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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.cassandra.locator;

import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.dht.Token;


/**
 * This class returns the nodes responsible for a given
 * key but does not respect rack awareness. Basically
 * returns the RF nodes that lie right next to each other
 * on the ring.
 */
public class SimpleStrategy extends AbstractReplicationStrategy
{
    public SimpleStrategy(String keyspaceName, TokenMetadata tokenMetadata, IEndpointSnitch snitch, Map configOptions)
    {
        super(keyspaceName, tokenMetadata, snitch, configOptions);
    }

    public List calculateNaturalEndpoints(Token token, TokenMetadata metadata)
    {
        int replicas = getReplicationFactor();
        ArrayList tokens = metadata.sortedTokens();
        List endpoints = new ArrayList(replicas);

        if (tokens.isEmpty())
            return endpoints;

        // Add the token at the index by default
        Iterator iter = TokenMetadata.ringIterator(tokens, token, false);
        while (endpoints.size() < replicas && iter.hasNext())
        {
            InetAddress ep = metadata.getEndpoint(iter.next());
            if (!endpoints.contains(ep))
                endpoints.add(ep);
        }
        return endpoints;
    }

    public int getReplicationFactor()
    {
        return Integer.parseInt(this.configOptions.get("replication_factor"));
    }

    public void validateOptions() throws ConfigurationException
    {
        String rf = configOptions.get("replication_factor");
        if (rf == null)
            throw new ConfigurationException("SimpleStrategy requires a replication_factor strategy option.");
        validateReplicationFactor(rf);
    }

    public Collection recognizedOptions()
    {
        return Collections.singleton("replication_factor");
    }
}