LoadBalancingConf


1   /*
2     Copyright (C) 2001 Renaud Pawlak
3   
4     This program is free software; you can redistribute it and/or modify
5     it under the terms of the GNU Lesser General Public License as
6     published by the Free Software Foundation; either version 2 of the
7     License, or (at your option) any later version.
8   
9     This program is distributed in the hope that it will be useful,
10    but WITHOUT ANY WARRANTY; without even the implied warranty of
11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12    GNU Lesser General Public License for more details.
13  
14    You should have received a copy of the GNU Lesser General Public License
15    along with this program; if not, write to the Free Software
16    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
17  
18  package org.objectweb.jac.aspects.distribution;
19  
20  /**
21   * This is the configuration interface of the load-balancing aspect
22   *
23   * @see LoadBalancingAC
24   * @author Renaud Pawlak
25   */
26  
27  public interface LoadBalancingConf {
28  
29     /**
30      * This configuration method allows the user to define a round-trip
31      * load-balancer on a replication group.
32      *
33      * <p>It assumes that a replication group exists on a set of host
34      * denoted by <code>replicaExpr</code>. It also assumes that an
35      * uncorrelated replica called <code>wrappeeName</code> exists on
36      * <code>hostName</code>. Note that this distributed scheme can be
37      * easilly obtained by configuring the deployment aspect for an
38      * object <code>myObject</code> like this:
39      *
40      * <pre>
41      * replicated "myObject" ".*[1-6]"
42      * </pre>
43      *
44      * <p>This means that <code>myObject</code> is replicated on all
45      * the hosts one to six and that the replicas are strongly
46      * consistent. Then, you can configure the load-balancing:
47      *
48      * <pre>
49      * addRoundTripLoadBalancer "photorepository0" ".*" "s0" ".*[1-6]"
50      * </pre>
51      *
52      * <p>Note that the round-trip balancer (located on s0) changes the
53      * replica it uses for each invocation. The followed sequence is
54      * 1,2,3,4,5,6,1,2,3,4,5,6,1,...
55      *
56      * <p>An alternative to the round-trip load-balancer is the random
57      * load-balancer that randomly picks out the next replica to
58      * use. This can be useful when a total decoralation is needed for
59      * all clients.
60      *
61      * @param wrappeeName the name of the object that is replicated and
62      * that will act as a load-balancer proxy 
63      * @param methods a pointcut expression for the method that perform
64      * the load-balancing (others perform local calls)
65      * @param hostName the host where the proxy load-balances
66      * @param replicaExpr a regular expression that matches all the
67      * hosts of the topology where the replicas are located
68      *
69      * @see #addRandomLoadBalancer(String,String,String,String) */
70      
71  
72     void addRoundTripLoadBalancer( String   wrappeeName,
73                                    String   methods,
74                                    String   hostName, 
75                                    String   replicaExpr );
76     
77     /**
78      * This configuration method allows the user to define a random
79      * load-balancer on a replication group.
80      *
81      * <p>It follows the same principles as a round-trip balancer but
82      * picks up the next replica to use randomly.
83      * 
84      * @see #addRoundTripLoadBalancer(String,String,String,String) */
85  
86     void addRandomLoadBalancer( String   wrappeeName,
87                                 String   methods,
88                                 String   hostName, 
89                                 String   replicaExpr );
90  
91  }
92  
93  
94  
95  
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