Package org.apache.hadoop.net

Interface DomainNameResolver

All Known Implementing Classes:

DNSDomainNameResolver

public interface DomainNameResolver

This interface provides methods for the failover proxy to get IP addresses of the associated servers (NameNodes, RBF routers etc). Implementations will use their own service discovery mechanism, DNS, Zookeeper etc

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).

Method Detail

getAllByDomainName

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

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

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

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

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

Parameters:

address - input address.

Returns:

fully qualified domain name

getAllResolvedHostnameByDomainName

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

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.

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.