com.hazelcast.replicatedmap.merge.ReplicatedMapMergePolicy Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2020, Hazelcast, Inc. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.replicatedmap.merge;
import com.hazelcast.replicatedmap.impl.record.ReplicatedMapEntryView;
import java.io.Serializable;
/**
* Policy for merging replicated map entries after a split-brain has been healed.
*
* @see com.hazelcast.replicatedmap.merge.HigherHitsMapMergePolicy
* @see com.hazelcast.replicatedmap.merge.LatestUpdateMapMergePolicy
* @see com.hazelcast.replicatedmap.merge.PassThroughMergePolicy
* @see com.hazelcast.replicatedmap.merge.PutIfAbsentMapMergePolicy
*/
public interface ReplicatedMapMergePolicy extends Serializable {
/**
* Selects one of the merging and existing map entries to be merged.
*
* Note that the {@code existingEntry} may be {@code null} if there
* is no entry with the same key in the destination map.
* This happens, when the entry for that key was
*
* - only created in the smaller sub-cluster during the split-brain
* - removed in the larger sub-cluster during the split-brain
*
*
* @param mapName name of the replicated map
* @param mergingEntry {@link ReplicatedMapEntryView} instance that has the map entry to be merged
* @param existingEntry {@link ReplicatedMapEntryView} instance that has the existing map entry
* or {@code null} if there is no existing map entry
* @return the selected value for merging or {@code null} if the entry should be removed
*/
Object merge(String mapName, ReplicatedMapEntryView mergingEntry, ReplicatedMapEntryView existingEntry);
}