Apache Cassandra™ 2.0


Use the EC2MultiRegionSnitch for deployments on Amazon EC2 where the cluster spans multiple regions. As with the EC2Snitch, regions are treated as data centers and availability zones are treated as racks within a data center. For example, if a node is in us-east-1a, us-east is the data center name and 1a is the rack location.

You can also specify multiple data centers within an EC2 region using the dc_suffix property in the /etc/dse/cassandra/cassandra-rackdc.properties file. For example, if node1 and node2 are in us-east-1:
Node cassandra-rackdc.properties Data center
1 dc_suffix=_A us-east-1_A
2 dc_suffix=_B us-east-1_B

This snitch uses public IPs as broadcast_address to allow cross-region connectivity. This means that you must configure each Cassandra node so that the listen_address is set to the private IP address of the node, and the broadcast_address is set to the public IP address of the node. This allows Cassandra nodes in one EC2 region to bind to nodes in another region, thus enabling multiple data center support. (For intra-region traffic, Cassandra switches to the private IP after establishing a connection.)

Additionally, you must set the addresses of the seed nodes in the cassandra.yaml file to that of the public IPs because private IPs are not routable between networks. For example:


To find the public IP address, run this command from each of the seed nodes in EC2:

curl http://instance-data/latest/meta-data/public-ipv4

Finally, be sure that the storage_port or ssl_storage_port is open on the public IP firewall.

When defining your keyspace strategy options, use the EC2 region name, such as ``us-east``, as your data center names.