com.hazelcast.quorum.QuorumService Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2018, 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.quorum;
/**
* Quorum service can be used to trigger cluster quorums at any time.
* Normally quorums are done when any change happens on the member list.
*
* IMPORTANT: The term "quorum" simply refers to the count of members in the cluster required for an operation to succeed.
* It does NOT refer to an implementation of Paxos or Raft protocols as used in many NoSQL and distributed systems.
* The mechanism it provides in Hazelcast protects the user in case the number of nodes in a cluster drops below the
* specified one.
*/
public interface QuorumService {
/**
* Returns the {@link Quorum} instance for a given quorum name.
*
* @param quorumName name of the quorum
* @return {@link Quorum}
* @throws IllegalArgumentException if no quorum found for given name
* @throws NullPointerException if quorumName is null
*/
Quorum getQuorum(String quorumName) throws IllegalArgumentException;
/**
* Ensures that the quorum with the given name is present.
* Throws a QuorumException if quorum not present.
* Does not throw exception if quorumName null or quorum undefined.
*
* If (requiredQuorumPermissionType == READ) -> will check for presence of READ or READ_WRITE quorum
* If (requiredQuorumPermissionType == WRITE) -> will check for presence of WRITE or READ_WRITE quorum
* If (requiredQuorumPermissionType == READ_WRITE) -> will check for presence of READ_WRITE quorum
*
* @param quorumName quorum name to ensure, can be null or empty
* @param requiredQuorumPermissionType type of quorum required
* @throws QuorumException if quorum defined and not present
*/
void ensureQuorumPresent(String quorumName, QuorumType requiredQuorumPermissionType) throws QuorumException;
}