Interface IAffinityFunction

Represents a function that maps cache keys to cluster nodes.

Predefined implementations: RendezvousAffinityFunction.

Namespace: Apache.Ignite.Core.Cache.Affinity

Assembly: Apache.Ignite.Core.dll

Syntax

public interface IAffinityFunction

Properties

Partitions

Gets the total number of partitions.

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.

Declaration

int Partitions { get; }

Property Value

Type	Description
System.Int32

Methods

AssignPartitions(AffinityFunctionContext)

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

.

Declaration

IEnumerable<IEnumerable<IClusterNode>> AssignPartitions(AffinityFunctionContext context)

Parameters

Type	Name	Description
AffinityFunctionContext	context	The affinity function context.

Returns

Type	Description
IEnumerable<IEnumerable<IClusterNode>>	A collection of partitions, where each partition is a collection of nodes, where first node is a primary node, and other nodes are backup nodes.

GetPartition(Object)

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 Partitions 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.

Declaration

int GetPartition(object key)

Parameters

Type	Name	Description
System.Object	key	Key to get partition for.

Returns

Type	Description
System.Int32	Partition number for a given key.

RemoveNode(Guid)

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

Declaration

void RemoveNode(Guid nodeId)

Parameters

Type	Name	Description
Guid	nodeId	The node identifier.