org.apache.ignite.igfs

Class IgfsGroupDataBlocksKeyMapper

java.lang.Object

org.apache.ignite.internal.processors.cache.GridCacheDefaultAffinityKeyMapper

org.apache.ignite.igfs.IgfsGroupDataBlocksKeyMapper

All Implemented Interfaces:

Serializable, AffinityKeyMapper

public class IgfsGroupDataBlocksKeyMapper
extends GridCacheDefaultAffinityKeyMapper

IGFS class providing ability to group file's data blocks together on one node. All blocks within the same group are guaranteed to be cached together on the same node. Group size parameter controls how many sequential blocks will be cached together on the same node.

For example, if block size is 64kb and group size is 256, then each group will contain 64kb * 256 = 16Mb. Larger group sizes would reduce number of splits required to run map-reduce tasks, but will increase inequality of data size being stored on different nodes.

Note that groupSize() parameter must correlate to Hadoop split size parameter defined in Hadoop via mapred.max.split.size property. Ideally you want all blocks accessed within one split to be mapped to 1 group, so they can be located on the same grid node. For example, default Hadoop split size is 64mb and default IGFS block size is 64kb. This means that to make sure that each split goes only through blocks on the same node (without hopping between nodes over network), we have to make the groupSize() value be equal to 64mb / 64kb = 1024.

It is required for IGFS data cache to be configured with this mapper. Here is an example of how it can be specified in XML configuration:

 <bean id="cacheCfgBase" class="org.apache.ignite.cache.CacheConfiguration" abstract="true">
     ...
     <property name="affinityMapper">
         <bean class="org.apache.ignite.igfs.IgfsGroupDataBlocksKeyMapper">
             <!-- How many sequential blocks will be stored on the same node. -->
             <constructor-arg value="512"/>
         </bean>
     </property>
     ...
 </bean>
 

See Also:

Serialized Form

Field Summary

Fields inherited from class org.apache.ignite.internal.processors.cache.GridCacheDefaultAffinityKeyMapper

ignite, log

Constructor Summary

Constructors

Constructor and Description
IgfsGroupDataBlocksKeyMapper(int grpSize) Constructs affinity mapper to group several data blocks with the same key.

Method Summary

Methods

Modifier and Type	Method and Description
Object	affinityKey(Object key) If key class has annotation AffinityKeyMapped, then the value of annotated method or field will be used to get affinity value instead of the key itself.
int	groupSize()
String	toString()

Methods inherited from class org.apache.ignite.internal.processors.cache.GridCacheDefaultAffinityKeyMapper

ignite, reset

Methods inherited from class java.lang.Object

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

Constructor Detail

IgfsGroupDataBlocksKeyMapper

public IgfsGroupDataBlocksKeyMapper(int grpSize)

Constructs affinity mapper to group several data blocks with the same key.

Parameters:

grpSize - Size of the group in blocks.

Method Detail

affinityKey

public Object affinityKey(Object key)

If key class has annotation AffinityKeyMapped, then the value of annotated method or field will be used to get affinity value instead of the key itself. If there is no annotation, then the key is returned as is.

Specified by:

affinityKey in interface AffinityKeyMapper

Overrides:

affinityKey in class GridCacheDefaultAffinityKeyMapper

Parameters:

key - Key to get affinity key for.

Returns:

Affinity key for given key.

groupSize

public int groupSize()

Returns:

Size of the group.

toString

public String toString()

Overrides:

toString in class Object