Source Code Cross Referenced for ClientGmsImpl.java in  » Net » JGroups-2.4.1-sp3 » org » jgroups » protocols » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Net » JGroups 2.4.1 sp3 » org.jgroups.protocols 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // $Id: ClientGmsImpl.java,v 1.12.6.1 2007/04/27 08:03:51 belaban Exp $
002:
003:        package org.jgroups.protocols;
004:
005:        import org.jgroups.Address;
006:        import org.jgroups.Event;
007:        import org.jgroups.View;
008:        import org.jgroups.ViewId;
009:        import org.jgroups.blocks.GroupRequest;
010:        import org.jgroups.blocks.MethodCall;
011:        import org.jgroups.util.Util;
012:
013:        import java.util.Enumeration;
014:        import java.util.Hashtable;
015:        import java.util.Vector;
016:
017:        /**
018:         * Client part of GMS. Whenever a new member wants to join a group, it starts in the CLIENT role.
019:         * No multicasts to the group will be received and processed until the member has been joined and
020:         * turned into a SERVER (either coordinator or participant, mostly just participant). This class
021:         * only implements <code>Join</code> (called by clients who want to join a certain group, and
022:         * <code>ViewChange</code> which is called by the coordinator that was contacted by this client, to
023:         * tell the client what its initial membership is.
024:         * 
025:         * @author Bela Ban
026:         * @version $Revision: 1.12.6.1 $
027:         */
028:        public class ClientGmsImpl extends GmsImpl {
029:            final Vector initial_mbrs = new Vector(7);
030:            final Object view_installation_mutex = new Object();
031:            boolean joined = false;
032:
033:            public ClientGmsImpl(GMS g) {
034:                gms = g;
035:            }
036:
037:            public void init() {
038:                initial_mbrs.removeAllElements();
039:                joined = false;
040:            }
041:
042:            /**
043:             * Will generate a CONNECT_OK event. Determines the coordinator and sends a unicast
044:             * join() message to it. If successful, we wait for a ViewChange (can time out).
045:             * If view change is received, impl is changed to an instance of ParticipantGmsImpl.
046:             * Otherwise, we continue trying to send join() messages to	the coordinator,
047:             * until we succeed (or there is no member in the group. In this case, we create
048:             * our own singleton group).
049:             * <p>When GMS.disable_initial_coord is set to true, then we won't become coordinator on receiving an initial
050:             * membership of 0, but instead will retry (forever) until we get an initial membership of > 0.
051:             * 
052:             * @param mbr Our own address (assigned through SET_LOCAL_ADDRESS)
053:             */
054:            public void join(Address mbr) {
055:                Address coord;
056:                Event view_evt;
057:
058:                while (!joined) {
059:                    findInitialMembers();
060:                    if (joined) {
061:                        if (log.isInfoEnabled())
062:                            log.info("joined successfully");
063:                        return;
064:                    }
065:                    if (initial_mbrs.size() == 0) {
066:                        if (gms.disable_initial_coord) {
067:                            if (log.isInfoEnabled())
068:                                log
069:                                        .info("received an initial membership of 0, but "
070:                                                + "cannot become coordinator (disable_initial_coord="
071:                                                + gms.disable_initial_coord
072:                                                + "), will retry fetching the initial membership");
073:                            continue;
074:                        }
075:                        joined = true;
076:                        gms.view_id = new ViewId(mbr); // create singleton view with mbr as only member
077:                        gms.mbrs.add(mbr);
078:                        view_evt = new Event(Event.VIEW_CHANGE, GMS.makeView(
079:                                gms.mbrs.getMembers(), gms.view_id));
080:                        gms.passDown(view_evt);
081:                        gms.passUp(view_evt);
082:                        gms.becomeCoordinator();
083:
084:                        gms.passUp(new Event(Event.BECOME_SERVER));
085:                        gms.passDown(new Event(Event.BECOME_SERVER));
086:                        if (log.isInfoEnabled())
087:                            log.info("created group (first member)");
088:                        break;
089:                    }
090:
091:                    coord = determineCoord(initial_mbrs);
092:                    if (coord == null) {
093:                        if (log.isWarnEnabled())
094:                            log
095:                                    .warn("could not determine coordinator from responses "
096:                                            + initial_mbrs);
097:                        continue;
098:                    }
099:
100:                    synchronized (view_installation_mutex) {
101:                        try {
102:                            if (log.isInfoEnabled())
103:                                log.info("sending handleJoin() to " + coord);
104:                            MethodCall call = new MethodCall("handleJoin",
105:                                    new Object[] { mbr },
106:                                    new Class[] { Address.class });
107:                            gms.callRemoteMethod(coord, call,
108:                                    GroupRequest.GET_NONE, 0);
109:                            view_installation_mutex.wait(gms.join_timeout); // wait for view -> handleView()
110:                        } catch (Exception e) {
111:                            if (log.isErrorEnabled())
112:                                log.error("exception is " + e);
113:                            continue;
114:                        }
115:                    } // end synchronized
116:
117:                    if (joined) {
118:                        if (log.isInfoEnabled())
119:                            log.info("joined successfully");
120:                        return; // --> SUCCESS
121:                    } else {
122:                        if (log.isInfoEnabled())
123:                            log.info("failed, retrying");
124:                        Util.sleep(gms.join_retry_timeout);
125:                    }
126:
127:                } // end while
128:            }
129:
130:            public void leave(Address mbr) {
131:                wrongMethod("leave");
132:            }
133:
134:            public void suspect(Address mbr) {
135:                // wrongMethod("suspect");
136:            }
137:
138:            public void merge(Vector other_coords) {
139:                wrongMethod("merge");
140:            }
141:
142:            public boolean handleJoin(Address mbr) {
143:                wrongMethod("handleJoin");
144:                return false;
145:            }
146:
147:            /**
148:             * Returns false. Clients don't handle leave() requests
149:             */
150:            public void handleLeave(Address mbr, boolean suspected) {
151:                wrongMethod("handleLeave");
152:            }
153:
154:            /**
155:             * Install the first view in which we are a member. This is essentially a confirmation
156:             * of our JOIN request (see join() above).
