Package com.datastax.driver.core.policies

Interface AddressTranslator

  • All Known Implementing Classes:
    EC2MultiRegionAddressTranslator, IdentityTranslator
    public interface AddressTranslator
    Translates IP addresses received from Cassandra nodes into locally queriable addresses.

    The driver auto-detect new Cassandra nodes added to the cluster through server side pushed notifications and through checking the system tables. For each node, the address the driver will receive will correspond to the address set as rpc_address in the node yaml file. In most case, this is the correct address to use by the driver and that is what is used by default. However, sometimes the addresses received through this mechanism will either not be reachable directly by the driver or should not be the preferred address to use to reach the node (for instance, the rpc_address set on Cassandra nodes might be a private IP, but some clients may have to use a public IP, or pass by a router to reach that node). This interface allows to deal with such cases, by allowing to translate an address as sent by a Cassandra node to another address to be used by the driver for connection.

    Please note that the contact points addresses provided while creating the Cluster instance are not "translated", only IP address retrieved from or sent by Cassandra nodes to the driver are.

    • Method Detail

      • init

        void init​(Cluster cluster)
        Initializes this address translator.
        Parameters:
        cluster - the Cluster instance for which the translator is created.

      • translate

        InetSocketAddress translate​(InetSocketAddress address)
        Translates a Cassandra rpc_address to another address if necessary.
        Parameters:
        address - the address of a node as returned by Cassandra. Note that if the rpc_address of a node has been configured to 0.0.0.0 server side, then the provided address will be the node listen_address, *not* 0.0.0.0. Also note that the port for InetSocketAddress will always be the one set at Cluster construction time (9042 by default).
        Returns:
        the address the driver should actually use to connect to the node designated by address. If the return is null, then address will be used by the driver (it is thus equivalent to returning address directly)

      • close

        void close()
        Called at Cluster shutdown.