Dave, the HA MBean, see http://docs.neo4j.org/chunked/snapshot/operations-monitoring.html is giving you information about what instance currently being master, so you can use that information to set up your load balancing. Would that work?
Cheers, /peter neubauer GTalk: neubauer.peter Skype peter.neubauer Phone +46 704 106975 LinkedIn http://www.linkedin.com/in/neubauer Twitter http://twitter.com/peterneubauer http://www.neo4j.org - Your high performance graph database. http://startupbootcamp.org/ - Öresund - Innovation happens HERE. http://www.thoughtmade.com - Scandinavia's coolest Bring-a-Thing party. On Sat, Aug 20, 2011 at 2:55 AM, David Rader <dra...@allianceglobalservices.com> wrote: > In order to configure a load balancer to target all reads or all writes to > the master in an HA - what's the best way to do this? > > For instance, if you had a single source of updates and many clients reading > you might want to load balance the slaves as read-only and have the updates > all flow to the master node. Since the master is elected and will change > after a crash, what's the best way to "see" which node is the master and > dynamically update a load balancer to correctly direct traffic? > Or, what's the best way to update DNS entries to point to a > master.neocluster.company.com vs. slave.neocluster.company.com or such? > > Thanks > Dave > > > Date: Fri, 19 Aug 2011 11:12:05 +0300 > From: Tuure Laurinolli <tuure.laurino...@portalify.com> > Subject: Re: [Neo4j] HA consistency > To: Neo4j user discussions <user@lists.neo4j.org> > Message-ID: <4d3381ef-89dc-402f-9efe-77d72131e...@portalify.com> > Content-Type: text/plain; charset=us-ascii > > > On Aug 19, 2011, at 07:57 , David Rader wrote: > >> It looks like the HA implementation is for eventual consistency, tunable by >> how often a slave polls the master for updates from other nodes. >> >> With a load balanced cluster, is the best practice to simply use sticky >> sessions on clients to ensure that immediate reads of updated data are >> served by the same node that wrote the update and are therefore consistent? >> Any other recommended approaches? > > If your goal is HA, there are two other approaches: > > 1) Always read from master > > and > > 2) Always take read lock on things you read > > Always reading from master works because writes are synchronously replicated > to master, and taking a read lock works because taking a read lock always > synchronizes with master (although it of course also disallows related writes > for the duration of your transaction). These solutions affect write > performance (reading from master consumes master capacity, and taking read > locks prevents other transactions from completing). Read performance is > certainly affected as well compared to sticky sessions, and is likely to be > considerably lower because of the synchronization requirements, and load on > master. > > Consistency guarantees would be as follows: > > - Reading from arbitrary slaves guarantees very little > - Sticky sessions guarantee read-everything-up-until-your-previous-write > - Reading from master guarantees consistency re: communications over side > channels (if another node, after committing, tells you that he wrote > something, you can see that write, or possibly some newer write) > - Taking read locks guarantees > read-everything-up-until-your-previous-lock-request and also repeatable reads > _______________________________________________ > Neo4j mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user > _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
