com.hazelcast.internal.crdt.CRDT Maven / Gradle / Ivy
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* 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.internal.crdt;
import com.hazelcast.cluster.impl.VectorClock;
/**
* Common interface for CRDT (conflict-free replicated data type)
* implementations.
* The common behaviour for all implementations is that they have a strong
* eventual consistency property - two nodes that have received the same
* set of updates, possibly in a different order, will have an identical
* shared state and any conflicting updates are merged automatically.
* All operations on the CRDT implementations are performed locally without
* any coordination with the other replicas of the same data. This allows
* for higher availability but can present data loss in some scenarios,
* e.g. the node is killed right after it receives an update. In split
* brain scenarios, each replica should keep it's local state and once the
* split brain is healed, the state of the replicas that were unreachable
* during split brain as well as the local state will converge to the same
* state.
* The CRDT state can be versioned in which case it will increase the
* version number on each mutation. This way, the replication mechanism
* will be able to replicate only those states which have not yet been
* replicated and avoid replication in a quiescent state.
*
* @param
*/
public interface CRDT> {
/**
* Merges the state of a different replica into this CRDT. The merge method
* should not leave the CRDT in a failed state.
*
* @param other the CRDT to merge into this CRDT
*/
void merge(T other);
/**
* Returns the current vector clock which reflects the current CRDT state.
*/
VectorClock getCurrentVectorClock();
}