org.apache.ignite.cache.affinity.fair

Class FairAffinityFunction

java.lang.Object

org.apache.ignite.cache.affinity.fair.FairAffinityFunction

All Implemented Interfaces:

Serializable, AffinityFunction

public class FairAffinityFunction
extends Object
implements AffinityFunction

Fair affinity function which tries to ensure that all nodes get equal number of partitions with minimum amount of reassignments between existing nodes.

Cache affinity can be configured for individual caches via CacheConfiguration.setAffinity(AffinityFunction) method.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static int	DFLT_PART_CNT Default partition count.

Constructor Summary

Constructors

Constructor and Description
FairAffinityFunction() Creates fair affinity with default partition count.
FairAffinityFunction(int parts)

Method Summary

Methods

Modifier and Type	Method and Description
List<List<ClusterNode>>	assignPartitions(AffinityFunctionContext ctx) Gets affinity nodes for a partition.
int	partition(Object key) Gets partition number for a given key starting from 0.
int	partitions() Gets total number of partitions available.
void	removeNode(UUID nodeId) Removes node from affinity.
void	reset() Resets cache affinity to its initial state.

Methods inherited from class java.lang.Object

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

Field Detail

DFLT_PART_CNT

public static final int DFLT_PART_CNT

Default partition count.

See Also:

Constant Field Values

Constructor Detail

FairAffinityFunction

public FairAffinityFunction()

Creates fair affinity with default partition count.

FairAffinityFunction

public FairAffinityFunction(int parts)

Parameters:

parts - Number of partitions.

Method Detail

assignPartitions

public List<List<ClusterNode>> assignPartitions(AffinityFunctionContext ctx)

Gets affinity nodes for a partition. In case of replicated cache, all returned nodes are updated in the same manner. In case of partitioned cache, the returned list should contain only the primary and back up nodes with primary node being always first.

Note that partitioned affinity must obey the following contract: given that node N is primary for some key K, if any other node(s) leave grid and no node joins grid, node N will remain primary for key K.

Specified by:

assignPartitions in interface AffinityFunction

Parameters:

ctx - Affinity function context. Will provide all required information to calculate new partition assignments.

Returns:

Unmodifiable list indexed by partition number. Each element of array is a collection in which first node is a primary node and other nodes are backup nodes.

reset

public void reset()

Resets cache affinity to its initial state. This method will be called by the system any time the affinity has been sent to remote node where it has to be reinitialized. If your implementation of affinity function has no initialization logic, leave this method empty.

Specified by:

reset in interface AffinityFunction

partitions

public int partitions()

Gets total number of partitions available. All caches should always provide correct partition count which should be the same on all participating nodes. Note that partitions should always be numbered from 0 inclusively to N exclusively without any gaps.

Specified by:

partitions in interface AffinityFunction

Returns:

Total partition count.

partition

public int partition(Object key)

Gets partition number for a given key starting from 0. Partitioned caches should make sure that keys are about evenly distributed across all partitions from 0 to partition count for best performance.

Note that for fully replicated caches it is possible to segment key sets among different grid node groups. In that case each node group should return a unique partition number. However, unlike partitioned cache, mappings of keys to nodes in replicated caches are constant and a node cannot migrate from one partition to another.

Specified by:

partition in interface AffinityFunction

Parameters:

key - Key to get partition for.

Returns:

Partition number for a given key.

removeNode

public void removeNode(UUID nodeId)

Removes node from affinity. This method is called when it is safe to remove left node from affinity mapping.

Specified by:

removeNode in interface AffinityFunction

Parameters:

nodeId - ID of node to remove.