157:             */
158:            public void handleViewChange(ViewId new_view, Vector mems) {
159:                if (gms.local_addr != null && mems != null
160:                        && mems.contains(gms.local_addr)) {
161:                    synchronized (view_installation_mutex) { // wait until JOIN is sent (above)
162:                        joined = true;
163:                        view_installation_mutex.notifyAll();
164:                        gms.installView(new_view, mems);
165:                        gms.becomeParticipant();
166:                        gms.passUp(new Event(Event.BECOME_SERVER));
167:                        gms.passDown(new Event(Event.BECOME_SERVER));
168:                    }
169:                    synchronized (initial_mbrs) { // in case findInitialMembers() is still running:
170:                        initial_mbrs.notifyAll(); // this will unblock it
171:                    }
172:                } else if (log.isWarnEnabled())
173:                    log.warn("am not member of " + mems
174:                            + ", will not install view");
175:            }
176:
177:            /**
178:             * Returns immediately. Clients don't handle merge() requests
179:             */
180:            public View handleMerge(ViewId other_view, Vector other_members) {
181:                wrongMethod("handleMerge");
182:                return null;
183:            }
184:
185:            /**
186:             * Returns immediately. Clients don't handle suspect() requests
187:             */
188:            public void handleSuspect(Address mbr) {
189:                wrongMethod("handleSuspect");
190:            }
191:
192:            public boolean handleUpEvent(Event evt) {
193:                Vector tmp;
194:
195:                switch (evt.getType()) {
196:
197:                case Event.FIND_INITIAL_MBRS_OK:
198:                    tmp = (Vector) evt.getArg();
199:                    synchronized (initial_mbrs) {
200:                        if (tmp != null && tmp.size() > 0)
201:                            for (int i = 0; i < tmp.size(); i++)
202:                                initial_mbrs.addElement(tmp.elementAt(i));
203:                        initial_mbrs.notifyAll();
204:                    }
205:                    return false; // don't pass up the stack
206:                }
207:
208:                return true;
209:            }
210:
211:            /* --------------------------- Private Methods ------------------------------------ */
212:
213:            /**
214:             * Pings initial members. Removes self before returning vector of initial members.
215:             * Uses IP multicast or gossiping, depending on parameters.
216:             */
217:            void findInitialMembers() {
218:                PingRsp ping_rsp;
219:
220:                synchronized (initial_mbrs) {
221:                    initial_mbrs.removeAllElements();
222:                    gms.passDown(Event.FIND_INITIAL_MBRS_EVT);
223:                    if (initial_mbrs.size() == 0) {
224:                        try {
225:                            initial_mbrs.wait();
226:                        } catch (Exception e) {
227:                        }
228:                    }
229:
230:                    for (int i = 0; i < initial_mbrs.size(); i++) {
231:                        ping_rsp = (PingRsp) initial_mbrs.elementAt(i);
232:                        if (ping_rsp.own_addr != null && gms.local_addr != null
233:                                && ping_rsp.own_addr.equals(gms.local_addr)) {
234:                            initial_mbrs.removeElementAt(i);
235:                            break;
236:                        }
237:                    }
238:                }
239:            }
240:
241:            /**
242:             * The coordinator is determined by a majority vote. If there are an equal number of votes for
243:             * more than 1 candidate, we determine the winner randomly.
244:             */
245:            Address determineCoord(Vector mbrs) {
246:                PingRsp mbr;
247:                Hashtable votes;
248:                int count, most_votes;
249:                Address winner = null, tmp;
250:
251:                if (mbrs == null || mbrs.size() < 1)
252:                    return null;
253:
254:                votes = new Hashtable(5);
255:
256:                // count *all* the votes (unlike the 2000 election)
257:                for (int i = 0; i < mbrs.size(); i++) {
258:                    mbr = (PingRsp) mbrs.elementAt(i);
259:                    if (mbr.coord_addr != null) {
260:                        if (!votes.containsKey(mbr.coord_addr))
261:                            votes.put(mbr.coord_addr, new Integer(1));
262:                        else {
263:                            count = ((Integer) votes.get(mbr.coord_addr))
264:                                    .intValue();
265:                            votes.put(mbr.coord_addr, new Integer(count + 1));
266:                        }
267:                    }
268:                }
269:
270:                if (votes.size() > 1)
271:                    if (log.isWarnEnabled())
272:                        log
273:                                .warn("there was more than 1 candidate for coordinator: "
274:                                        + votes);
275:                    else if (log.isInfoEnabled())
276:                        log.info("election results: " + votes);
277:
278:                // determine who got the most votes
279:                most_votes = 0;
280:                for (Enumeration e = votes.keys(); e.hasMoreElements();) {
281:                    tmp = (Address) e.nextElement();
282:                    count = ((Integer) votes.get(tmp)).intValue();
283:                    if (count > most_votes) {
284:                        winner = tmp;
285:                        // fixed July 15 2003 (patch submitted by Darren Hobbs, patch-id=771418)
286:                        most_votes = count;
287:                    }
288:                }
289:                votes.clear();
290:                return winner;
291:            }
292:
293:        }
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