[pgpool-general: 5191] Re: Architecture Questions

Yates, James C. -ND James.C.Yates.-ND at disney.com
Thu Dec 22 07:12:13 JST 2016

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.

On Dec 21, 2016, at 1:56 PM, Muhammad Usama <m.usama at gmail.com<mailto:m.usama at gmail.com>> wrote:

On Tue, Dec 20, 2016 at 10:24 PM, Yates, James C. -ND <James.C.Yates.-ND at disney.com<mailto:James.C.Yates.-ND at disney.com>> wrote:
What I’m concerned about is the corporate network link between the AWS regions going down and PgPool doing a failover.  Then I could have the East and West region both think they have a master and doing updates/inserts on each.  Then when the link comes back up, my databases are out of sync and I could lose data.

Yes, This is a valid point. Earlier I thought you were concerned about the Watchdog going into the split-brain which is not likely to happen especially in the active-active watchdog configurations.
Unfortunately, I can't think of any perfect solution for backend failover in case of a network partitioning between East and West regions at the moment, Can you please explain the availability requirements of your application, Like when the regions are isolated from each other, is it okay as per the requirements that the region that does not have the primary PostgreSQL keeps offline until the link is restored?

Muhammad Usama

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