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

Nested Classes

Modifier and Type	Class and Description
static class	AbstractWheelConsistentHash.Externalizer<T extends AbstractWheelConsistentHash>

Field Summary

Fields

Modifier and Type	Field and Description
protected Set<Address>	caches
protected Hash	hashFunction
protected int	numVirtualNodes
protected int[]	positionKeys
protected Address[]	positionValues
protected boolean	trace

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

groupManager

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractWheelConsistentHash()

Method Summary

Methods

Modifier and Type	Method and Description
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.
protected Log	getLog()
int	getNormalizedHash(Object key)
protected int	getPositionIndex(int normalizedHash)
protected Iterator<Address>	getPositionsIterator(int normalizedHash) Creates an iterator over the positions "map" starting at the index specified by the normalizedHash.
boolean	isVirtualNodesEnabled()
Address	primaryLocation(Object key) Should be equivalent to return the first element of ConsistentHash.locate(Object, int).
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

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 final 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 final int getPositionIndex(int normalizedHash)

getPositionsIterator

protected final Iterator<Address> getPositionsIterator(int normalizedHash)

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

getHashIds

public final 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 final int getNormalizedHash(Object key)

isVirtualNodesEnabled

public final boolean isVirtualNodesEnabled()

toString

public String toString()

Overrides:

toString in class AbstractConsistentHash

primaryLocation

public final Address primaryLocation(Object key)

Description copied from interface: ConsistentHash

Should be equivalent to return the first element of ConsistentHash.locate(Object, int). Useful as a performance optimization, as this is a frequently needed information.

Specified by:

primaryLocation in interface ConsistentHash

Overrides:

primaryLocation in class AbstractConsistentHash

Parameters:

key - key to locate

Returns:

getLog

protected Log getLog()