On Mon, 2010-09-20 at 22:42 +0100, Thom Brown wrote:
> On 20 September 2010 22:14, Robert Haas <robertmhaas@gmail.com> wrote:
> > Well, if you need to talk to "all the other standbys" and see who has
> > the furtherst-advanced xlog pointer, it seems like you have to have a
> > list somewhere of who they all are.
>
> When they connect to the master to get the stream, don't they in
> effect, already talk to the primary with the XLogRecPtr being relayed?
> Can the connection IP, port, XLogRecPtr and request time of the
> standby be stored from this communication to track the states of each
> standby? They would in effect be registering upon WAL stream
> request... and no doubt this is a horrifically naive view of how it
> works.
It's not viable to record information at the chunk level in that way.
But the overall idea is fine. We can track who was connected and how to
access their LSNs. They don't need to be registered ahead of time on the
master to do that. They can register and deregister each time they
connect.
This discussion is reminiscent of the discussion we had when Fujii first
suggested that the standby should connect to the master. At first I
though "don't be stupid, the master needs to connect to the standby!".
It stood everything I had thought about on its head and that hurt, but
there was no logical reason to oppose. We could have used standby
registration on the master to handle that, but we didn't. I'm happy that
we have a more flexible system as a result.
-- Simon Riggs www.2ndQuadrant.comPostgreSQL Development, 24x7 Support, Training and Services
