Re: transaction idle timeout in 7.4.5 and 8.0.0beta2

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Jeroen T(dot) Vermeulen" <jtv(at)xs4all(dot)nl>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: transaction idle timeout in 7.4.5 and 8.0.0beta2
Date: 2004-09-18 20:05:26
Message-ID: 7412.1095537926@sss.pgh.pa.us
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"Jeroen T. Vermeulen" <jtv(at)xs4all(dot)nl> writes:
> On Sat, Sep 18, 2004 at 02:32:32PM -0400, Tom Lane wrote:
>> If there's a communications
>> problem, it might take awhile to detect connection loss ... but if
>> there's a communications problem, you probably aren't going to be able
>> to open a new connection, either.

> Unfortunately, a communications problem is exactly the kind of scenario
> we were talking about in the first place! Might be a misguided firewall,
> for instance. (In which case we'd want the TCP connection to time out
> quickly on the server as well to avoid piling up dead backends, but that's
> another matter).

Well, I think it would time out quickly --- anyway on the order of
minutes not hours. By hypothesis, the situation you're worried about is
where the backend was unable to send you a COMMIT acknowledgement
message. The kernel is going to realize that it didn't get an ACK back,
and is going to retry a few times, and is then going to declare the
connection lost. The case where you may have a very long delay before
detection of connection loss is where the backend is sitting idle with
nothing to send.

regards, tom lane

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