Package org.apache.hadoop.net

Class DNSDomainNameResolver

java.lang.Object

org.apache.hadoop.net.DNSDomainNameResolver

All Implemented Interfaces:

DomainNameResolver

public class DNSDomainNameResolver
extends java.lang.Object
implements DomainNameResolver

DNSDomainNameResolver wraps up the default DNS service for forward/reverse DNS lookup. It also provides a function to resolve a host name to all of fully qualified domain names belonging to the IPs from this host name

Constructor Summary

Constructors

Constructor	Description
DNSDomainNameResolver()

Method Summary

Modifier and Type	Method	Description
java.net.InetAddress[]	getAllByDomainName(java.lang.String domainName)	Takes one domain name and returns its IP addresses based on the actual service discovery methods.
java.lang.String[]	getAllResolvedHostnameByDomainName(java.lang.String domainName, boolean useFQDN)	This function combines getAllByDomainName and getHostnameByIP, for a single domain name, it will first do a forward lookup to get all of IP addresses, then for each IP address, it will do a reverse lookup to get the fqdn.
java.lang.String	getHostnameByIP(java.net.InetAddress address)	Reverse lookup an IP address and get the fully qualified domain name(fqdn).

Methods inherited from class java.lang.Object

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

Constructor Detail

DNSDomainNameResolver

public DNSDomainNameResolver()

Method Detail

getAllByDomainName

public java.net.InetAddress[] getAllByDomainName(java.lang.String domainName)
                                          throws java.net.UnknownHostException

Description copied from interface: DomainNameResolver

Takes one domain name and returns its IP addresses based on the actual service discovery methods.

Specified by:

getAllByDomainName in interface DomainNameResolver

Parameters:

domainName - input domainName.

Returns:

all IP addresses

Throws:

java.net.UnknownHostException - indicate that the IP address of a host could not be determined.

getHostnameByIP

public java.lang.String getHostnameByIP(java.net.InetAddress address)

Description copied from interface: DomainNameResolver

Reverse lookup an IP address and get the fully qualified domain name(fqdn).

Specified by:

getHostnameByIP in interface DomainNameResolver

Parameters:

address - input address.

Returns:

fully qualified domain name

getAllResolvedHostnameByDomainName

public java.lang.String[] getAllResolvedHostnameByDomainName(java.lang.String domainName,
                                                             boolean useFQDN)
                                                      throws java.net.UnknownHostException

Description copied from interface: DomainNameResolver

This function combines getAllByDomainName and getHostnameByIP, for a single domain name, it will first do a forward lookup to get all of IP addresses, then for each IP address, it will do a reverse lookup to get the fqdn. This function is necessary in secure environment since Kerberos uses fqdn in the service principal instead of IP.

Specified by:

getAllResolvedHostnameByDomainName in interface DomainNameResolver

Parameters:

domainName - input domainName.

useFQDN - input useFQDN.

Returns:

all fully qualified domain names belonging to the IPs resolved from the input domainName

Throws:

java.net.UnknownHostException - indicate that the IP address of a host could not be determined.