galileo.dht.hash

Class BalancedHashRing<T>

java.lang.Object

galileo.dht.hash.BalancedHashRing<T>

All Implemented Interfaces:

HashRing<T>

public class BalancedHashRing<T>
extends java.lang.Object
implements HashRing<T>

Creates an evenly-spaced hash ring network topology. Note that nodes in the topology are spaced evenly apart, but of course this does not guarantee the data will hash uniformly.

Author:

malensek

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.TreeMap<java.math.BigInteger,HashRingEntry>	entryMap Maps hash ring positions to ring entries
protected HashFunction<T>	function
protected java.math.BigInteger	maxHash
protected boolean	randomize If set to True, the first position in the hash ring is randomized.

Constructor Summary

Constructors

Constructor and Description
BalancedHashRing(HashFunction<T> function) Creates a BalancedHashRing using the provided hash function.
BalancedHashRing(HashFunction<T> function, boolean randomize) Creates a BalancedHashRing using the provided hash function.

Method Summary

Modifier and Type	Method and Description
java.math.BigInteger	addNode(T data) Add a node to the overlay network topology.
java.math.BigInteger	locate(T data) Determine the node that is responsible for the given data.
java.lang.String	toString() Formats the hash ring as node-to-predecessor pair Strings.

Methods inherited from class java.lang.Object

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

Field Detail

randomize

protected boolean randomize

If set to True, the first position in the hash ring is randomized.

function

protected HashFunction<T> function

maxHash

protected java.math.BigInteger maxHash

entryMap

protected java.util.TreeMap<java.math.BigInteger,HashRingEntry> entryMap

Maps hash ring positions to ring entries

Constructor Detail

BalancedHashRing

public BalancedHashRing(HashFunction<T> function)

Creates a BalancedHashRing using the provided hash function. The function will determine the size of the hash space and where nodes will be placed in the topology.

Parameters:

function - HashFunction that defines the hash space being used.

BalancedHashRing

public BalancedHashRing(HashFunction<T> function,
                        boolean randomize)

Creates a BalancedHashRing using the provided hash function. The function will determine the size of the hash space and where nodes will be placed in the topology.

Parameters:

function - HashFunction that defines the hash space being used.

Method Detail

addNode

public java.math.BigInteger addNode(T data)
                             throws HashTopologyException,
                                    HashException

Add a node to the overlay network topology.

Specified by:

addNode in interface HashRing<T>

Parameters:

data - unused for this hash ring; nodes are placed evenly based on current topology characteristics. You may safely pass 'null' to this method.

Returns:

the location of the new node in the hash space.

Throws:

HashTopologyException

HashException

locate

public java.math.BigInteger locate(T data)
                            throws HashException

Description copied from interface: HashRing

Determine the node that is responsible for the given data.

Specified by:

locate in interface HashRing<T>

Parameters:

data - the data to hash against

Returns:

identifier of the node responsible for the provided data.

Throws:

HashException

toString

public java.lang.String toString()

Formats the hash ring as node-to-predecessor pair Strings.

Overrides:

toString in class java.lang.Object

Returns:

network links and nodes in String format.