KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > jboss > ha > framework > interfaces > RoundRobin


1 /*
2   * JBoss, Home of Professional Open Source
3   * Copyright 2005, JBoss Inc., and individual contributors as indicated
4   * by the @authors tag. See the copyright.txt in the distribution for a
5   * full listing of individual contributors.
6   *
7   * This is free software; you can redistribute it and/or modify it
8   * under the terms of the GNU Lesser General Public License as
9   * published by the Free Software Foundation; either version 2.1 of
10   * the License, or (at your option) any later version.
11   *
12   * This software is distributed in the hope that it will be useful,
13   * but WITHOUT ANY WARRANTY; without even the implied warranty of
14   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15   * Lesser General Public License for more details.
16   *
17   * You should have received a copy of the GNU Lesser General Public
18   * License along with this software; if not, write to the Free
19   * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20   * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21   */
22 package org.jboss.ha.framework.interfaces;
23
24 import java.util.List JavaDoc;
25
26 import org.jboss.invocation.Invocation;
27
28 /**
29  * LoadBalancingPolicy implementation that always favor the next available
30  * target load balancing always occurs.
31  *
32  * @see org.jboss.ha.framework.interfaces.LoadBalancePolicy
33  *
34  * @author <a HREF="mailto:sacha.labourey@cogito-info.ch">Sacha Labourey</a>.
35  * @author <a HREF="mailto:bill@burkecentral.com">Bill Burke</a>.
36  * @version $Revision: 56192 $
37  */
38 public class RoundRobin implements LoadBalancePolicy
39 {
40    // Constants -----------------------------------------------------
41 /** @since 1.3.4.2 */
42    private static final long serialVersionUID = 8660076707279597114L;
43
44    // Attributes ----------------------------------------------------
45
46    // Static --------------------------------------------------------
47
48    // Constructors --------------------------------------------------
49
50    // Public --------------------------------------------------------
51
52    public void init (HARMIClient father)
53    {
54       // do not use the HARMIClient in this policy
55 }
56
57    public Object JavaDoc chooseTarget (FamilyClusterInfo clusterFamily)
58    {
59       return this.chooseTarget(clusterFamily, null);
60    }
61    public Object JavaDoc chooseTarget (FamilyClusterInfo clusterFamily, Invocation routingDecision)
62    {
63       int cursor = clusterFamily.getCursor ();
64       List JavaDoc targets = clusterFamily.getTargets ();
65
66       if (targets.size () == 0)
67          return null;
68       
69       if (cursor == FamilyClusterInfo.UNINITIALIZED_CURSOR)
70       {
71          // Obtain a random index into targets
72 cursor = RandomRobin.localRandomizer.nextInt(targets.size());
73       }
74       else
75       {
76          // Choose the next target
77 cursor = ( (cursor + 1) % targets.size() );
78       }
79       clusterFamily.setCursor (cursor);
80
81       return targets.get(cursor);
82    }
83
84 }
85
Popular Tags