[Pgpool-general] failback setup problem

[Uwe Bartels]

On 30 April 2011 11:42, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:

> >> > I have a different approach of recovering the postgres server. I'm
> >> > recovering from an existing backup. I do that because it is faster and
> I
> >> > don't put additional i/o load on the just activated server. I guess
> (or
> >> > hope) most people will have an existing backup.
> >> >
> >> > So my question is - if the aproach of recovering the failed server via
> a
> >> sql
> >> > command is optimal? What if both servers failed? then I'm not able to
> use
> >> > pcp-tools or pgpoolAdmin for recovering?
> >>
> >> I'm not sure what you are trying to do here. If "backup" means it was
> >> created by pg_dump_all, I don't think your approach works. Streaming
> >> replication requires a base backup(binary backup) which is managed by
> >> pg_start_backup/pg_stop_backup.
> >>
> >
> > Yes of course I have a backup created as described in
> >
> http://www.postgresql.org/docs/9.0/static/continuous-archiving.html#BACKUP-BASE-BACKUP
> > .
> >
> > My question is, what happens if both server failed somehow? Can I still
> use
> > pgpoolAdmin to recover a database server?
>
> No, pgpoolAdmin cannot recover a database server in this situation.
> You have to recover the database manualy.
>
Yes. I thought that of course.
So my question was, if you leave the whole restore process up to one called
recovery script - including optional checkpointing etc. pgpool would be more
flexible and simplier in terms of supporting different recovery procedures.

By he way - where does pgpool actually store the information about
attached/detached servers?

Best Regards,
Uwe




> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese: http://www.sraoss.co.jp
>
> > Best..
> > Uwe
> >
> >
> >
> >>
> >> > I'm asking because I worked for several years as an
> >> > it-production-responsible and I learned a little how administrators
> >> > think/work. They are happy if they have a (or better ONE) defined
> >> recovery
> >> > procedure.
> >> > Where am I getting? I'm asking you if it would makes sense to recode
> or
> >> > reduce the recovery procedure code to one system call e.g.
> >> failback_command.
> >> > Most people have their backup and restore functionality coded and
> ready
> >> for
> >> > training and/or desaster. If they could simply use this very same
> >> > functionality within pgpooladmin that would be great.
> >> >
> >> > It might be that i have overseen something (as before) and this is
> >> already
> >> > possible. If so please tell me how.
> >> >
> >> > Best Regards,
> >> > Uwe
> >> >
> >> >
> >> > On 26 April 2011 07:34, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> >> >
> >> >> > thanks, that message already helped. I tried to recover the
> postgres
> >> >> server
> >> >> > with the failback_command.
> >> >>
> >> >> You are welcome.
> >> >>
> >> >> > I didn't realize these recovery_* parameters yet.
> >> >> > So I use the recovery_* parameters for recovering the failed
> postgres
> >> >> > server.
> >> >>
> >> >> pgpool-II connects to backend to issue some SQLs including
> CHECKPOINT.
> >> >> recovery_* parameters define the user and password for the
> connection.
> >> >> Usually they are for PostgreSQL super user (postgres).
> >> >>
> >> >> > And the failback_command to attach the postgres server into pgpool
> >> >> > right?
> >> >>
> >> >> If you want to do something special, for example mailing to DBA, then
> >> >> you might want to specify it.  Otherwise you can leave it empty.
> >> >> --
> >> >> Tatsuo Ishii
> >> >> SRA OSS, Inc. Japan
> >> >> English: http://www.sraoss.co.jp/index_en.php
> >> >> Japanese: http://www.sraoss.co.jp
> >> >>
> >> >> > Best Regards,
> >> >> > Uwe
> >> >> >
> >> >> >
> >> >> > On 26 April 2011 01:06, Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> >> >> >
> >> >> >> > I'm using pg-pool-II 3.0.3 with streaming replication.
> >> >> >> > I coded the failback scenario/script for the slave server and
> the
> >> >> script
> >> >> >> > itself works fine.
> >> >> >> >
> >> >> >> > I now configured the failback script in pgpool.conf and during
> >> testing
> >> >> an
> >> >> >> > error message comes up:
> >> >> >> > 2011-04-09 06:42:18 LOG:   pid 16863: starting recovering node 1
> >> >> >> > 2011-04-09 06:42:18 ERROR: pid 16863: start_recover: could not
> >> connect
> >> >> >> > master node.
> >> >> >> >
> >> >> >> > [root at adt-web01 pgpool-II-3.0.3]# pcp_node_info 10 adt-web01
> 9898
> >> >> >> postgres
> >> >> >> > postgres 0
> >> >> >> > adt-db01 5432 1 0.500000
> >> >> >> > [root at adt-web01 pgpool-II-3.0.3]# pcp_node_info 10 adt-web01
> 9898
> >> >> >> postgres
> >> >> >> > postgres 1
> >> >> >> > adt-db02 5432 3 0.500000
> >> >> >> >
> >> >> >> > pcp commands and pgpooladmin report that the master is up and
> >> running
> >> >> and
> >> >> >> > I'm able to connect to the master directly and through pgpool.
> >> >> >> > So what's wrong? So far everything else works fine.
> >> >> >>
> >> >> >> Assuming you have set recovery_user and recovery_passwd correctly,
> >> I'm
> >> >> >> not sure what's going on. IMO, the error message is very rare.
> It's
> >> so
> >> >> >> rare and there's a bug in the error path, which had not been found
> >> for
> >> >> >> long time. Can please try attached patch? The patch add a little
> bit
> >> >> >> usefull info to the error message above.
> >> >> >> --
> >> >> >> Tatsuo Ishii
> >> >> >> SRA OSS, Inc. Japan
> >> >> >> English: http://www.sraoss.co.jp/index_en.php
> >> >> >> Japanese: http://www.sraoss.co.jp
> >> >> >>
> >> >>
> >>
>
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