, where it's not possible to
> > cancel it when it's waiting in the TCP layer in the kernel.
> > Unfortunately, there is no fix ATM - there was some work towards it
> > for 9.0 at one point, but I think this is actually the first real
> > bug-report on the issue...
>
> I thought the known issue was only on Windows though...
> Note that this is not dblink specific but rather libpq.
>
> >> How would it be possible to shutdown the DB in case this session proce=
ss is
> >> not responding to normal kill signals? Will it hinder the database from
> >> shutting down normally? My previous experience with issuing immediate =
stops
> >> or killing with -9 had been quite catastrophic and I could not start t=
he DB
> >> afterwards. What would you suggest in this case?
>
> > kill -9 on a client will make the postmaster restart the whole
> > process, so yes, it's a very heavy operation.
>
> Can you grab the process with gdb and call elog() manually?
>
> Joe
>
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Unfortunately I could not install gdb on that machine :-( some
dependencies are not installable and I cannot upgrade that production
machine...

-- Valentine