[pgpool-general: 1443] Re: removing nodes from pgpool without restarting

Michael Betts mbetts at softdevgroup.com
Thu Feb 28 10:52:53 JST 2013


Thank you for the explanation. I was thinking of failover as the just the primary node failing;
it now makes sense to me that it is any node failing.

I am trying to have autoscaling with no down time, so it would be nice to have
reload also remove nodes with status 3 that are no longer in pgpool.conf. 

Thanks again,


On Feb 27, 2013, at 7:22 PM, Tatsuo Ishii wrote:

>> Hi,
>> I have set up pgpool 3.2.3 in master/slave mode with streaming replication and it works fine.  Now I want to use autoscaling to add and remove nodes as demand fluctuates. Scaling up works with no problems, but when I scale down, I want to remove the extra nodes from pgpool wiithout restarting.  What happens now is I call pcp_detach_node(), which changes the status from 2 to 3 for that node, but leaves it in the pool.  I also remove the backend from the config file and reload it, but that has no effect unless you restart pgpool.
>> 1. Is there a way to just remove a node from pgpool?
> No(without restarting pgpool).
>> 2. If not, is it a problem to leave a number of nodes with status 3 in the pool?  The nodes themselves will have been terminated.
> Should be no problem. Leaving those unused nodes in pgpool.conf will
> cause problem when you restart pgpool though (they will trigger
> immediate failover).
>> 3. I see that when I detach a standby node, it calls the failover command - why?
> Pgpool-II handles the failover event in uniform way. In fact the
> difference between failover and detach is just the former is triggered
> by detection of errors, while the latter is triggered by pcp command.
> --
> 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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