[Fwd: Re: misc/72498: Libc timestamp code on jailed SMP machine generates incorrect results]

Hi guys,

Following up on the bug I posted the other day about incorrect
timestamps, the FreeBSD team are wondering if it might be caused by
conflicting PostgreSQL instances in different FreeBSD jails on the same
host machine.

However, we've noticed no other problems with this configuration over
the last several and I was under the impression this is a fairly common
scenario.

Is anyone able to verify or deny that PostgreSQL instances in different
jails (each with their own IP address) will not corrupt each other? I'm
aware they allocate shared memory from a "global pool" of it as made
available on the host system, but have been under the impression
PostgreSQL is coded to not corrupt in this kind of situation.

Regards and best wishes,

Justin Clift

-------- Original Message --------
Subject: Re: misc/72498: Libc timestamp code on jailed SMP machine
generates incorrect results
Date: Mon, 11 Oct 2004 09:33:38 +0200
From: Uwe Doering <gemini(at)geminix(dot)org>
Organization: Private UNIX Site
To: Justin Clift <jc(at)telstra(dot)net>
CC: freebsd-gnats-submit(at)FreeBSD(dot)org
References: <200410110202(dot)i9B228Ye060291(at)www(dot)freebsd(dot)org>

Justin Clift wrote:
>
>>Environment:
>
> FreeBSD was-dev.telstra.net 4.10-RELEASE FreeBSD 4.10-RELEASE #0: Fri Jun 25 14:23:42 EST 2004 root(at)verdelho(dot)telstra(dot)net:/usr/src/sys/compile/1GB_SHARED_V3 i386
>
>>Description:
>
> We're using PostgreSQL 7.4.5 in an SMP jailed environment on FreeBSD 4.10.
>
> Inside this jail PostgreSQL is configured to output timestamp information in it's log file entries. There appears to be a bug in the timestamp generation code, as for hours above 9 oclock (10am and onwards) the timestamp's being generated are occasionally incorrect:
> [...]

Do you happen to run more than one instance of PostgreSQL on that
machine, each in its own jail? If so, are you aware that jails don't
have separate SysV shared resources (memory regions etc.), at least not
in FreeBSD's original 4.x implementation? In this scenario your problem
might be caused by clashing PostgreSQL instances, and you're likely to
be in for more serious problems than just time stamp corruption.

Just an educated guess, of course.

Uwe
--
Uwe Doering | EscapeBox - Managed On-Demand UNIX Servers
gemini(at)geminix(dot)org | http://www.escapebox.net