Initializing a Multiple Node Cluster in a Single Data Center¶

Prerequisites¶

To correctly configure a multi-node cluster, requires the following:

• Cassandra is installed on each node.
• The total number of nodes in the cluster.
• A name for the cluster.
• The IP addresses of each node in the cluster.
• Which nodes will serve as the seed nodes. (Cassandra nodes use this host list to find each other and learn the topology of the ring.)
• The snitch you plan to use.
• If the nodes are behind a firewall, make sure you know what ports you need to open. See Configuring Firewall Port Access.
• Other configuration settings you may need are described in Choosing Node Configuration Options and Node and Cluster Configuration (cassandra.yaml).

This information is used to configure the Node and Cluster Initialization Properties in the cassandra.yaml configuration file on each node in the cluster. Each node should be correctly configured before starting up the cluster.

Configuration Example¶

This example describes installing a six node cluster spanning two racks in a single data center.

You set properties for each node in the cassandra.yaml file. The location of this file depends on the type of installation; see Cassandra Configuration Files Locations or DataStax Enterprise Configuration Files Locations.

To configure a mixed-workload cluster:

1. The nodes have the following IPs, and one node per rack will serve as a seed:

   • node0 110.82.155.0 (seed1)
   • node1 110.82.155.1
   • node2 110.82.155.2
   • node3 110.82.156.3 (seed2)
   • node4 110.82.156.4
   • node5 110.82.156.5

2. Calculate the token assignments using the Token Generating Tool.

   Node	Token
   node0	0
   node1	28356863910078205288614550619314017621
   node2	56713727820156410577229101238628035242
   node3	85070591730234615865843651857942052864
   node4	113427455640312821154458202477256070485
   node5	141784319550391026443072753096570088106

3. If you have a firewall running on the nodes in your cluster, you must open certain ports to allow communication between the nodes. See Configuring Firewall Port Access.

4. Stop the nodes and clear the data.

   • For packaged installs, run the following commands:

     $ sudo service cassandra stop (stops the service)

     $ sudo rm -rf /var/lib/cassandra/* (clears the data from the default directories)

   • For binary installs, run the following commands from the install directory:

     $ ps auwx | grep cassandra (finds the Cassandra Java process ID [PID])

     $ sudo kill <pid> (stops the process)

     $ sudo rm -rf /var/lib/cassandra/* (clears the data from the default directories)

5. Modify the following property settings in the cassandra.yaml file for each node:

   Note

   In the - seeds list property, include the internal IP addresses of each seed node.

   node0

   cluster_name: 'MyDemoCluster'
   initial_token: 0
   seed_provider:
     - class_name: org.apache.cassandra.locator.SimpleSeedProvider
       parameters:
            - seeds: "110.82.155.0,110.82.155.3"
   listen_address: 110.82.155.0
   rpc_address: 0.0.0.0
   endpoint_snitch: RackInferringSnitch
   

   node1 to node5

   The properties for the rest of the nodes are the same as Node0 except for the initial_token and listen_address:

   node1

   initial_token: 28356863910078205288614550619314017621
   listen_address: 110.82.155.1
   

   node2

   initial_token: 56713727820156410577229101238628035242
   listen_address: 110.82.155.2
   

   node3

   initial_token: 85070591730234615865843651857942052864
   listen_address: 110.82.155.3
   

   node4

   initial_token: 113427455640312821154458202477256070485
   listen_address: 110.82.155.4
   

   node5

   initial_token: 141784319550391026443072753096570088106
   listen_address: 110.82.155.5
   

6. After you have installed and configured Cassandra on all nodes, start the seed nodes one at a time, and then start the rest of the nodes.

   Note

   If the node has restarted because of automatic restart, you must stop the node and clear the data directories, as described in above.

   • Packaged installs: sudo service cassandra start

   • Binary installs, run one of the following commands from the install directory:

     bin/cassandra (starts in the background)

     bin/cassandra -f (starts in the foreground)

7. Check that your ring is up and running:

   • Packaged installs: nodetool ring -h localhost

   • Binary installs:

     cd /<install_directory>

     $ bin/nodetool ring -h localhost

   The ring status is displayed. This can give you an idea of the load balanced within the ring and if any nodes are down. If your cluster is not properly configured, different nodes may show a different ring; this is a good way to check that every node views the ring the same way.