Cassandra Migration(Version 1.X)

 Steps taken in Existing Cassandra Cluster.
===========================
1) Take snapshot of keyspace, backup schema and also copy backups folder under
keyspace directory if incremental backup is enabled in the existing cluster.

Take a snapshot of keyspace.
============================
nodetool snapshot -t my_snapshot_tag

Backup keyspace schema
======================

echo -e "use your_keyspace;\r\n show schema;\n" | bin/cassandra-cli -h localhost >
mySchema.cdl

Copy backups folder under keyspace
==================================

tar -cvzf backups.tar.gz /var/lib/cassandra/data/keyspace_name/backups

2) Note the token enabled in the existing cluster

./nodetool ring -h localhost                           Address         DC         
Rack        Status State   Load            Owns    Token                            
                                                                               85070591730234615865843651857942052863
193.41.xx.xx   datacenter1 rack1       Up     Normal  2.24 GB         50.00%  1    
                           
193.41.xx.yy   datacenter1 rack1       Up     Normal  2.18 GB         50.00% 
85070591730234615865843651857942052863

Here the token enabled in node1 is 85070591730234615865843651857942052863 and node2
is 1




Steps to do in New Cassandra Cluster
==============================

1) Stop cassandra cluster 

kill -9 <cassandra process>

2) Delete system keyspace data files

rm -rf /var/lib/cassandra/data/system/

a) delete commit_log (var/lib/cassandra/commitlog)
b) saved_cache  (/var/lib/cassandra/saved_caches)
c) clear contents in /var/lib/cassandra/data/<keyspace>

3) Disable auto_bootstrap to false in cassandra.yaml

auto_bootstrap: false

4) Put initial_token with the values as same as that in existing cluster to
cassandra.yaml (noted values in step2 of exisiting cluster)

5) Make sure that below parameter is false in cassandra-env.sh

JVM_OPTS="$JVM_OPTS -Dcassandra.load_ring_state=false 

If there is no entry, please leave as it is.

6) Start the cluster and run below command.

./nodetool ring -h localhost 

Make sure that token is showing as same as that of existing cluster

7) Restore the schema file in node1 from existing cluster.

bin/cassandra-cli -h localhost -f mySchema.cdl

Make sure that the same schema is loaded in node2 automatically, otherwise restore
it in node2 as well.

8) Stop the cluster and restore data.

a) Locate the most recent snapshot folder in
<data_directory_location>/<keyspace_name>/snapshots/<snapshot_name>, and copy its
contents into <data_directory_location>/<keyspace_name>.

b) If using incremental backups as well, copy all contents of
<data_directory_location>/<keyspace_name>/backups into
<data_directory_location>/<keyspace_name>.

9) Start cassandra and refresh tables again.

 for x in `cat /root/cassandra/webax_tables.txt`; do ./nodetool -h localhost refresh
webax_ekp_staging $x;done;


That's it.