org.infinispan.distribution
Class UnionConsistentHash

java.lang.Object
  extended by org.infinispan.distribution.AbstractConsistentHash
      extended by org.infinispan.distribution.UnionConsistentHash
All Implemented Interfaces:
ConsistentHash

public class UnionConsistentHash
extends AbstractConsistentHash

A delegating wrapper that locates keys by getting a union of locations reported by two other ConsistentHash implementations it delegates to.

Since:
4.0
Author:
Manik Surtani

Nested Class Summary
static class UnionConsistentHash.Externalizer
           
 
Constructor Summary
UnionConsistentHash(ConsistentHash oldCH, ConsistentHash newCH)
           
 
Method Summary
 List<Address> getCaches()
          Should return a collection of cache addresses in the cluster.
 int getDistance(Address a1, Address a2)
          Calculates the logical distance between two addresses.
 int getHashId(Address a)
          Returns the value between 0 and the hash space limit, or hash id, for a particular address.
 int getHashSpace()
          Returns the hash space constant for this consistent hash algorithm class.
 ConsistentHash getNewConsistentHash()
           
 ConsistentHash getOldConsistentHash()
           
 boolean isAdjacent(Address a1, Address a2)
          Tests whether two addresses are logically next to each other in the hash space.
 List<Address> locate(Object key, int replCount)
          Locates a key, given a replication count (number of copies).
 void setCaches(List<Address> caches)
          Sets the collection of cache addresses in the cluster.
 
Methods inherited from class org.infinispan.distribution.AbstractConsistentHash
isKeyLocalToAddress, locateAll
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

UnionConsistentHash

public UnionConsistentHash(ConsistentHash oldCH,
                           ConsistentHash newCH)
Method Detail

setCaches

public void setCaches(List<Address> caches)
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:
caches - caches in cluster.

getCaches

public List<Address> getCaches()
Description copied from interface: ConsistentHash
Should return a collection of cache addresses in the cluster.

Returns:
collection of cache addresses

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.List). Should never be null, and should contain replCount elements or the max number of caches available, whichever is smaller.

getDistance

public int getDistance(Address a1,
                       Address a2)
Description copied from interface: ConsistentHash
Calculates the logical distance between two addresses. This distance is based on where the addresses lie in the hash space.

Parameters:
a1 - address to test
a2 - address to test
Returns:
the distance between the 2 nodes. Always a positive number, where the distance between a1 and itself is 0. The distance between a1 and the next adjacent node is 1 and teh distance between a1 and the previous adjacent node is caches.size() - 1. A -1 may be returned if either of the addresses do not exist.

isAdjacent

public boolean isAdjacent(Address a1,
                          Address a2)
Description copied from interface: ConsistentHash
Tests whether two addresses are logically next to each other in the hash space.

Parameters:
a1 - address to test
a2 - address to test
Returns:
true if adjacent, false if not

getHashId

public int getHashId(Address a)
Description copied from interface: ConsistentHash
Returns the value between 0 and the hash space limit, or hash id, for a particular address. If there's no such value for an address, this method will return -1.

Returns:
An int between 0 and hash space if the address is present in the hash wheel, otherwise it returns -1.

getHashSpace

public int getHashSpace()
Description copied from interface: ConsistentHash
Returns the hash space constant for this consistent hash algorithm class. This integer is often used as modulus for arithmetic operations within the algorithm, for example, limiting the range of possible hash values.

Returns:
A positive integer containing the hash space constant or 0 is not supported by implementation.

getNewConsistentHash

public ConsistentHash getNewConsistentHash()

getOldConsistentHash

public ConsistentHash getOldConsistentHash()

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