Package org.apache.hadoop.hdfs.server.federation.utils

Class ConsistentHashRing

java.lang.Object

org.apache.hadoop.hdfs.server.federation.utils.ConsistentHashRing

public class ConsistentHashRing
extends java.lang.Object

Consistent hash ring to distribute items across nodes (locations). If we add or remove nodes, it minimizes the item migration.

Constructor Summary

Constructors

Constructor	Description
ConsistentHashRing(java.util.Set<java.lang.String> locations)

Method Summary

Modifier and Type	Method	Description
void	addLocation(java.lang.String location)	Add entry to consistent hash ring.
void	addLocation(java.lang.String location, int numVirtualNodes)	Add entry to consistent hash ring.
java.lang.String	getHash(java.lang.String key)
java.lang.String	getLocation(java.lang.String item)	Return location (owner) of specified item.
java.util.Set<java.lang.String>	getLocations()	Get the locations in the ring.
void	removeLocation(java.lang.String location)	Remove specified entry from hash ring.

Methods inherited from class java.lang.Object

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

Constructor Detail

ConsistentHashRing

public ConsistentHashRing(java.util.Set<java.lang.String> locations)

Method Detail

addLocation

public void addLocation(java.lang.String location)

Add entry to consistent hash ring.

Parameters:

location - Node to add to the ring.

addLocation

public void addLocation(java.lang.String location,
                        int numVirtualNodes)

Add entry to consistent hash ring.

Parameters:

location - Node to add to the ring.

numVirtualNodes - Number of virtual nodes to add.

removeLocation

public void removeLocation(java.lang.String location)

Remove specified entry from hash ring.

Parameters:

location - Node to remove from the ring.

getLocation

public java.lang.String getLocation(java.lang.String item)

Return location (owner) of specified item. Owner is the next entry on the hash ring (with a hash value > hash value of item).

Parameters:

item - Item to look for.

Returns:

The location of the item.

getHash

public java.lang.String getHash(java.lang.String key)

getLocations

public java.util.Set<java.lang.String> getLocations()

Get the locations in the ring.

Returns:

Set of locations in the ring.