[pgpool-general: 665] Re: Explanation of promote button in pgpooladmin interface

[Tatsuo Ishii]

>> "promote" button just executes pcp_promote command.
> 
> 
> And this is not available in PgPool 3.0.x? Only 3.1.x?

It's only available in 3.1.x.

>> If you want to
>> change the primary node from Ubuntu2 to Ubuntu1, please follow step:
>>
>> 1) Shutdown Ubuntu2.
>>
>> 2) Ubuntu1 should automatically take over and become primary.
>>
>> 3) At this point you should find "Recovery" button at Ubuntu2
>>   row. Press the "Recovery" button to make Ubuntu2 as new standby
>>   server.
>>
> 
> Thanks- but if I upgrade, will "promote" allow me to change Primary servers
> without stopping the existing primary- is that what it is supposed to do?

No. 

pcp_promote_node does following:

1) Tell pgpool which should be the new primary,
2) Pgpool waits until all clients get disconnected.
3) Pgpool does fail over to update status information(regarding which
   one is the primary) of each pgpool child process.

BTW with PostgreSQL streaming replication it is possible that the
standby promotes to the primary without stopping the standby.  However
it is *not* possible to demote the primary to standby without
restarting it.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp