ParticipantGmsImpl


1   // $Id: ParticipantGmsImpl.java,v 1.9 2004/09/23 16:29:38 belaban Exp $
2   
3   package org.jgroups.protocols.pbcast;
4   
5   import org.jgroups.Address;
6   import org.jgroups.Event;
7   import org.jgroups.Message;
8   import org.jgroups.View;
9   import org.jgroups.util.Promise;
10  
11  import java.util.Vector  ;
12  
13  
14  public class ParticipantGmsImpl extends GmsImpl {
15      private final Vector       suspected_mbrs=new Vector  (11);
16      private final Promise    leave_promise=new Promise();
17  
18  
19      public ParticipantGmsImpl(GMS g) {
20          gms=g;
21      }
22  
23  
24      public void init() throws Exception   {
25          super.init();
26          suspected_mbrs.removeAllElements();
27          leave_promise.reset();
28      }
29  
30      public void join(Address mbr) {
31          wrongMethod("join");
32      }
33  
34  
35      /**
36       * Loop: determine coord. If coord is me --> handleLeave().
37       * Else send handleLeave() to coord until success
38       */
39      public void leave(Address mbr) {
40          Address coord;
41          int max_tries=3;
42          Object   result;
43  
44          leave_promise.reset();
45  
46          if(mbr.equals(gms.local_addr))
47              leaving=true;
48  
49          while((coord=gms.determineCoordinator()) != null && max_tries-- > 0) {
50              if(gms.local_addr.equals(coord)) {            // I'm the coordinator
51                  gms.becomeCoordinator();
52                  gms.getImpl().handleLeave(mbr, false);    // regular leave
53                  return;
54              }
55  
56              if(log.isDebugEnabled()) log.debug("sending LEAVE request to " + coord);
57              sendLeaveMessage(coord, mbr);
58              synchronized(leave_promise) {
59                  result=leave_promise.getResult(gms.leave_timeout);
60                  if(result != null)
61                      break;
62              }
63          }
64          gms.becomeClient();
65      }
66  
67  
68      public void handleJoinResponse(JoinRsp join_rsp) {
69          wrongMethod("handleJoinResponse");
70      }
71  
72      public void handleLeaveResponse() {
73          if(leave_promise == null) {
74              if(log.isErrorEnabled()) log.error("leave_promise is null");
75              return;
76          }
77          synchronized(leave_promise) {
78              leave_promise.setResult(Boolean.TRUE);  // unblocks thread waiting in leave()
79          }
80      }
81  
82  
83      public void suspect(Address mbr) {
84          handleSuspect(mbr);
85      }
86  
87  
88      /** Removes previously suspected member from list of currently suspected members */
89      public void unsuspect(Address mbr) {
90          if(mbr != null)
91              suspected_mbrs.remove(mbr);
92      }
93  
94  
95      public JoinRsp handleJoin(Address mbr) {
96          wrongMethod("handleJoin");
97          return null;
98      }
99  
100 
101     public void handleLeave(Address mbr, boolean suspected) {
102         wrongMethod("handleLeave");
103     }
104 
105 
106     /**
107      * If we are leaving, we have to wait for the view change (last msg in the current view) that
108      * excludes us before we can leave.
109      * @param new_view The view to be installed
110      * @param digest   If view is a MergeView, digest contains the seqno digest of all members and has to
111      *                 be set by GMS
112      */
113     public void handleViewChange(View new_view, Digest digest) {
114         Vector   mbrs=new_view.getMembers();
115          if(log.isDebugEnabled()) log.debug("view=" + new_view);
116         suspected_mbrs.removeAllElements();
117         if(leaving && !mbrs.contains(gms.local_addr)) { // received a view in which I'm not member: ignore
118             return;
119         }
120         gms.installView(new_view, digest);
121     }
122 
123 
124     public void handleSuspect(Address mbr) {
125         Vector   suspects=null;
126 
127         if(mbr == null) return;
128         if(!suspected_mbrs.contains(mbr))
129             suspected_mbrs.addElement(mbr);
130         
131         if(log.isDebugEnabled()) log.debug("suspected mbr=" + mbr + ", suspected_mbrs=" + suspected_mbrs);
132 
133         if(wouldIBeCoordinator()) {
134             if(log.isDebugEnabled()) log.debug("suspected mbr=" + mbr + "), members are " +
135                     gms.members + ", coord=" + gms.local_addr + ": I'm the new coord !");
136 
137             suspects=(Vector  )suspected_mbrs.clone();
138             suspected_mbrs.removeAllElements();
139             gms.becomeCoordinator();
140             gms.castViewChange(null, null, suspects);
141         }
142     }
143 
144 
145     /* ---------------------------------- Private Methods --------------------------------------- */
146 
147     /**
148      * Determines whether this member is the new coordinator given a list of suspected members.  This is
149      * computed as follows: the list of currently suspected members (suspected_mbrs) is removed from the current
150      * membership. If the first member of the resulting list is equals to the local_addr, then it is true,
151      * otherwise false. Example: own address is B, current membership is {A, B, C, D}, suspected members are {A,
152      * D}. The resulting list is {B, C}. The first member of {B, C} is B, which is equal to the
153      * local_addr. Therefore, true is returned.
154      */
155     boolean wouldIBeCoordinator() {
156         Address new_coord=null;
157         Vector   mbrs=gms.members.getMembers(); // getMembers() returns a *copy* of the membership vector
158 
159         for(int i=0; i < suspected_mbrs.size(); i++)
160             mbrs.removeElement(suspected_mbrs.elementAt(i));
161 
162         if(mbrs.size() < 1) return false;
163         new_coord=(Address)mbrs.elementAt(0);
164         return gms.local_addr.equals(new_coord);
165     }
166 
167 
168     void sendLeaveMessage(Address coord, Address mbr) {
169         Message msg=new Message(coord, null, null);
170         GMS.GmsHeader hdr=new GMS.GmsHeader(GMS.GmsHeader.LEAVE_REQ, mbr);
171 
172         msg.putHeader(gms.getName(), hdr);
173         gms.passDown(new Event(Event.MSG, msg));
174     }
175 
176 
177     /* ------------------------------ End of Private Methods ------------------------------------ */
178 
179 }
180
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags