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Advanced and thread-safe Java Redis client for synchronous, asynchronous, and reactive usage. Supports Cluster, Sentinel, Pipelining, Auto-Reconnect, Codecs and much more.

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/*
 * Copyright 2011-2016 the original author or authors.
 *
 * 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.lambdaworks.redis.cluster;

import java.util.Map;

import com.lambdaworks.redis.RedisURI;
import com.lambdaworks.redis.cluster.models.partitions.Partitions;

/**
 * Consensus API to decide on the {@link com.lambdaworks.redis.cluster.models.partitions.Partitions topology view} to be used by
 * {@link RedisClusterClient}.
 * 
 * {@link PartitionsConsensus} takes the current {@link Partitions} and a {@link java.util.Map} of newly retrieved
 * {@link Partitions} to determine a view that shall be used. Implementing classes may reuse {@link Partitions} from input
 * arguments or construct a new {@link Partitions} object.
 * 
 * @author Mark Paluch
 * @since 4.2
 * @see com.lambdaworks.redis.cluster.models.partitions.Partitions
 * @see RedisClusterClient
 */
abstract class PartitionsConsensus {

    /**
     * Consensus algorithm to select a partition containing the most previously known nodes.
     */
    public static final PartitionsConsensus KNOWN_MAJORITY = new PartitionsConsensusImpl.KnownMajority();

    /**
     * Consensus algorithm to select a topology view containing the most active nodes.
     */
    public static final PartitionsConsensus HEALTHY_MAJORITY = new PartitionsConsensusImpl.HealthyMajority();

    /**
     * Determine the {@link Partitions} to be used by {@link RedisClusterClient}.
     * 
     * @param current the currently used topology view, must not be {@literal null}.
     * @param topologyViews the newly retrieved views, must not be {@literal null}.
     * @return the resulting {@link Partitions} to be used by {@link RedisClusterClient}.
     */
    abstract Partitions getPartitions(Partitions current, Map topologyViews);
}