On 4/29/15 1:38 AM, Craig Ringer wrote:
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.
Replication identifiers do just that: provide a way to map identifiers
from some external system into a local unique identifier for a peer
node, along with tracking of the replay position from the peer so replay
can be restarted at a consistent point. The replay position is an LSN,
so they're not going to work for any arbitrary system, though.
Which may not work for something meant to work with different
replication systems...
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.
Yeah, you're talking about some kind of abstract modelling of a
replication topology. I'm not sure that's at all necessary to keep track
of which tables should be replicated to which nodes.
I'd think that you'd still need to know if a table is a provider or
subscriber regardless of topology; how else will you know how to add it?
As for the topology part, yes, perhaps that's more than the baseline
case. It might be enough of a win to just deal with tables and sets to
not worry about it.
I originally had this idea when dealing with a number of londiste
clusters and wishing I had something better than "Run this SELECT and
paste the output to the command line" to deal with adding newly created
tables. It seemed likely that a more generic system should also be
pretty easy to allow plugging into different replication systems;
there'd just need to be a different layer that translated definition
into actual replication commands. Then the only thing missing would be
defining what sets lived where; that would allow the generic system at
least define almost every aspect of a replication environment. Maybe
that's too ambitious; the first step would be to try just what tables
are in which set and see how that goes.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com
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