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# Class AffinityFunctionBase

Base class for predefined affinity functions.

##### Inheritance

System.Object
AffinityFunctionBase
RendezvousAffinityFunction

##### Implements

IAffinityFunction

###### Namespace: Apache.Ignite.Core.Cache.Affinity

###### Assembly: Apache.Ignite.Core.dll

##### Syntax

    public abstract class AffinityFunctionBase : object, IAffinityFunction

### Fields

#### DefaultPartitions

The default value for Partitions property.

##### Declaration

    public const int DefaultPartitions = null

##### Field Value

Type | Description
--- | ---
System.Int32 |

### Properties

#### ExcludeNeighbors

Gets or sets a value indicating whether to exclude same-host-neighbors from being backups of each other.

##### Declaration

    public virtual bool ExcludeNeighbors { get; set; }

##### Property Value

Type | Description
--- | ---
System.Boolean |

#### Partitions

Gets or sets the total number of partitions.

##### Declaration

    public virtual int Partitions { get; set; }

##### 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

    public virtual 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

    public virtual 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

    public virtual void RemoveNode(Guid nodeId)

##### Parameters

Type | Name | Description
--- | --- | ---
Guid | nodeId | The node identifier.

### Implements

IAffinityFunction