org.forgerock.opendj.ldap

Class ConsistentHashMap<P>

java.lang.Object

org.forgerock.opendj.ldap.ConsistentHashMap<P>

Type Parameters:

P - The type of partition object.

public final class ConsistentHashMap<P>
extends Object

An implementation of "consistent hashing" supporting per-partition weighting. This implementation is thread safe and allows partitions to be added and removed during use.

This implementation maps partitions to one or more points on a circle ranging from Integer.MIN_VALUE to Integer.MAX_VALUE. The number of points per partition is dictated by the partition's weight. A partition with a weight which is higher than another partition will receive a proportionally higher load.

See Also:

Consistent Hashing and Random Trees, Web Caching with Consistent Hashing

Constructor Summary

Constructors

Constructor and Description
ConsistentHashMap() Creates a new consistent hash map which will hash keys using MD5.
ConsistentHashMap(org.forgerock.util.Function<Object,Integer,org.forgerock.util.promise.NeverThrowsException> hashFunction) Creates a new consistent hash map which will hash keys using the provided hash function.

Method Summary

Modifier and Type	Method and Description
ConsistentHashMap<P>	put(String partitionId, P partition) Puts a partition into this consistent hash map using the default weight which is sufficiently high to ensure a reasonably uniform distribution among all partitions having the same weight.
ConsistentHashMap<P>	put(String partitionId, P partition, int weight) Puts a partition into this consistent hash map using the specified weight.
ConsistentHashMap<P>	remove(String partitionId) Removes the partition that was previously added using the provided partition ID.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

ConsistentHashMap

public ConsistentHashMap()

Creates a new consistent hash map which will hash keys using MD5.

ConsistentHashMap

public ConsistentHashMap(org.forgerock.util.Function<Object,Integer,org.forgerock.util.promise.NeverThrowsException> hashFunction)

Creates a new consistent hash map which will hash keys using the provided hash function.

Parameters:

hashFunction - The function which should be used for hashing keys.

Method Detail

put

public ConsistentHashMap<P> put(String partitionId,
                                P partition)

Puts a partition into this consistent hash map using the default weight which is sufficiently high to ensure a reasonably uniform distribution among all partitions having the same weight.

Parameters:

partitionId - The partition ID.

partition - The partition.

Returns:

This consistent hash map.

put

public ConsistentHashMap<P> put(String partitionId,
                                P partition,
                                int weight)

Puts a partition into this consistent hash map using the specified weight. If all partitions have the same weight then they will each receive a similar amount of load. A partition having a weight which is twice that of another will receive twice the load. Weight values should generally be great than 200 in order to minimize the risk of unexpected imbalances due to the way in which logical partitions are mapped to real partitions.

Parameters:

partitionId - The partition ID.

partition - The partition.

weight - The partition's weight, which should typically be over 200 and never negative.

Returns:

This consistent hash map.

remove

public ConsistentHashMap<P> remove(String partitionId)

Removes the partition that was previously added using the provided partition ID.

Parameters:

partitionId - The partition ID.

Returns:

This consistent hash map.

toString

public String toString()

Overrides:

toString in class Object