Address resolution

The driver auto-detects new Cassandra nodes when they are added to the cluster by means of server-side push notifications and checking the system tables.

For each node, the address the driver receives the address set as rpc_address in the node’s cassandra.yaml file (or broadcast_rpc_address when defined). In most cases, this is the correct value, however, sometimes the addresses received in this manner are either not reachable directly by the driver or are not the preferred address to use. A common such scenario is a multi-datacenter deployment with a client connecting using the private IP address to the local datacenter (to reduce network costs) and the public IP address for the remote datacenter nodes.

The AddressTranslator interface

The IAddressTranslator interface allows you to deal with such cases, by transforming the address sent by a Cassandra node to another address to be used by the driver for connection.

namespace Cassandra
{
    public interface IAddressTranslator
    {
        IPEndPoint Translate(IPEndPoint address);
    }
}

You then configure the driver to use your IAddressTranslator implementation in the client options.

var cluster = Cluster.Builder()
    .AddContactPoint("1.2.3.4")
    .WithAddressTranslator(new MyAddressTranslator())
    .Build();

Note: The contact points provided while building the Cluster are not translated, only addresses retrieved from or sent by Cassandra nodes are.