On 2014-07-12 14:37:02 +0200, Martin Gudmundsson wrote: > > It's possible to do it to a streaming replication sync standby, but also > > to another BDR node. The logical decoding facility added in 9.4 allows > > logical replication solutions to use the same mechanism as streaming rep > > does. > > > > Sounds interesting, but it does not sound like it’s being bi-directional in that case? It is bidirectional if you configure a bdr node in synchronous_standby_names. Note that streaming replication's synchronous mode probably doesn't give the guarantees you're thinking it does: a) A sent commit might succeed locally on the primary, but the system might fail to send it to the synchronous standby. I.e. postgres' synchronous replication of normal commits is *not* 2-safe. b) Even if a transaction is replicated to the standby it's *not* guaranteed to be applied. All that's guaranteed is that it has been shipped to the synchronous standby. > Ideally I’m looking for a solution where I can run an application and it does not really matter on what node a transaction executes, or if it changes data or not. I'd like that too, but I don't think that's going to happen. There's just too many caveats (CAP theorem et al) to make that generally useful/applicable. I think we (as in postgres) will probably get the ability to run individual transactions in such a mode, but you surely wouldn't want to run every transaction in it. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
