[pgpool-general: 5192] Re: Architecture Questions

[Christophe Pettus]

> On Dec 21, 2016, at 14:12, Yates, James C. -ND <James.C.Yates.-ND at disney.com> wrote:
> 
> I would prefer to be in read only mode if the West/East link goes down. The App is opening two connections one for read and one for write.  The app will trap any write errors and continue.  The East Application Server will connect to the first East Database server that it can connect to and depend on PgPool to redirect any write traffic, The same with the West App Servers they would connect to the first West database server that it can connect to.  The idea is that we would not fail over across regions unless the entire region goes down.

There's no direct solution for this in pgpool; indeed, we generally recommend not using pgpool as the front end with one portion across a WAN link for precisely this reason.  For a pgpool instance on either side, there's no clean way of deciding if it is a "real" failure (the remote system went down) or a network partition, unless you handle all promotion manually... in which case, do you really need pgpool?

Multi-master replication (either the traditional way with Bucardo or the new evolving way with BDR) is a significantly better approach to this problem .

--
-- Christophe Pettus
   xof at thebuild.com