[pgpool-general: 2557] Re: Preventing split-brain

Josh Berkus josh at agliodbs.com
Tue Feb 11 07:13:24 JST 2014

On 02/10/2014 06:17 AM, Theron Luhn wrote:
> Virtual IP, I believe, is supposed to help with problem, by allowing for
> only a single PgPool master.  However, this isn't an available option.  I
> could emulate VIP by updating the configuration of the clients to point to
> the new PgPool.  However, this would be fruitless:  If PgPool B can't
> communicate with PgPool A, it very well may not be able to communicate with
> a client in the same datacenter as PgPool A.
> This seems like a very difficult problem to solve, but it cannot be an
> uncommon one.  Can anybody share some insight?

FWIW, I'm doing a talk about this at NYC PgDay.

The short of it is that there is no way to solve your problem in a
two-datacenter system where you're trying to cope with datacenter
failure and network outages.  In order to make this work, you must have
some kind of tiebreaker resource (hosted in neither datacenter), which
can decide which side of a network split "wins".  Ideally, you can set
up that tiebreaker resource so that it only gets checked when there's a
failure event; that way the tiebreaker does not itself become a SPOF.

Josh Berkus
PostgreSQL Experts Inc.

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