[pgpool-general: 3060] Re: PGPool connection dropped when using pg_detach

[James Sewell]

Hey,

So there is no way of manually taking a postgresql node out of a pool
without interrupting traffic to all other postgresql nodes?

Cheers,


James Sewell,
PostgreSQL Team Lead / Solutions Architect
______________________________________


 Level 2, 50 Queen St, Melbourne VIC 3000

*P *(+61) 3 8370 8000  *W* www.lisasoft.com  *F *(+61) 3 8370 8099



On Fri, Jul 25, 2014 at 3:07 PM, Tatsuo Ishii <ishii at postgresql.org> wrote:

> I cannot imagine how you maintenance the database while a user
> connects to the database:-)
>
> BTW I'm not sure if this is usefull for you or not,
> but... pcp_detach_node accepts -g option which force pcp_detach_node
> wait until all clients exit.
>
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
>
> > Cool,
> >
> > Thanks Tatsuo.
> >
> > Is there a way of taking a postgresql node out of a pool without causing
> > connections to other postgresql nodes to drop?
> >
> > This would be used in a situation such as database maintenance.
> >
> > Cheers,
> >
> >
> > James Sewell,
> > PostgreSQL Team Lead / Solutions Architect
> > ______________________________________
> >
> >
> >  Level 2, 50 Queen St, Melbourne VIC 3000
> >
> > *P *(+61) 3 8370 8000  *W* www.lisasoft.com  *F *(+61) 3 8370 8099
> >
> >
> >
> > On Fri, Jul 25, 2014 at 2:43 PM, Tatsuo Ishii <ishii at postgresql.org>
> wrote:
> >
> >> > Hey all,
> >> >
> >> > This is a seemingly a pretty bad problem which I uncovered as part of
> my
> >> > last post, so the start of the message will be similar.
> >> >
> >> > I have two pgpool nodes which I am using a TCP load balancer to spread
> >> > between. I am using watchdog to synchronise PostgreSQL node
> information
> >> > between the two and an external HA solution (with ALLOW_TO_FAILOVER).
> >> >
> >> > If I start both my pgpool nodes up I get the following initial state:
> >> >
> >> > postgres=# show pool_nodes;
> >> >  node_id |  hostname   | port | status | lb_weight |  role
> >> > ---------+-------------+------+--------+-----------+---------
> >> >  0       | 10.10.10.1   | 5432 | 2      | 0.500000  | standby
> >> >  1       | 10.10.10.2   | 5432 | 2      | 0.500000  | primary
> >> > (2 rows)
> >> >
> >> > Now I open a PSQL connection and do the following:
> >> >
> >> > postgres=# SELECT inet_server_addr();
> >> >  inet_server_addr
> >> > ------------------
> >> >  10.10.10.2
> >> > (1 row)
> >> >
> >> > This shows I am connected to the primary.
> >> >
> >> > I can run this multiple times and I will always be connected to the
> >> > primary, as long as I don't close the psql session.
> >> >
> >> > Then from another window I run the following command:
> >> >
> >> >  pcp_detach_node 1 load_balancer 9898 postgres postgres 0
> >> >
> >> > And in the same PSQL session run the command again:
> >> >
> >> > postgres=# SELECT inet_server_addr();
> >> > SSL SYSCALL error: EOF detected
> >> > The connection to the server was lost. Attempting reset: Succeeded.
> >> >
> >> > This is strange. Why has my master connection been severed?
> >>
> >> It's an expected behavior of pcp_detach_node, which causes failover
> >> and all existing sessions are disconnected.
> >>
> >> Best regards,
> >> --
> >> 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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