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

@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

Fields

Modifier and Type	Field and Description
protected DNSToSwitchMapping	rawMapping The uncached mapping

Constructor Summary

Constructors

Constructor and Description
CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping) cache a raw DNS mapping

Method Summary

Methods

Modifier and Type	Method and Description
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)
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.