Re: [Neo4j] HA Consistency
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
Re: [Neo4j] HA consistency
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
Re: [Neo4j] HA Consistency
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] HA consistency
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? How much overhead is there If you set the poll interval to a low duration, 1 sec or less? Thanks for your help David Rader ___ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
