hydra

Class FixedPartitionHelper

java.lang.Object

hydra.FixedPartitionHelper

public class FixedPartitionHelper
extends Object

Helps datastores use FixedPartitionDescription. Methods are thread-safe.

Constructor Summary

Constructors

Constructor and Description
FixedPartitionHelper()

Method Summary

Modifier and Type	Method and Description
static List<com.gemstone.gemfire.cache.FixedPartitionAttributes>	assignRoundRobin(String regionName, FixedPartitionDescription fpd, int redundantCopies) Returns a list of fixed partition attributes for this JVM for the region with the specified name, or, if that is null, for the region configured in the given region description, or, if that is null, for the default region, RegionPrms.DEFAULT_REGION_NAME.

Methods inherited from class java.lang.Object

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

Constructor Detail

FixedPartitionHelper

public FixedPartitionHelper()

Method Detail

assignRoundRobin

public static List<com.gemstone.gemfire.cache.FixedPartitionAttributes> assignRoundRobin(String regionName,
                                                                                         FixedPartitionDescription fpd,
                                                                                         int redundantCopies)

Returns a list of fixed partition attributes for this JVM for the region with the specified name, or, if that is null, for the region configured in the given region description, or, if that is null, for the default region, RegionPrms.DEFAULT_REGION_NAME.

Primary and secondary partitions are assigned round robin, but in a way that prevents the same partition from being mapped to the same node twice. It constructs a list of FixedPartitionAttributes that includes the primaries and N copies of the secondaries, where N is the number of redundant copies. It then deals them out to datastores like cards. If a datastore has already been assigned a partition of the same name as the current "card", that card is skipped until an appropriate card is found. The next datastore then starts with the skipped card. An exception is thrown if it is impossible to legally deal all cards.

For example, if there are 3 datastores and 4 fixed partitions with redundancy 1, the set of assignments would look like this (bucket counts are omitted here for brevity): datastore 1: P1 primary P4 primary P3 secondary datastore 2: P2 primary P1 secondary P4 secondary datastore 3: P3 primary P2 secondary

Or, for 2 datastores and 4 fixed partitions with redundancy 1, the set of assignments would look like this: datastore 1: P1 primary P3 primary P2 secondary P4 secondary datastore 2: P2 primary P4 primary P1 secondary P3 secondary

Or, for 2 datastores and 2 fixed partitions with redundancy 2, an exception would be thrown since it is impossible to map all redundant copies to nodes that do not already contain either a primary or secondary for the same partition.

This is a suitable FixedPartitionPrms.mappingAlgorithm for most tests, tests that create the same region in multiple WAN sites. However, if the test creates multiple regions using the same logical region configuration, then it must make sure that the actual region names are passed in by invoking appropriate methods in RegionHelper.

Throws:

HydraRuntimeException - if it is impossible to map the partitions without mapping the same partition to the same datastore.