On Tue, Sep 7, 2010 at 17:42, kannan chandrasekaran <ckanna...@yahoo.com> wrote: > Hi All, > > We are currently considering Cassandra for our application. > > Platform: > * a single-node cluster. > * windows '08 > * 64-bit jvm > > For the sake of brevity let, > Cassandra service = a single node cassandra server running as an embedded > service inside a JVM > > > My use cases: > 1) Start with a schema ( keyspace and set of column families under it) in a > cassandra service > 2) Need to be able to replicate the same schema structure (add new > keyspace/columnfamilies with different names ofcourse). > 3) Because of some existing limitations in my application, I need to be able > to write to the keyspace/column-families from a cassandra service and read > the written changes from a different cassandra service. Both the write and > the read "cassandra-services" are sharing the same Data directory. I > understand that the application has to take care of any naming collisions. > > > Couple Questions related to the above mentioned usecases: > 1) I want to spawn a new JVM and launch Cassandra as an embedded service > programatically instead of using the startup.bat. I would like to know if > that is possible and any pointers in that direction would be really helpful. > ( use-case1)
There are a couple ways to do this. I've used two of them (tanuki and objectweb). Tanuki is better imo. I've never used it, but Apache procrun is probably worth checking out. > 2) I understand that there are provisions for live schema changes in 0.7 ( > thank you guys !!!), but since I cant use a beta version in production, I am > restricted to 0.6 for now. Is it possible to to support use-case 2 in 0.6.5 > ? More specifically, I am planning to make runtime changes to the > storage.conf xml file followed by a cassandra service restart Yes, but this is a manual process and will not scale well. > 3) Can I switch the data directory at run-time ? (use-case 3). In order to > not disrupt read while the writes are in progress, I am thinking something > like, copy the existing data-dir into a new location; write to a new data > directory; once the write is complete; switch pointers and restart the > cassandra service to read from the new directory to pick up the updated > changes > Pointing two cassandra instances at the same data directory? This is a bad idea. I've never tried it, so I don't know exactly what will happen, but I imagine you would corrupt your system tables pretty quickly and your commit log wouldn't be too happy either. This is a completely unsupported way of using cassandra. Gary
