org.infinispan.distribution.ch
Class TopologyAwareConsistentHash

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

All Implemented Interfaces:

ConsistentHash

public class TopologyAwareConsistentHash
extends AbstractWheelConsistentHash

Consistent hash that is aware of cluster topology. Design described here: http://community.jboss.org/wiki/DesigningServerHinting.

 Algorithm:
 - place nodes on the hash wheel based address's hash code
 - For selecting owner nodes:
       - pick the first one based on key's hash code
       - for subsequent nodes, walk clockwise and pick nodes that have a different site id
       - if not enough nodes found repeat walk again and pick nodes that have different site id and rack id
       - if not enough nodes found repeat walk again and pick nodes that have different site id, rack id and machine
 id
       - Ultimately cycle back to the first node selected, don't discard any nodes, regardless of machine id/rack
 id/site id match.
 

Since:

4.2

Author:

Mircea.Markus@jboss.com

Nested Class Summary

static class

TopologyAwareConsistentHash.Externalizer

Field Summary

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

caches, hashFunction, numVirtualNodes, positionKeys, positionValues, trace

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

groupManager

Constructor Summary

TopologyAwareConsistentHash()

TopologyAwareConsistentHash(Hash hash)

Method Summary

protected Log	getLog()
boolean	isKeyLocalToAddress(Address target, Object key, int replCount) Test to see whether a key is mapped to a given address.
List<Address>	locate(Object key, int replCount) Locates a key, given a replication count (number of copies).
void	setCaches(Set<Address> newCaches) Sets the collection of cache addresses in the cluster.

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

getCaches, getHashIds, getNormalizedHash, getPositionIndex, getPositionsIterator, isVirtualNodesEnabled, primaryLocation, setHashFunction, setNumVirtualNodes, toString

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

getBackupsForNode, getGrouping, getStateProvidersOnJoin, getStateProvidersOnLeave, locateAll, setGroupManager

Methods inherited from class java.lang.Object

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

Constructor Detail

TopologyAwareConsistentHash

public TopologyAwareConsistentHash()

TopologyAwareConsistentHash

public TopologyAwareConsistentHash(Hash hash)

Method Detail

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.

Specified by:

setCaches in interface ConsistentHash

Overrides:

setCaches in class AbstractWheelConsistentHash

Parameters:

newCaches - A set of unique caches in cluster.

locate

public List<Address> locate(Object key,
                            int replCount)

Description copied from interface: ConsistentHash

Locates a key, given a replication count (number of copies).

Parameters:

key - key to locate

replCount - replication count (number of copies)

Returns:

a list of addresses where the key resides, where this list is a subset of the addresses set in ConsistentHash.setCaches(java.util.Set). Should never be null, and should contain replCount elements or the max number of caches available, whichever is smaller.

isKeyLocalToAddress

public boolean isKeyLocalToAddress(Address target,
                                   Object key,
                                   int replCount)

Description copied from interface: ConsistentHash

Test to see whether a key is mapped to a given address.

Specified by:

isKeyLocalToAddress in interface ConsistentHash

Overrides:

isKeyLocalToAddress in class AbstractConsistentHash

Parameters:

target - address to test

key - key to test

replCount - repl count

Returns:

true if the key is mapped to the address; false otherwise

getLog

protected Log getLog()

Overrides:

getLog in class AbstractWheelConsistentHash