Package org.apache.hadoop.net

Class CachedDNSToSwitchMapping

java.lang.Object
org.apache.hadoop.net.AbstractDNSToSwitchMapping
org.apache.hadoop.net.CachedDNSToSwitchMapping
All Implemented Interfaces:
Configurable, DNSToSwitchMapping
Direct Known Subclasses:
ScriptBasedMapping, TableMapping
@Public @Evolving public class CachedDNSToSwitchMapping extends AbstractDNSToSwitchMapping
A cached implementation of DNSToSwitchMapping that takes an raw DNSToSwitchMapping and stores the resolved network location in a cache. The following calls to a resolved network location will get its location from the cache.

  • Field Details

  • Constructor Details

    • CachedDNSToSwitchMapping

      public CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping)
      cache a raw DNS mapping
      Parameters:
      rawMapping - the raw mapping to cache

  • Method Details

    • resolve

      public List<String> resolve(List<String> names)
      Description copied from interface: DNSToSwitchMapping
      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

    • getSwitchMap

      public Map<String,String> getSwitchMap()
      Get the (host x switch) map.
      Overrides:
      getSwitchMap in class AbstractDNSToSwitchMapping
      Returns:
      a copy of the cached map of hosts to rack

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • isSingleSwitch

      public boolean isSingleSwitch()
      Delegate the switch topology query to the raw mapping, via AbstractDNSToSwitchMapping.isMappingSingleSwitch(DNSToSwitchMapping)
      Overrides:
      isSingleSwitch in class AbstractDNSToSwitchMapping
      Returns:
      true iff the raw mapper is considered single-switch.

    • reloadCachedMappings

      public void reloadCachedMappings()
      Description copied from interface: DNSToSwitchMapping
      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

      public void reloadCachedMappings(List<String> names)
      Description copied from interface: DNSToSwitchMapping
      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.