[pgpool-general: 8890] Re: DB Connection ERROR during a failover

[Bo Peng]

Hi,

Sorry for the late reply.

> My questions are:
> 
> 1. Is *failover.sh *executed everytime any node goes down?

If pgpool detects the node down and triggers a failover,
the script specified in failover_command will be executed.

failover.sh is the script which you specified in failover_command.
You can customize this script.

> 2. When such a *failover *event is triggered, what happens to all the
> connections opened against all the nodes?

If the DOWN node is standby and is not load balacing node,
the existing session may not be affected in some cases.

On Thu, 6 Jul 2023 19:51:28 +0530
Gopikrishnan <nksgopikrishnan at gmail.com> wrote:

> Hi all,
> 
> Any info. would be much appreciated.
> My questions are:
> 
> 1. Is *failover.sh *executed everytime any node goes down?
> 2. When such a *failover *event is triggered, what happens to all the
> connections opened against all the nodes?
> 
> *Thanks*
> *Gopi*
> 
> 
> On Thu, Jun 29, 2023 at 2:04 PM Gopikrishnan <nksgopikrishnan at gmail.com>
> wrote:
> 
> > Hi Bo, all,
> >
> > Thank you for your responses.
> > Can you please confirm under what conditions the failover.sh script is
> > executed? (Even though the script will be skipped if the node failing is
> > non-primary)
> >
> > 1. Is it executed every time when a node is down?
> > (Because during this time, I am expecting the DB connection attempt will
> > not work since failover is being executed)
> >
> > 2. Also, in this state (Executing failover) what happens to the existing
> > DB connections that were opened before failover event)
> >
> > Thanks again for your help,
> > Gopi
> >
> > On Fri, 23 Jun, 2023, 5:34 am Bo Peng, <pengbo at sraoss.co.jp> wrote:
> >
> >> Hi,
> >>
> >> Sorry for the late reply.
> >>
> >> > Thanks for your response. To avoid hitting this error,
> >> > Is there a way to skip executing this failover since it is not the
> >> primary
> >> > node that failed?
> >>
> >> Unfortunately, there is currently no workaround.
> >>
> >> > I am using pgpool 4.0.4, Is this scenario enhanced in any later
> >> versions?
> >>
> >> Yes. We have plan to enhance this feature.
> >>
> >> > On Wed, Jun 14, 2023 at 9:34 AM Bo Peng <pengbo at sraoss.co.jp> wrote:
> >> >
> >> > > Hi,
> >> > >
> >> > > > In my application, I see an error:
> >> > > >
> >> > > > Caused by: org.postgresql.util.PSQLException: FATAL: failed to
> >> create a
> >> > > > backend connection
> >> > > >   Detail: executing failover on backend
> >> > > > at
> >> > > >
> >> > >
> >> org.postgresql.core.v3.ConnectionFactoryImpl.doAuthentication(ConnectionFactoryImpl.java:514)
> >> > > > at
> >> > > >
> >> > >
> >> org.postgresql.core.v3.ConnectionFactoryImpl.tryConnect(ConnectionFactoryImpl.java:141)
> >> > > > at
> >> > > >
> >> > >
> >> org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:192)
> >> > > >
> >> > > > Is there a configuration I can use to make the connection wait for
> >> the
> >> > > > failover to complete?
> >> > >
> >> > > Unfortunately, pgpool doesn't have such feature.
> >> > > You need to add such retry logic in your application code.
> >> > >
> >> > > > Also, I can see that the failover was not indeed a failover, i.e the
> >> > > > failover would eventually
> >> > > > be skipped since it is not the primary node that failed:
> >> > > >
> >> > > > 2023-06-12_18:27:55 [failover.sh]: failed_node_id=1
> >> > > failed_host=10.198.49.42
> >> > > > 2023-06-12_18:27:55 [failover.sh]: old_master_node_id=0
> >> > > > old_primary_node_id=0
> >> > > > 2023-06-12_18:27:55 [failover.sh]: new_primary_node_id=0
> >> > > > new_master_host=10.198.49.41
> >> > > > 2023-06-12_18:27:55 [failover.sh]: Node 1 dies, but it's not the
> >> primary
> >> > > > node. Skipping failover.
> >> > >
> >> > > Yes. Pgpool-II checks the role of the failed node in the failover
> >> script.
> >> > > If the failed node is a standby node, pgpool just updates
> >> > > the node status to DOWN and skips failover.
> >> > >
> >> > > --
> >> > > Bo Peng <pengbo at sraoss.co.jp>
> >> > > SRA OSS LLC
> >> > > TEL: 03-5979-2701 FAX: 03-5979-2702
> >> > > URL: https://www.sraoss.co.jp/
> >> > >
> >>
> >>
> >> --
> >> Bo Peng <pengbo at sraoss.co.jp>
> >> SRA OSS LLC
> >> TEL: 03-5979-2701 FAX: 03-5979-2702
> >> URL: https://www.sraoss.co.jp/
> >>
> >


-- 
Bo Peng <pengbo at sraoss.co.jp>
SRA OSS LLC
TEL: 03-5979-2701 FAX: 03-5979-2702
URL: https://www.sraoss.co.jp/