Re: Locking question?

From: Jim Nasby <decibel(at)decibel(dot)org>
To: Shoaib Mir <shoaibmir(at)gmail(dot)com>
Cc: "Gurjeet Singh" <singh(dot)gurjeet(at)gmail(dot)com>, PostgreSQL <pgsql-general(at)postgresql(dot)org>
Subject: Re: Locking question?
Date: 2007-02-07 04:13:46
Message-ID: 215B989A-A534-4345-A863-B9FF637B02E5@decibel.org
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Well... if the application crashes then normally the TCP connection
would drop as well.

The problem is that in many environments it can take a *long* time
for the backend to realize that the client went away. The
tcp_keepalives_* settings are intended to try and reduce that time to
a more reasonable value, but bear in mind that they depend on the TCP
stack provided by the OS/environment, so it's not guaranteed to work
perfectly.

On Feb 6, 2007, at 3:21 AM, Shoaib Mir wrote:

> There is such timeout from the database server for the idle
> connections but yes you can always use firewall settings in order
> to do that and kill idle connections.
>
> --
> Shoaib Mir
> EnterpriseDB ( www.enterprisedb.com)
>
> On 2/6/07, Gurjeet Singh <singh(dot)gurjeet(at)gmail(dot)com> wrote: On
> 1/30/07, Alvaro Herrera <alvherre(at)commandprompt(dot)com> wrote:
> Shoaib Mir wrote:
> > While debugging an application, I just wanted to confirm from the
> list here:
> >
> > Suppose I have a long running transaction which has a few updates
> and
> > inserts running on some specific tables which means it has acquired
> > Exclusive locks too during the transaction on specific table but
> if just
> > before commit the client app crashes and the commit is never
> sent, will the
> > Exclusive locks be automatically released?
>
> Yes (assuming the backend dies in the process, which may not
> happen if
> the app dies silently and while not waiting for anything from the
> server).
>
>
> Do you mean that the Ex-lock will be held indefinitely in the
> following situation"
>
> i) Appln. acquires Exclusive lock.
> ii) Appln. sleeps or is interacting with human.
> ii) Appln. crashes.
>
> Doesn't the backend kill itself if it detects that the other side
> of the communincation channel has gone down?
>
>
> --
> gurjeet[(dot)singh](at)EnterpriseDB(dot)com
> singh(dot)gurjeet(at){ gmail | hotmail | yahoo }.com
>

--
Jim Nasby jim(at)nasby(dot)net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)

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