VIEW_ENFORCER


1   // $Id: VIEW_ENFORCER.java,v 1.3 2004/04/23 19:36:13 belaban Exp $
2   
3   package org.jgroups.protocols;
4   
5   import org.jgroups.Address;
6   import org.jgroups.Event;
7   import org.jgroups.View;
8   import org.jgroups.stack.Protocol;
9   
10  import java.util.Vector  ;
11  
12  
13  /**
14   * Used by a client until it becomes a member: all up messages are discarded until a VIEW_CHANGE
15   * is encountered. From then on, this layer just acts as a pass-through layer. Later, we may
16   * add some functionality that checks for the VIDs of messages and discards messages accordingly.
17   */
18  
19  public class VIEW_ENFORCER extends Protocol {
20      Address local_addr=null;
21      boolean is_member=false;
22  
23  
24      /**
25       * All protocol names have to be unique !
26       */
27      public String   getName() {
28          return "VIEW_ENFORCER";
29      }
30  
31  
32      public void up(Event evt) {
33  
34          switch(evt.getType()) {
35  
36              case Event.VIEW_CHANGE:
37                  if(is_member)       // pass the view change up if we are already a member of the group
38                      break;
39  
40                  Vector   new_members=((View)evt.getArg()).getMembers();
41                  if(new_members == null || new_members.size() == 0)
42                      break;
43                  if(local_addr == null) {
44                      System.err.println("VIEW_ENFORCER.up(VIEW_CHANGE): local address is null; cannot check " +
45                              "whether I'm a member of the group; discarding view change");
46                      return;
47                  }
48  
49                  if(new_members.contains(local_addr))
50                      is_member=true;
51                  else
52                      return;
53  
54                  break;
55  
56              case Event.SET_LOCAL_ADDRESS:
57                  local_addr=(Address)evt.getArg();
58                  break;
59  
60  
61              case Event.MSG:
62                  if(!is_member) {    // drop message if we are not yet member of the group
63                      if(log.isInfoEnabled()) log.info("dropping message " + evt.getArg());
64                      return;
65                  }
66                  break;
67  
68          }
69          passUp(evt);            // Pass up to the layer above us
70      }
71  
72  
73  }
74
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