    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    }