[Postgres-xc-general] Cluster restart

[Stefan L. <ar...@er...>]

Hello,

I'm new to the Postgres-XC project. In fact I am still considering if I 
should install it
in order to try it as a replacement of my current database clusters 
(those are based
around MySQL and its binary_log based replication). Before actually 
starting the
installation of postgres-xc I would like to know what is the procedure 
for restarting
nodes. I have already read a few documents/mails regarding restoring or 
resyncing
a failed datanode, however these documents does not answer my simple 
question:

What should be the procedure for rebooting servers? For example I have a 
kernel
updated pending (due to security reasons) - I'm installing the new 
kernel, but I have
to reboot all machine. Theoretically all nodes (both coordinators and 
datanodes)
are working on different physical servers or VMes. In a perfect scenario 
I would
like to keep the system in production while I am restarting the servers 
one by one.
However I am not sure what would be the effect of rebooting servers one 
by one.

For purpose of example let me have four datanodes: A,B,C,D

All servers are synced and are operating as expected.
1) Upgrade A, reboot A
2) INSERT/UPDATE/DELETE queries
3) A boots up and is successfully started
4) INSERT/UPDATE/DELETE queries
5) Upgrade B, reboot B
...
...

As for the "Coordinators" nodes. How are those affected by temporary 
stopping
and restarting the postgres-xc related services. What should be the load 
balancer
in front of these servers in order to be able to both load-balance and 
fail-over if
one of the Coordinators is offline either due to failed server or due to 
rebooting
servers.

I have no problem with relatively heavy operation of full restore of a 
datanode in
event of failed server. Such restoration operation can be properly 
scheduled and
executed, however I am interested how would postgres-xc react to simple
scenarioa simple operation of restarting a server due to whatever
reasons should

Kind Regards,
Stefan Lekov