Cassandra: Alter keyspace: Change keyspace replication strategy

You can change the replication strategy of the keyspace using ‘ALTER KEYSPACE’ command.

Syntax

ALTER  KEYSPACE keyspace_name 
   WITH REPLICATION = { 
      'class' : 'SimpleStrategy', 'replication_factor' : N  
     | 'class' : 'NetworkTopologyStrategy', 'dc1_name' : N [, ...] 
   }
   [AND DURABLE_WRITES =  true|false] ;

For example, let me create a key space ‘cassandratutorial’ with 'SimpleStrategy'.

CREATE keyspace cassandratutorial WITH REPLICATION =

{

         'class' : 'SimpleStrategy',

         'replication_factor' : 3

};

cqlsh> CREATE keyspace cassandratutorial WITH REPLICATION = 
   ... { 
   ... 'class' : 'SimpleStrategy', 
   ... 'replication_factor' : 3 
   ... };
cqlsh> 
cqlsh> DESCRIBE cassandratutorial;

CREATE KEYSPACE cassandratutorial WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '3'}  AND durable_writes = true;

Now, you can change the replication strategy of the keyspace ‘cassandratutorial’ by executing below command.

ALTER KEYSPACE cassandratutorial WITH REPLICATION = {

         'class' : 'NetworkTopologyStrategy',

         'bangalore' : 3, //Datacenter 1

         'tokyo' : 2, //Datacenter 2

         'berlin' : 3 //Datacenter 3

 };

cqlsh> ALTER KEYSPACE cassandratutorial WITH REPLICATION = { 
   ... 'class' : 'NetworkTopologyStrategy', 
   ... 'bangalore' : 3, //Datacenter 1
   ... 'tokyo' : 2, //Datacenter 2
   ... 'berlin' : 3 //Datacenter 3 
   ...  };
cqlsh> 
cqlsh> DESCRIBE cassandratutorial;

CREATE KEYSPACE cassandratutorial WITH replication = {'class': 'NetworkTopologyStrategy', 'bangalore': '3', 'berlin': '3', 'tokyo': '2'}  AND durable_writes = true;

Note

You should run the command 'nodetool repair -full keyspace', once replication strategy is changed.

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