On 07/12/2014 02:24 PM, Martin Gudmundsson wrote: > > 12 jul 2014 kl. 04:58 skrev Craig Ringer <craig@xxxxxxxxxxxxxxx>: > >> PgJDBC actually already supports rudimentary client-based failover. > > I’ve seen some mailing list threads regarding this but was that ever implemented? Do you know where it’s documented? I don't think the patch ever got accompanying documentation. It's not mentioned here, anyway: http://jdbc.postgresql.org/documentation/93/connect.html Failover URLs are of the form: jdbc:postgresql://host1:port1,host2:port2/dbnjame with the port being optional. I'll document that now, before I get caught up in working on something else. In case you're looking, the code was added by git bddc05f939ac9227b682e85d1ba0a9b902da814c . > Any ideas giving BDR an option to be synchronous. I mean in ”close quarters” with low latency it should work ok. BDR doesn't do synchronous replication _yet_, but it's on the roadmap. Right now BDR as a whole is in its early days; the feature is being shaped by feedback and the requirements of sponsors and contributors. It's changing quite quickly, which is one good reason most of it is implemented as a plugin to PostgreSQL. Synchronous replication is one of a number of things that the team has looked into but hasn't prioritized implementing yet. Out of interest, what sorts of problems are you interested in solving using BDR? What needs are you trying to meet? Are you looking to use it for scaling? For HA? For data protection/redundancy? For transparent distributed databases (client/node locality)? I'm curious about what part you see synchronous replication support for BDR playing in any deployment you're contemplating. > Great explanation. Making them sticky i most likely the most reasonable approach in our case. But it would be good to have a place to list of servers to try on startup and then stick to one. Perhaps the rudimentary support you mention above would do it? If you're using PgJDBC, then you can provide a list of servers in priority order in your JDBC URL, as shown above. It'll connect to the first available server. When time and priorities permit I'd love to tackle things like round-robin server allocation for connections, smart server selection with failover policies, etc. Those are non-trivial projects, though, and must be done for each driver. > Phew, C oh C, that was a while a go :-) Or Java, if you're into that side of things. PgJDBC is a pretty friendly codebase. -- Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
