Interface SplitBrainMergePolicy<V,T extends MergingValue<V>,R>
- Type Parameters:
V
- the (deserialized) type of the merging valueT
- the type of the required merging value, e.g. a simpleMergingValue<V>
or a composition likeMergingEntry<String, V> & MergingHits & MergingLastAccessTime
R
- the type of the merged value as returned bymerge(MergingValue, MergingValue)
- All Superinterfaces:
DataSerializable
- All Known Implementing Classes:
com.hazelcast.spi.impl.merge.AbstractSplitBrainMergePolicy
,DiscardMergePolicy
,ExpirationTimeMergePolicy
,HigherHitsMergePolicy
,HyperLogLogMergePolicy
,LatestAccessMergePolicy
,LatestUpdateMergePolicy
,PassThroughMergePolicy
,PutIfAbsentMergePolicy
The values of merging and existing MergingValue
s are
always in the in-memory format of the backing data structure.
This can be a serialized format, so the content cannot be
processed without deserialization. For most merge policies
this will be fine, since the key or value are not used.
The deserialization is not done eagerly for two main reasons:
- The deserialization is quite expensive and should be avoided, if the result is not needed.
- There is no need to locate classes of stored entries
on the server side, when the entries are not deserialized.
So you can put entries from a client by using
InMemoryFormat.BINARY
with a different classpath on client and server. In this case a deserialization could throw aClassNotFoundException
.
MergingValue.getDeserializedValue()
or MergingEntry.getKey()
,
which will deserialize the data lazily.
A merge policy can implement HazelcastInstanceAware
to get the
HazelcastInstance
injected. This can be used to retrieve the
user context via HazelcastInstance.getUserContext()
, which is
an easy way to get user dependencies that are otherwise hard to obtain.
A merge policy can also implement NodeAware
to get an instance of Node
injected.
- Since:
- 3.10
-
Method Summary
Modifier and TypeMethodDescriptionSelects the value of either the merging or the existingMergingValue
which should be merged.Methods inherited from interface com.hazelcast.nio.serialization.DataSerializable
readData, writeData
-
Method Details
-
merge
Selects the value of either the merging or the existingMergingValue
which should be merged.Note that the existing
MergingValue
instance may benull
if no matching data could be found to the mergingMergingValue
.- Parameters:
mergingValue
-MergingValue
instance that has the merging data of the smaller sub-clusterexistingValue
-MergingValue
instance that has the existing data ornull
if no matching data exists- Returns:
- the selected value for merging
-