Re: Configuring synchronous replication

Robert Haas <robertmhaas@gmail.com> writes:
> Now, admittedly, in more complex topologies, and especially if you're
> using configuration options that pertain to the behavior of
> disconnected standbys (e.g. wait for them, or retain WAL for them),
> you're going to need to adjust the configs.  But I think that's likely
> to be true anyway, even with a catalog.  If A is doing sync rep and
> waiting for B even when B is disconnected, and the machines switch
> roles, it's hard to see how any configuration isn't going to need some
> adjustment.  One thing that's nice about the flat file system is that
> you can make the configuration changes on the new master before you
> promote it

Actually, that's the killer argument in this whole thing.  If the
configuration information is in a system catalog, you can't change it
without the master being up and running.  Let us suppose for example
that you've configured hard synchronous replication such that the master
can't commit without slave acks.  Now your slaves are down and you'd
like to change that setting.  Guess what.
        regards, tom lane