Connecting to a cluster with SSH port forwardings

establish_port_forwardings.sh

# Before running this demo, make sure that "Remote Login" is enabled on your macbook!

sudo ifconfig lo0 alias 127.0.0.2 up
sudo ifconfig lo0 alias 127.0.0.3 up

# Simulate a "remote" cluster with 3 nodes

ccm create -v 3.0.0 -n 3 ssh_demo
ccm start

# Establish port forwardings to each node:
# node 1 -> localhost:19042
# node 2 -> localhost:29042
# node 3 -> localhost:39042

node1="127.0.0.1"
node2="127.0.0.2"
node3="127.0.0.3"

# Caution: these tunnels will be automatically closed if idle for more than 5 minutes!

ssh -f -L 19042:localhost:9042 $node1 sleep 300
ssh -f -L 29042:localhost:9042 $node2 sleep 300
ssh -f -L 39042:localhost:9042 $node3 sleep 300

# Check that the ports are open:
 netstat -atp tcp | egrep "(19042|29042|39042)"

# Now, test the driver!

# Only when you are done testing, close all SSH tunnels:
killall ssh

SSHPortForwardingAddressTranslator.java

import com.datastax.driver.core.policies.AddressTranslator;

import java.net.InetSocketAddress;
import java.util.Map;

public class SSHPortForwardingAddressTranslator implements AddressTranslator {

    private final Map<InetSocketAddress, InetSocketAddress> portForwardings;

    public SSHPortForwardingAddressTranslator(Map<InetSocketAddress, InetSocketAddress> portForwardings) {
        this.portForwardings = portForwardings;
    }

    @Override
    public InetSocketAddress translate(InetSocketAddress remote) {
        InetSocketAddress local = portForwardings.get(remote);
        if (local == null) {
            System.err.println("Cannot find local port forwarding for node "
                    + remote + ". The driver will not be able to connect to this node.");
            return remote;
        }
        return local;
    }

    @Override
    public void init(Cluster cluster) {
    }

    @Override
    public void close() {
    }
}

SSHPortForwardingDemo.java

import com.google.common.collect.ImmutableMap;
import java.net.InetSocketAddress;
import java.util.Map;

public class SSHPortForwardingDemo {

    // These should reflect the ports used when establishing port forwardings with SSH
    static final Map<InetSocketAddress, InetSocketAddress> PORT_FORWARDINGS = ImmutableMap.of(
            // distant                                // local
            new InetSocketAddress("127.0.0.1", 9042), new InetSocketAddress("localhost", 19042),
            new InetSocketAddress("127.0.0.2", 9042), new InetSocketAddress("localhost", 29042),
            new InetSocketAddress("127.0.0.3", 9042), new InetSocketAddress("localhost", 39042)
    );

    public static void main(String[] args) {
        Cluster cluster = null;
        try {

            cluster = Cluster.builder()
                    // cluster will talk to local addresses only
                    .addContactPointsWithPorts(PORT_FORWARDINGS.values())
                    // use a translator to map distant addresses to local ones
                    .withAddressTranslator(new SSHPortForwardingAddressTranslator(PORT_FORWARDINGS))
                    .build();

            cluster.init();

            // prints all hosts with their respective ports
            System.out.println("Successfully connected!");
            System.out.println("Nodes in this cluster (as they appear to the driver):");
            System.out.println(cluster.getMetadata().getAllHosts());

        } finally {
            if (cluster != null)
                cluster.close();
        }
    }

}