Package org.apache.hadoop.net

Interface DNSToSwitchMapping

All Known Implementing Classes:
AbstractDNSToSwitchMapping, CachedDNSToSwitchMapping, ScriptBasedMapping, TableMapping
@Public @Evolving public interface DNSToSwitchMapping
An interface that must be implemented to allow pluggable DNS-name/IP-address to RackID resolvers.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    reloadCachedMappings()
    Reload all of the cached mappings.
    void
    reloadCachedMappings(List<String> names)
    Reload cached mappings on specific nodes.
    List<String>
    resolve(List<String> names)
    Resolves a list of DNS-names/IP-addresses and returns back a list of switch information (network paths).

  • Method Details

    • resolve

      List<String> resolve(List<String> names)
      Resolves a list of DNS-names/IP-addresses and returns back a list of switch information (network paths). One-to-one correspondence must be maintained between the elements in the lists. Consider an element in the argument list - x.y.com. The switch information that is returned must be a network path of the form /foo/rack, where / is the root, and 'foo' is the switch where 'rack' is connected. Note the hostname/ip-address is not part of the returned path. The network topology of the cluster would determine the number of components in the network path.

      If a name cannot be resolved to a rack, the implementation should return NetworkTopology.DEFAULT_RACK. This is what the bundled implementations do, though it is not a formal requirement

      Parameters:
      names - the list of hosts to resolve (can be empty)
      Returns:
      list of resolved network paths. If names is empty, the returned list is also empty

    • reloadCachedMappings

      void reloadCachedMappings()
      Reload all of the cached mappings. If there is a cache, this method will clear it, so that future accesses will get a chance to see the new data.

    • reloadCachedMappings

      void reloadCachedMappings(List<String> names)
      Reload cached mappings on specific nodes. If there is a cache on these nodes, this method will clear it, so that future accesses will see updated data.
      Parameters:
      names - input names.