Multiple datacenter deployment per workload type

Steps for configuring nodes in a deployment scenario in a mixed workload cluster that has more than one datacenter 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:
   • Installer-Services and Package installations:

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

   • Installer-No Services and Tarball installations:

     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:
   The location of the cassandra.yaml file depends on the type of installation:

   Package installations	/etc/dse/cassandra/cassandra.yaml
   Tarball installations	install_location/resources/cassandra/conf/cassandra.yaml

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

   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 DSE Search nodes
   • num_tokens: 64 to 256 for DSE Search nodes when using vnodes; otherwise num_tokens: 1
   • -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 host name. In some cases Cassandra doesn't produce the correct address and you must specify the listen_address.

   • endpoint_snitch: snitch See endpoint_snitch. If you are changing snitches, see Switching snitches.
   • auto_bootstrap: false

     Add the bootstrap setting only when initializing a fresh cluster with no data.

   • endpoint_snitch: snitch

     For more information, see endpoint_snitch and About Snitches.

   • If you are using a cassandra.yaml file 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 datacenter. It is a best practice to have more than one seed node per datacenter.

   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:
   endpoint_snitch: GossipingPropertyFileSnitch

5. In the cassandra-rackdc.properties (GossipingPropertyFileSnitch) or cassandra-topology.properties (PropertyFileSnitch) file, use your naming convention to assign datacenter and rack names to the IP addresses of each node, and assign a default datacenter name and rack name for unknown nodes.
   The default location of the cassandra-topology.properties file depends on the type of installation:

   Installer-Services and Package installations	/etc/dse/cassandra/cassandra-topology.properties
   Installer-No Services and Tarball installations	install_location/resources/cassandra/conf/cassandra-topology.properties

   The default location of the cassandra-rackdc.properties file depends on the type of installation:

   Installer-Services and Package installations	/etc/dse/cassandra/cassandra-rackdc.properties
   Installer-No Services and Tarball installations	install_location/resources/cassandra/conf/cassandra-rackdc.properties

   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

6. 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:
   • Packages/Services: See Starting DataStax Enterprise as a service.
   • Tarball/No Services: 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.
7. Check that your cluster is up and running:
   • Installer-Services and Package installations: $ nodetool status
   • Installer-No Services and Tarball installations: $ install_location/bin/nodetool status

Datacenter: DC1
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address          Load        Tokens    Owns    Host ID             Rack
UN 10.168.66.41     45.96 KB    256       27.4%   c885aac7-f2c0-...   RAC1
UN 10.168.247.41    66.34 KB    256       36.6%   fa31416c-db22-...   RAC1
UN 10.169.61.170    55.72 KB    256       33.0%   f488367f-c14f-...   RAC1
Datacenter: DC2
=======================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address          Load        Tokens    Owns    Host ID             Rack
UN 10.176.43.66     45.96 KB    256       27.4%   f9fa31c7-f3c0-...   RAC1
UN 10.176.170.59    66.34 KB    256       36.6%   a5bb526c-db51-...   RAC1
UN 10.169.30.138    55.72 KB    256       33.0%   b836478f-c49f-...   RAC1