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From Ananth Gundabattula <agundabatt...@threatmetrix.com>
Subject Merge two clusters into one - renaming an existing cluster
Date Mon, 24 Jun 2013 05:13:13 GMT
Hello Everybody,

I am trying to merge two clusters into a single cluster ( the rationale being easier administration
apart from better load balancing etc)

The plan is to rename a cluster (QAPERF1) as the same name as the second cluster (QAPERF2).
Then alter the cassandra-toppology.properties and make them appear as different Dcs. Then
finally alter replication settings and rebuild nodes of course after changing the seeds. It
is made sure that the schema is same across the  two clusters. This is a test on apache cassandra
1.2.4.

In the process of  renaming an existing cluster, I have followed the instructions here : http://wiki.apache.org/cassandra/FAQ#clustername_mismatch

I get the following when restarting the node after restarting the first node after cluster
name change ( The other nodes are yet to be restarted). It looks like the old cluster name
has not taken into effect in spite of completing the flush as mentioned in the wiki.

ERROR [main] 2013-06-24 04:44:35,812 CassandraDaemon.java (line 222) Fatal exception during
initialization
org.apache.cassandra.exceptions.ConfigurationException: Saved cluster name QAPERF1 != configured
name QAPERF2
at org.apache.cassandra.db.SystemTable.checkHealth(SystemTable.java:447)
at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:218)
at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:411)
at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:454)

In the process of reverting it back, I changed the configuration file back to have the old
cluster name and now I get this exception.

ERROR [main] 2013-06-24 04:48:34,746 CassandraDaemon.java (line 428) Exception encountered
during startup
java.util.NoSuchElementException
at java.util.ArrayList$Itr.next(ArrayList.java:794)
at org.apache.cassandra.db.SystemTable.upgradeSystemData(SystemTable.java:164)
at org.apache.cassandra.db.SystemTable.finishStartup(SystemTable.java:98)
at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:317)
at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:411)
at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:454)

Can experts please advise what is the best way to rename a cluster in case I want to change
it for version 1.2.4 ? Thanks for your time.

Regards,
Ananth

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