Multiple data center deployment

A deployment scenario with a mixed workload cluster has more than one data center for each type of node.

This configuration example describes installing a six node cluster spanning two data centers.

Set properties for each node in the cassandra.yaml file. This file is located in different places depending on the type of installation:

1. Suppose you install DataStax Enterprise on these nodes:
   • node0 10.168.66.41 (seed1)
   • node1 10.176.43.66
   • node2 10.168.247.41
   • node3 10.176.170.59 (seed2)
   • node4 10.169.61.170
   • node5 10.169.30.138
2. If the nodes are behind a firewall, open the required ports for internal/external communication. See Configuring firewall port access.
3. If DataStax Enterprise is running, stop the nodes and clear the data:
   • Packaged installs:

     $ sudo service dse stop
     $ sudo rm -rf /var/lib/cassandra/* ## Clears the data from the  default directories

   • Tarball installs:

     From the install directory:

     $ sudo bin/dse cassandra-stop
     $ sudo rm -rf /var/lib/cassandra/* ## Clears the data from the default directories

     Note: If you are clearing data from an AMI installation for restart, you need to preserve the log files.
4. Modify the following property settings in the cassandra.yaml file for each node:
   • num_tokens: 256 for Cassandra nodes
   • num_tokens: 1 for Hadoop and Solr nodes
   • -seeds: internal_IP_address of each seed node
   • listen_address: localhost_IP_address
   • auto_bootstrap: false (Add this setting only when initializing a fresh cluster with no data.)
   • Make sure that the following options are disabled, as they are no longer supported by DataStax Enterprise:

     ## Replication strategy to use for the auth keyspace.
     #auth_replication_strategy: org.apache.cassandra.locator.SimpleStrategy
     
     #auth_replication_options:
     #replication_factor: 1
     

     Note: If you have not disabled both auth_replication_strategy and replication_factor, you will see an error. For information about correcting this error, see Issues in the DataStax Enterprise 3.2.5 release notes.

   node0:

   cluster_name: 'MyDemoCluster'
   num_tokens: 256
   seed_provider:
     - class_name: org.apache.cassandra.locator.SimpleSeedProvider
       parameters:
            - seeds: "10.168.66.41,10.176.170.59"
   listen_address: 10.168.66.41

   Note: You must include at least one node from each data center. It is a best practice to have more than one seed node per data center.

   The properties for rest of the nodes are the same as node0 except for the listen_address:

   Node	listen_address
   node1	10.176.43.66
   node2	10.168.247.41
   node3	10.176.170.59
   node4	10.169.61.170
   node5	10.169.30.138

5. If necessary, change the dse.yaml file on each node to specify the snitch to be delegated by the DseDelegateSnitch. For more information about snitches, see the About Snitches. For example, to specify the PropertyFileSnitch:

   delegated_snitch: org.apache.cassandra.locator.PropertyFileSnitch

6. In the cassandra-topology.properties file, use your naming convention to assign data center and rack names to the IP addresses of each node, and assign a default data center name and rack name for unknown nodes. For example:

   # Cassandra Node IP=Data Center:Rack
   10.168.66.41=DC1:RAC1
   10.176.43.66=DC2:RAC1
   10.168.247.41=DC1:RAC1
   10.176.170.59=DC2:RAC1
   10.169.61.170=DC1:RAC1
   10.169.30.138=DC2:RAC1
   
   # default for unknown nodes
   default=DC1:RAC1

7. After you have installed and configured DataStax Enterprise on all nodes, start the seed nodes one at a time, and then start the rest of the nodes:
   • Packaged installs: See Starting DataStax Enterprise as a service.
   • Tarball installs: See Starting DataStax Enterprise as a stand-alone process.
   Note: If the node has restarted because of automatic restart, you must stop the node and clear the data directories, as described above.
8. Check that your cluster is up and running:
   • Packaged installs: $ nodetool status
   • Tarball installs: $ install_location/bin/nodetool status

Results