[Pgpool-general] Error message when sending query that causes failover

[Tatsuo Ishii]

In summary it's an expected behavior. You saw that when second node
went down, the session was not disconncted is a bug with 2.1. In the
CVS head you will see the same behavior regardless which node goes
down.

The reason for this change was explained in the following thread:

http://lists.pgfoundry.org/pipermail/pgpool-general/2008-July/001119.html
--
Tatsuo Ishii
SRA OSS, Inc. Japan

> Hello everyone!
> 
> I have two instances of PostgreSQL running behind pgpool-II 2.1 with
> connection pooling, replication and load balancing. Online recovery is
> working fine with PITR. Now I have this situation:
> 
> - I send an UPDATE statement to the cluster and it goes fine.
> - I shutdown PostgreSQL on the master node.
> - I send another UPDATE statement to the cluster (before the health
> check happens) and pgpool-II detects the master node is down, therefore
> it returns an error and does not execute the SQL statement. It does the
> failover correctly, though.
> - I send the same UPDATE again and it works fine (on the remaining node
> only, of course).
> 
> What I was expecting is that, when I send the UPDATE statement and
> pgpool-II realises it is unable to contact the node, it would do
> failover AND execute the statement on the remaining node. And return an
> OK to the client.
> 
> Here you are some code, made on the classic table structure of pgbench:
> 
> $ psql -h 10.0.33.252 -p 9999 -U pgpool2 -d bench_replication -c "UPDATE
> ACCOUNTS SET abalance = 1011 WHERE aid = 10"
> UPDATE 1
> "/etc/init.d/postgresql stop" on master node
> $ psql -h 10.0.33.252 -p 9999 -U pgpool2 -d bench_replication -c "UPDATE
> ACCOUNTS SET abalance = 1012 WHERE aid = 10"
> psql: server closed the connection unexpectedly
> 	This probably means the server terminated abnormally
> 	before or while processing the request.
> $ psql -h 10.0.33.252 -p 9999 -U pgpool2 -d bench_replication -c "SELECT
> abalance FROM ACCOUNTS WHERE aid = 10"
>  abalance
> ----------
>      1011
> (1 row)
> 
> This does not happen if I shutdown the slave node, only the master.
> 
> Is this the expected behaviour? Is there any way to change it?
> 
> Thanks in advance.
> 
> --
> Jaume Sabater
> http://linuxsilo.net/
> 
> "Ubi sapientas ibi libertas"
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