Initializing a multiple node cluster (multiple datacenters)

A deployment scenario for a Cassandra cluster with multiple datacenters.

1. Suppose you install Cassandra 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

   Note: It is a best practice to have more than one seed node per datacenter.
2. If you have a firewall running in your cluster, you must open certain ports for communication between the nodes. See Configuring firewall port access.
3. If Cassandra is running, you must stop the server and clear the data:

   Doing this removes the default cluster_name (Test Cluster) from the system table. All nodes must use the same cluster name.

   Package installations:

   1. Stop Cassandra:

      sudo service cassandra stop #Stops Cassandra

   2. Clear the data:

      sudo rm -rf /var/lib/cassandra/*

   Tarball installations:

   1. Stop Cassandra:

      ps auwx | grep cassandra

      sudo kill pid

   2. Clear the data:

      sudo rm -rf install_location/data/*

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

   Properties to set:

   • cluster_name:
   • num_tokens: recommended value: 8
   • -seeds: internal IP address of each seed node

     In new clusters. Seed nodes don't perform bootstrap (the process of a new node joining an existing cluster.)

   • listen_address:

     If the node is a seed node, this address must match an IP address in the seeds list. Otherwise, gossip communication fails because it doesn't know that it is a seed.

     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.

   • rpc_address:listen address for client connections
   • endpoint_snitch: name of snitch (See endpoint_snitch.) If you are changing snitches, see Switching snitches.

   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.

   Example:

   cluster_name: 'MyCassandraCluster'
   num_tokens: 8
   seed_provider:
     - class_name: org.apache.cassandra.locator.SimpleSeedProvider
       parameters:
            - seeds:  "10.168.66.41,10.176.170.59"
   listen_address:
   endpoint_snitch: GossipingPropertyFileSnitch

   Note: Include at least one node from each datacenter in the seeds list.
5. In the cassandra-rackdc.properties file, assign the datacenter and rack names you determined in the Prerequisites. For example:

   Nodes 0 to 2

   ## Indicate the rack and dc for this node
   dc=DC1
   rack=RAC1

   Nodes 3 to 5

   ## Indicate the rack and dc for this node
   dc=DC2
   rack=RAC1

6. After you have installed and configured Cassandra on all nodes, DataStax recommends starting 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 first stop the node and clear the directories, as described above.

   Package installations:

   sudo service cassandra start #Starts Cassandra

   Tarball installations:

   cd install_location

   bin/cassandra

7. To check that the ring is up and running, run:
   Package installations:

   nodetool status

   Tarball installations:

   cd install_location

   bin/nodetool status

   The output should list each node, and show its status as UN (Up Normal).

   

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

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