Re: Sync Rep Design

On Thu, Dec 30, 2010 at 3:36 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
> On Thu, 2010-12-30 at 15:07 -0500, Robert Treat wrote:
> > > If more than one standby server specifies synchronous_replication,
> > then
> > > whichever standby replies first will release waiting commits.
>
> > I don't want you to think I am setting an expectation, but I'm curious
> > about the possibility of requiring more than 1 server to reply?
>
> I was initially interested in this myself, but after a long discussion
> on "quorum commit" it was decided to go with "first past post".
>
> That is easier to manage, requires one less parameter, performs better
> and doesn't really add that much additional confidence.
>

Yes, I think with a single master, you are probably right (been
dealing with more than my fair share of multi-master based nosql
solutions lately)

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, but in lieu of that, I guess whatever decision tree is being
used, it needs to look at current xlog location of any potential
failover targets.

> It was also discussed that we would have a plugin API, but I'm less sure
> about that now. Perhaps we can add that option in the future, but its
> not high on my list of things for this release.
>

Agreed.

Robert Treat
http://www.xzilla.net