Date: Mon, 22 Sep 2008 17:06:34 +0200
From: Tino Schwarze <postgresql@tisc.de>
To: pgsql-admin@postgresql.org
Subject: Re: SIGKILL and force disconnecting user sessions
Message-ID: <20080922150634.GE10876@easy2.in-chemnitz.de>
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On Mon, Sep 22, 2008 at 09:43:29AM -0400, Brian A. Seklecki wrote:

BTW: What version of PG are you using?

> We need to kill apache P-conn pools from a an application/web server
> cluster for a specific database.  We use a load-balancer, so we shut
> down the HA L4 Service VIP that the web servers pconnect() to, to
> prevent new incoming connections.
> 
> The problem is then net.inet.tcp.* timeouts.  We need to cane existing
> connections with a quickness, and pg_stat_activity is a read-only view.
> 
> We need to kill the stale pcons, so just:
>  $ pkill -a [database string]
> 
>  The connection goes away as "Disconnected per admin command"
> 
>  I just want to confirm:
> 
>  1) There are no data consistency threats to SIGKIL a child thread
>     process?  Transactions and locks will be handled gracefully?

As far, as you do not really use SIGKILL (9), but SIGTERM (15),
everything should be fine.

>  2) There are no pgsql/admin level CLI builtin commands to do this in a
>     more graceful manor?

You might want to try pg_cancel_backend(pid) to cancel backends,
but I suppose, the connection will stay alive.
- see http://www.postgresql.org/docs/8.2/static/functions-admin.html

HTH,

Tino.

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