Using multiple network interfaces

Configuring cassandra.yaml for multiple networks or across regions in cloud implementations

In multiple networks or cross-region cloud scenarios, communication between datacenters can only take place using an external IP address. The external IP address is defined in the cassandra.yaml file using the broadcast_address setting. Configure each node as follows:

1. In the cassandra.yaml, set the listen_address to the private IP address of the node, and the broadcast_address to the public address of the node.

   This allows Cassandra nodes to bind to nodes in another network or region, thus enabling multiple data-center support. For intra-network or region traffic, Cassandra switches to the private IP after establishing a connection.

2. Set the addresses of the seed nodes in the cassandra.yaml file to that of the public IP. Private IP are not routable between networks. For example:

   seeds: 50.34.16.33, 60.247.70.52

   Note: Do not make all nodes seeds, see Internode communications (gossip).
3. Be sure that the storage_port or ssl_storage_port is open on the public IP firewall.

Additional cassandra.yaml configuration for non-EC2 implementations

listen_on_broadcast_address: true

Configuring the snitch for multiple networks

External communication between the datacenters can only happen when using the broadcast_address (public IP).

The GossipingPropertyFileSnitch is recommended for production. The cassandra-rackdc.properties file defines the datacenters used by this snitch. Enable the option prefer_local to ensure that traffic to broadcast_address will re-route to listen_address.

For each node in the network, specify its datacenter in cassandra-rackdc.properties file.

In the example below, there are two cassandra datacenters and each datacenter is named for its workload. The datacenter naming convention in this example is based on the workload. You can use other conventions, such as DC1, DC2 or 100, 200. (datacenter names are case-sensitive.)

Configuring the snitch for cross-region communication in cloud implementations

In cloud deployments, the region name is treated as the datacenter name and availability zones are treated as racks within a datacenter. For example, if a node is in the us-east-1 region, us-east is the datacenter name and 1 is the rack location. (Racks are important for distributing replicas, but not for datacenter naming.)

In the example below, there are two cassandra datacenters and each datacenter is named for its workload. The datacenter naming convention in this example is based on the workload. You can use other conventions, such as DC1, DC2 or 100, 200. (datacenter names are case-sensitive.)

For each node, specify its datacenter in the cassandra-rackdc.properties. The dc_suffix option defines the datacenters used by the snitch. Any other lines are ignored.

us-east_1_cassandra
us-east_2_cassandra
us-east_1_analytics
us-east_1_search

us-west_1_cassandra
us-west_2_cassandra
us-west_1_analytics
us-west_1_search