Subject: Re: Sync Rep Design
From: Simon Riggs <simon@2ndQuadrant.com>
To: Stefan Kaltenbrunner <stefan@kaltenbrunner.cc>
Cc: Robert Treat <rob@xzilla.net>, pgsql-hackers@postgresql.org
In-Reply-To: <4D1CF4E2.5000208@kaltenbrunner.cc>
References: <1293729972.1892.23804.camel@ebony>
	<4D1CC47E.7050207@kaltenbrunner.cc> <1293735853.1892.24886.camel@ebony>
	<AANLkTi=dr9TuYRLMWjPkJdL1Jjg+TAJXPJQbLGiN1Pag@mail.gmail.com>
	<1293741390.1892.25918.camel@ebony>
	<AANLkTim3mEVaP9eJsqticw600sSomHhJgsQVgjoDxASA@mail.gmail.com>
	<1293742878.1892.26205.camel@ebony> <4D1CF4E2.5000208@kaltenbrunner.cc>
Content-Type: text/plain; charset="UTF-8"
Date: Thu, 30 Dec 2010 21:27:11 +0000
Message-ID: <1293744431.1892.26514.camel@ebony>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit

On Thu, 2010-12-30 at 22:08 +0100, Stefan Kaltenbrunner wrote:
> On 12/30/2010 10:01 PM, Simon Riggs wrote:
> > On Thu, 2010-12-30 at 15:51 -0500, Robert Treat wrote:
> >
> >> Still, one thing that has me concerned is that in the case of two
> >> slaves, you don't know which one is the more up-to-date one if you
> >> need to failover. It'd be nice if you could just guarantee they both
> >> are...
> >
> > Regrettably, nobody can know that, without checking.
> 
> how exactly would you check? - this seems like something that needs to 
> be done from the SQL and the CLI level and also very well documented 
> (which I cannot see in your proposal).

This is a proposal for sync rep, not multi-node failover. I'm definitely
not going to widen the scope of this project.

Functions already exist to check the thing you're asking.

-- 
 Simon Riggs           http://www.2ndQuadrant.com/books/
 PostgreSQL Development, 24x7 Support, Training and Services