Re: [Postgres-xc-general] Synchronous multimaster

On Thu, Dec 22, 2011 at 7:14 PM, peppux <pe...@gm...> wrote:

> Hello guys,
> i've two remote servers with postgres.
>
> I'd like to configure them so that when changing one, automatically
> changes the other database.
> I think that i need to configure them as sync multimaster.
>
> Someone can help me please?
> Thanks in advice.
>
As said before, this is an extremely difficult implementation, and you have
to think about a lot of corner cases.
Regarding your application, I would define your application as a 1-layer
multimaster.
Each node is a master, contains the data, and can run independently in case
it is unique.
The main difference we have in Postgres-XC is that we use a 2-layer master
with datanode and Coordinator.
On the top of that, XC uses GTM to feed global transaction ID, snapshot and
sequence values to other nodes.

In the case of 1 layer though, I think you may be able to implement
transaction ID feed, snapshot and snapshot value directly from one of the
nodes, by using a new type of mechanism, what has not been designed yet
though. To give you an idea if you wish to work on that, multimaster
replication will need to have a consistent mechanism to send WAL among all
the nodes to keep data consistency...
But that's pretty complicated.
-- 
Michael Paquier
http://michael.otacoo.com