[pgpool-general: 8857] Re: DB Connection ERROR during a failover

[Gopikrishnan]

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/
>
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