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

@InterfaceAudience.Public
@InterfaceStability.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 Summary

protected DNSToSwitchMapping

rawMapping The uncached mapping

Constructor Summary

CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping)
cache a raw DNS mapping

Method Summary

Map<String,String>	getSwitchMap() Get the (host x switch) map.
boolean	isSingleSwitch() Delegate the switch topology query to the raw mapping, via AbstractDNSToSwitchMapping.isMappingSingleSwitch(DNSToSwitchMapping)
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).
String	toString()

Methods inherited from class org.apache.hadoop.net.AbstractDNSToSwitchMapping

dumpTopology, getConf, isMappingSingleSwitch, isSingleSwitchByScriptPolicy, setConf

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

rawMapping

protected final DNSToSwitchMapping rawMapping

The uncached mapping

Constructor Detail

CachedDNSToSwitchMapping

public CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping)

cache a raw DNS mapping

Parameters:

rawMapping - the raw mapping to cache

Method Detail

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.