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 6 node cluster spanning 2 data centers. The default consistency level is QUORUM.

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. Set the properties in the cassandra.yaml file for each node.
   Important: After making any changes in the cassandra.yaml file, you must restart the node for the changes to take effect.
   Location:

   • Packaged installs: /etc/dse/cassandra/cassandra.yaml
   • Tarball installs: install_location/resources/cassandra/conf/cassandra.yaml

   Properties to set:

   Note: If the nodes in the cluster are identical in terms of disk layout, shared libraries, and so on, you can use the same copy of the cassandra.yaml file on all of them.
   • num_tokens: 256 for Cassandra nodes
   • num_tokens: 1 for Hadoop and Solr nodes
   • -seeds: internal_IP_address of each seed node
   • listen_address: empty

     If not set, Cassandra asks the system for the local address, the one associated with its hostname. In some cases Cassandra doesn't produce the correct address and you must specify the listen_address.

   • auto_bootstrap: false (Add this setting only when initializing a fresh cluster with no data.)
   • If you are using a cassandra.yaml from a previous version, remove the following options, 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

   Example:

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

   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:

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.
   • Packaged installs: /etc/dse/dse.yaml
   • Tarball installs: install_location/resources/dse/conf/dse.yaml

   Example of specifying 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.
   • Packaged installs: /etc/dse/cassandra/cassandra-topology.properties
   • Tarball installs: install_location

   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