Re: BDR Selective Replication

On 4/27/15 7:54 PM, Craig Ringer wrote:

    If 'default replication set' is the idea of "here's what tables
    *should* be getting replicated regardless of whether that's
    happening or not", it'd be great if that was done so it could be
    split out on it's own at some point. It's a problem that affects all
    replication systems.


It wasn't, but that's an interesting idea.

You need  away to identify peer nodes in an abstract way before you can
really define sets of which nodes should get which tables. So I think
replication identifiers ( https://commitfest.postgresql.org/4/161/ ) are
a pre-requisite for that though, and one that's proving difficult to get
in.

Perhaps... different replication systems probably use different methods to identify, so presumably there'd need to be some way to map a generic identifier into an appropriate identifier for whatever replication system you're using.

How would you want to go about storing and tracking the information? A
new catalog? The other issue for in-core replication sets would probably
be making it foreign-key aware, so replication of a table transitively
requires replication of its references.

As you said, we'd need a way to identify replication nodes. We might also need/want a way to specify topology.

I don't think topology would be too hard (presumably it's either a single 'parent' node, or a list of peers). What might be more interesting is dealing with different systems methods of identifying nodes.

You'd want a way to define different sets and associate them with nodes. A node could be a provider, subscriber, or both. I think some replication systems support 'pass through' as well, where the node passes data downstream but doesn't apply it itself. Or it could be multi-master and possibly a provider to read-only subscribers.