On Sat, Apr 3, 2010 at 3:41 PM, Mike Gallamore <mike.e.gallam...@googlemail.com> wrote: > > Useful things that nodes could advertise: > > data-centre they are in,
This is what the snitches do. > performance info: mem, CPU etc (these could be used to more intelligently > decide how to partition the data that the new node gets for example) Not convinced this is useful as it changes rapidly, so either causes lots of gossip or is always out of date. Better to use a real monitoring system. > geographical info Snitches. > perhaps a preferred hash range not just a token (and presumably everything > else would automatically rebalance itself to make that happen) > Unclear what this would do. > P.S.The last two could be useful for someone if they had their data in > Cassandra but it was more relevant more local to the geography. Think of > something like Craigslist. Having the data corresponding to San Fransisco > lists just happen to bootstrap over to a datacenter on the east coast > wouldn't be very efficient. But having two completely separate datastores > might not be the simplest design either. It would be nice to just tell the > datastore where the info is most relevant and have it make intelligent > choices of where to store things for you. > Or just set the token specifically for each node you bootstrap. Starting a node and crossing your fingers on its token selection is a recipe for interesting times :) > In my case we are making a reputation system. It would be nice if we had a > way to make sure that at least one replica of the data stayed on the > customers machine and one or more copies over on our servers. I don't know > how to do that and the reverse would be important too make sure other > customers data doesn't get replicated to another customers node. I guess > rather than a ring topology I'd like to try to get a star "everything in the > center + location specific info at the points". An option would be to use > different datastores at both ends and push updates over to the central store > which would be Cassandra but that isn't as transparent as just having > Cassandra nodes everywhere and just have the replication happen in a smart > way. This is what placement strategies do. Have a look at the RackAwareStrategy, for example. b
