Re: keep alive and running query

From: Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>
To: "desmodemone *EXTERN*" <desmodemone(at)gmail(dot)com>, "pgsql-admin(at)postgresql(dot)org" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: keep alive and running query
Date: 2013-12-16 09:31:48
Message-ID: A737B7A37273E048B164557ADEF4A58B17C839D2@ntex2010i.host.magwien.gv.at
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desmodemone wrote:
> As I tested and saw until now, the keep alive functions as follow [if I understand correctly and it's
> not a bug] :
>
> When a connection it's in idle state or in idle in transaction, if the connection with client it's
> broken for a number of keep alive, the backend will be terminated.
>
>
> By the way if this could be ok in an OLTP enviroment, because the average time of a query is << the
> time of keep alive, in a DWH enviroment could be a problem.
>
> Imagine your application server, where there is an ETL, will go down for 1 minute and your
> transactions are still running on the DWH database, that transactions could run for hours before the
>
> keep alive will terminate them, because they are in transaction state and not idle or idle in
> transaction.

TCP keepalive will also terminate a session that is currently
stuck in a long running SQL query if the client end dies.

I think that your problem is that you mix up different meanings of "idle".

In PostgreSQL, a connection is idle (or idle in transaction) if processing
of the last command is finished and the server is waiting for the next
command from the client.

In TCP, a connection is idle if there is no network traffic.

Yours,
Laurenz Albe

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