[Postgres-xc-developers] gtm output and other gtm issues yet.

[Koichi S. <ko...@in...>]

Thanks.   I tested the patch both on master and REL1_0_STABLE and found they look to work fine.  I will commit it to both branches.

I found there are two more issues on GTM.

1) If we kill GTM process, GTM will begin to assing GXID values with the one of the proveious GTM run.  It is bad and harmful behaviour.   To improve it, GTM should write the next gxid value to gtm.control.   When gxid value reaches this backup, then the backup should be refreshed with the new one.   That way, we can safely restart GTM even if it was killed.   When GTM stops normally, it should write the next gxid value to gtm.control.

2) We have BARRIER to synchronize PITR recovery line.   However, GTM does not have this capability.  In this case, GTM's sequence definition could be inconsisitent if ALTER SEQUENCE or DROP SEQUENCE was issued after the recovery point.   Have WAL in GTM could be a general choice but it seems to be too much for current GTM feature.  Instead, we can have GTM.control backups when CREATE BARRIER is issued.   Backup files will be qualified by BARRIER id so that DBA can choose which backup to use at the end of PITR.

Regards;
---
Koichi

On Sun, 17 Feb 2013 10:27:37 +0530
Nikhil Sontakke <ni...@st...> wrote:

> Hi Suzuki-san,
> 
> > It's so helpful to have this patch.   Will review and test it before committing.
> >
> 
> Any comments on this patch? I do not see it in the commit logs.
> 
> Regards,
> Nikhils
> 
> > Best;
> > ---
> > Koichi Suzuki
> >
> > On Wed, 6 Feb 2013 14:25:48 +0530
> > Nikhil Sontakke <ni...@st...> wrote:
> >
> >> > Also, gtm_ctl -w option
> >> > seems not work properly.
> >> >
> >>
> >> PFA, a patch to fix "gtm_ctl -w" behavior in GIT HEAD. I also tested
> >> "-w -t nsecs" behavior and it seems to work as well. This patch can be
> >> easily be backported to 1.0 if desired. I hope all these obnoxious gtm
> >> startup issues are resolved now. Scripting was a bit painful because
> >> of these issues.
> >>
> >> Regards,
> >> Nikhils
> >>
> >> > I will take a look at these issue and fix at least in the next major
> >> > release.    Daemonization should be back-ported to 1.0.x.
> >> >
> >> > Kind Regards;
> >> > ----------
> >> > Koichi Suzuki
> >> >
> >> >
> >> > 2012/12/27 Michael Meskes <me...@po...>:
> >> >> I still haven't found the time to dig into this, but could anyone please
> >> >> explain to me how gtm is supposed to start up? A simple grep command doesn't
> >> >> seem to find any call to setsid() in gtm subdirs. Could you please point me to
> >> >> the code where gtm daemonizes? Because if it doesn't correctly, there is no
> >> >> suprise gtm_ctl doesn't come back. Or in other words, this is a logical point
> >> >> to start looking.
> >> >>
> >> >> Michael
> >> >> --
> >> >> Michael Meskes
> >> >> Michael at Fam-Meskes dot De, Michael at Meskes dot (De|Com|Net|Org)
> >> >> Michael at BorussiaFan dot De, Meskes at (Debian|Postgresql) dot Org
> >> >> Jabber: michael.meskes at gmail dot com
> >> >> VfL Borussia! Força Barça! Go SF 49ers! Use Debian GNU/Linux, PostgreSQL
> >> >>
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