storm-client/src/jvm/org/apache/storm/testing/AlternateRackDNSToSwitchMapping.java

/**
 * 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.storm.testing;

import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.storm.networktopography.AbstractDNSToSwitchMapping;
import org.apache.storm.networktopography.DNSToSwitchMapping;

/**
 * This class implements the {@link DNSToSwitchMapping} interface It alternates bewteen RACK1 and RACK2 for the hosts.
 */
@SuppressWarnings("checkstyle:AbbreviationAsWordInName")
public final class AlternateRackDNSToSwitchMapping extends AbstractDNSToSwitchMapping {

    private Map<String, String> mappingCache = new ConcurrentHashMap<String, String>();

    @Override
    public Map<String, String> resolve(List<String> names) {
        TreeSet<String> sortedNames = new TreeSet<String>(names);
        Map<String, String> m = new HashMap<String, String>();
        if (names.isEmpty()) {
            //name list is empty, return an empty map
            return m;
        }

        Boolean odd = true;
        for (String name : sortedNames) {
            if (odd) {
                m.put(name, "RACK1");
                mappingCache.put(name, "RACK1");
                odd = false;
            } else {
                m.put(name, "RACK2");
                mappingCache.put(name, "RACK2");
                odd = true;
            }
        }
        return m;
    }

    @Override
    public String toString() {
        return "defaultRackDNSToSwitchMapping (" + mappingCache.size() + " mappings cached)";
    }
}