001    /*
002     * Copyright 2009 Red Hat, Inc.
003     * Red Hat licenses this file to you under the Apache License, version
004     * 2.0 (the "License"); you may not use this file except in compliance
005     * with the License.  You may obtain a copy of the License at
006     *    http://www.apache.org/licenses/LICENSE-2.0
007     * Unless required by applicable law or agreed to in writing, software
008     * distributed under the License is distributed on an "AS IS" BASIS,
009     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
010     * implied.  See the License for the specific language governing
011     * permissions and limitations under the License.
012     */
013    
014    package org.hornetq.api.core.client.loadbalance;
015    
016    import org.hornetq.utils.Random;
017    
018    import java.io.Serializable;
019    
020    /**
021     * RoundRobinConnectionLoadBalancingPolicy corresponds to a round-robin load-balancing policy.
022     * 
023     * <br>
024     * The first call to {@link #select(int)} will return a random integer between {@code 0} (inclusive) and {@code max} (exclusive).
025     * Subsequent calls will then return an integer in a round-robin fashion.
026     *
027     * @author <a href="mailto:tim.fox@jboss.com">Tim Fox</a>
028     * 
029     * Created 28 Nov 2008 10:21:08
030     *
031     *
032     */
033    public class RoundRobinConnectionLoadBalancingPolicy implements ConnectionLoadBalancingPolicy, Serializable
034    {
035       private static final long serialVersionUID = 7511196010141439559L;
036    
037       private final Random random = new Random();
038    
039       private boolean first = true;
040    
041       private int pos;
042    
043       public int select(final int max)
044       {
045          if (first)
046          {
047             // We start on a random one
048             pos = random.getRandom().nextInt(max);
049    
050             first = false;
051          }
052          else
053          {
054             pos++;
055    
056             if (pos >= max)
057             {
058                pos = 0;
059             }
060          }
061    
062          return pos;
063       }
064    }