[pgpool-general: 3232] Postgres, Pgpool2 for Autoscaling in private cloud (OpenStack)

[Job Cespedes]

Hi,

I'm currently researching on HA, Failover, Autosacaling applications in
private clouds.  I consider Pgpool2 and Postgres a viable option for the DB
layer. But I have several question about whether to use horizontal or
vertical scaling. So far I think vertical scaling would be the way to go
for the DB layer. Adding more nodes in a master/slave configuration doesn’t
seem right performance-wise and it seems more complex also. Besides I think
could only add more slaves nodes. But maybe someone out there knows better.


Anyway my question is the following:


The promotion of a slave to master is transparent for the client connected
to pgpool or there’s a short connection loss (data loss)?


The scenario I have in mind is: for vertical scaling I could start by
shutting down a slave node, provisioning more resources, boot again, and
promote to master with the command pcp_promote_node, after that I could do
the same with the former master, now slave, and then do an online recovery.
However, I’m not sure this is completely transparent for clients and
whether or not it has zero downtime.


Thanks for any piece of advice,


-- 
Job Cespedes
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