Hello, If two different instances of cassandra are running on separate machines, but both are unfortunately configured to use the default cluster name, "Test Cluster", do they gang up as one cluster (even though they were intended to be two separate stand-alone instances), so that dropping keyspace on one machine would result in the disappearance of data from the other?
We ran into some mysterious data disappearance situations -- and we are not sure if this is something with our configuration. We installed 2 instances of cassandra 0.8.2 on 2 separate machines, one is silk.cs.our.domain and the other smoke.cs.our.domain. Both the code and data directories reside on the local partition of each machine, and we left the the yaml file pretty much the default, except we changed the data directory paths and also the listen addresses to point to each host. What I want to point out is, both files had the default cluster name "Test Cluster". Both cassandra instances were loaded with identical keyspaces, data sets, and the intention was one would be used as production and the other testing cassandra server. Then yesterday we were trying to drop a keyspace on silk, which was the testing server, and sometimes later, a user complained that he could not get any data from the production machine. We were intrigued but thought maybe someone made a mistake. Then the same thing happened again today. So we began to suspect that two servers somehow discovered each other. In fact, after we shut down the cassandra on silk, and then load a keyspace definition into smoke using cassandra-cli, it even said unreachable destination and the IP was that of silk. I just want to confirm that the culprit was because we used the same cluster name for both machines. So in other words, if we want to launch two separate instances of cassandra and keep them separate, we must make sure each uses a different cluster name or else they will gang up into the same cluster? But how do they even discover each other? Can someone enlighten me please? Thanks. -- Y.
