org.infinispan.distribution.ch
Interface ConsistentHash

All Known Implementing Classes:
AbstractConsistentHash, AbstractWheelConsistentHash, DefaultConsistentHash, ExperimentalDefaultConsistentHash, TopologyAwareConsistentHash, UnionConsistentHash

public interface ConsistentHash

A consistent hash algorithm implementation. Implementations would typically be constructed via reflection so should implement a public, no-arg constructor.

Since:
4.0
Author:
Manik Surtani, Mircea.Markus@jboss.com

Method Summary
 List<Address> getBackupsForNode(Address node, int replCount)
          Returns the nodes that backup data for the supplied node including the node itself.
 Set<Address> getCaches()
          Should return a collection of cache addresses in the cluster.
 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.
 List<Address> getStateProvidersOnJoin(Address joiner, int replCount)
          Returns the nodes that would act as state providers when a new node joins: - the nodes for which the joiner is a backup - the nodes that held joiner's state
 List<Address> getStateProvidersOnLeave(Address leaver, int replCount)
          Returns the nodes that need will replicate their state if the specified node crashes.
 boolean isKeyLocalToAddress(Address a, 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).
 Map<Object,List<Address>> locateAll(Collection<Object> keys, int replCount)
          The logical equivalent of calling locate(Object, int) multiple times for each key in the collection of keys.
 void setCaches(Set<Address> caches)
          Sets the collection of cache addresses in the cluster.
 void setTopologyInfo(TopologyInfo topologyInfo)
          Sets cluster topology information that can be used by CH to improve fault tolerance by smart choosing of backups.
 

Method Detail

setCaches

void setCaches(Set<Address> caches)
Sets the collection of cache addresses in the cluster. The implementation should store these internally and use these to locate keys.

Parameters:
caches - A set of unique caches in cluster.

setTopologyInfo

void setTopologyInfo(TopologyInfo topologyInfo)
Sets cluster topology information that can be used by CH to improve fault tolerance by smart choosing of backups. More about it here


getCaches

Set<Address> getCaches()
Should return a collection of cache addresses in the cluster.

Returns:
set of unique of cache addresses

locate

List<Address> locate(Object key,
                     int replCount)
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 setCaches(java.util.Set). Should never be null, and should contain replCount elements or the max number of caches available, whichever is smaller.

locateAll

Map<Object,List<Address>> locateAll(Collection<Object> keys,
                                    int replCount)
The logical equivalent of calling locate(Object, int) multiple times for each key in the collection of keys. Implementations may be optimised for such a bulk lookup, or may just repeatedly call locate(Object, int).

Parameters:
keys - keys to locate
replCount - replication count (number of copies) for each key
Returns:
Map of locations, keyed on key.

isKeyLocalToAddress

boolean isKeyLocalToAddress(Address a,
                            Object key,
                            int replCount)
Test to see whether a key is mapped to a given address.

Parameters:
a - address to test
key - key to test
replCount - repl count
Returns:
true if the key is mapped to the address; false otherwise

getHashId

int getHashId(Address a)
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

int getHashSpace()
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.

getStateProvidersOnLeave

List<Address> getStateProvidersOnLeave(Address leaver,
                                       int replCount)
Returns the nodes that need will replicate their state if the specified node crashes. The return collection should contain all the nodes that backup-ed on leaver and one of the nodes which acted as a backup for the leaver .

Pre: leaver must be present in the caches known to this CH, as returned by getCaches()

Parameters:
leaver - the node that leaves the cluster
replCount -

getStateProvidersOnJoin

List<Address> getStateProvidersOnJoin(Address joiner,
                                      int replCount)
Returns the nodes that would act as state providers when a new node joins: - the nodes for which the joiner is a backup - the nodes that held joiner's state


getBackupsForNode

List<Address> getBackupsForNode(Address node,
                                int replCount)
Returns the nodes that backup data for the supplied node including the node itself.



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