org.infinispan.distribution.ch
Class AbstractWheelConsistentHash

java.lang.Object
  org.infinispan.distribution.ch.AbstractConsistentHash
      org.infinispan.distribution.ch.AbstractWheelConsistentHash

All Implemented Interfaces:

ConsistentHash

Direct Known Subclasses:

DefaultConsistentHash, TopologyAwareConsistentHash

public abstract class AbstractWheelConsistentHash
extends AbstractConsistentHash

Abstract class for the wheel-based CH implementations.

This base class supports virtual nodes. To enable virtual nodes you must set numVirtualNodes to a number > 1.

Enabling virtual nodes means that a cache will appear multiple times on the hash wheel. If an implementation doesn't want to support this, it should override setNumVirtualNodes(Integer) to throw an IllegalArgumentException for values != 1.

Since:

4.2

Author:

Mircea.Markus@jboss.com, Pete Muir, Dan Berindei

Nested Class Summary

static class

AbstractWheelConsistentHash.Externalizer<T extends AbstractWheelConsistentHash>

Field Summary

protected Set<Address>	caches
protected Hash	hashFunction
protected Log	log
protected int	numVirtualNodes
protected int[]	positionKeys
protected Address[]	positionValues
protected boolean	trace

Fields inherited from class org.infinispan.distribution.ch.AbstractConsistentHash

groupManager

Constructor Summary

protected

AbstractWheelConsistentHash()

Method Summary

Set<Address>	getCaches() Should return a collection of cache addresses in the cluster.
List<Integer>	getHashIds(Address a) Returns a list of values between 0 and the hash space limit, or hash id, for a particular address.
int	getNormalizedHash(Object key)
protected int	getPositionIndex(int normalizedHash)
protected Iterator<Map.Entry<Integer,Address>>	getPositionsIterator(int normalizedHash) Creates an iterator over the positions "map" starting at the index specified by the normalizedHash.
protected boolean	isVirtualNodesEnabled()
void	setCaches(Set<Address> newCaches) Sets the collection of cache addresses in the cluster.
void	setHashFunction(Hash h)
void	setNumVirtualNodes(Integer numVirtualNodes)
String	toString()

Methods inherited from class org.infinispan.distribution.ch.AbstractConsistentHash

getBackupsForNode, getGrouping, getStateProvidersOnJoin, getStateProvidersOnLeave, isKeyLocalToAddress, locateAll, setGroupManager

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.infinispan.distribution.ch.ConsistentHash

locate

Field Detail

log

protected final Log log

trace

protected final boolean trace

hashFunction

protected Hash hashFunction

numVirtualNodes

protected int numVirtualNodes

caches

protected Set<Address> caches

positionKeys

protected int[] positionKeys

positionValues

protected Address[] positionValues

Constructor Detail

AbstractWheelConsistentHash

protected AbstractWheelConsistentHash()

Method Detail

setHashFunction

public void setHashFunction(Hash h)

setNumVirtualNodes

public void setNumVirtualNodes(Integer numVirtualNodes)

setCaches

public void setCaches(Set<Address> newCaches)

Description copied from interface: ConsistentHash

Sets the collection of cache addresses in the cluster. The implementation should store these internally and use these to locate keys.

Parameters:

newCaches - A set of unique caches in cluster.

getCaches

public Set<Address> getCaches()

Description copied from interface: ConsistentHash

Should return a collection of cache addresses in the cluster.

Returns:

set of unique of cache addresses

getPositionIndex

protected int getPositionIndex(int normalizedHash)

getPositionsIterator

protected Iterator<Map.Entry<Integer,Address>> getPositionsIterator(int normalizedHash)

Creates an iterator over the positions "map" starting at the index specified by the normalizedHash.

getHashIds

public List<Integer> getHashIds(Address a)

Description copied from interface: ConsistentHash

Returns a list of values between 0 and the hash space limit, or hash id, for a particular address. If virtual nodes are disabled, the list will only contain a single element, whereas if virtual nodes are enabled, this list's size will be the number of virtual nodes configured. If there are no hash ids for that address, it returns an empty list.

Returns:

A list of N size where N is the configured number of virtual nodes, or an empty list if there're no hash ids associated with the address.

getNormalizedHash

public int getNormalizedHash(Object key)

isVirtualNodesEnabled

protected boolean isVirtualNodesEnabled()

toString

public String toString()

Overrides:

toString in class AbstractConsistentHash