package org.jgroups.protocols.pbcast;
import org.jgroups.*;
import org.jgroups.protocols.PingData;
import org.jgroups.util.Digest;
import org.jgroups.util.Promise;
import org.jgroups.util.Util;
import java.util.*;
/**
* Client part of GMS. Whenever a new member wants to join a group, it starts in the CLIENT role.
* No multicasts to the group will be received and processed until the member has been joined and
* turned into a SERVER (either coordinator or participant, mostly just participant). This class
* only implements <code>Join</code> (called by clients who want to join a certain group, and
* <code>ViewChange</code> which is called by the coordinator that was contacted by this client, to
* tell the client what its initial membership is.
* @author Bela Ban
* @version $Revision: 1.78 $
*/
public class ClientGmsImpl extends GmsImpl {
private final Promise<JoinRsp> join_promise=new Promise<JoinRsp>();
public ClientGmsImpl(GMS g) {
super(g);
}
public void init() throws Exception {
super.init();
join_promise.reset();
}
public void join(Address address,boolean useFlushIfPresent) {
joinInternal(address, false,useFlushIfPresent);
}
public void joinWithStateTransfer(Address local_addr, boolean useFlushIfPresent) {
joinInternal(local_addr,true,useFlushIfPresent);
}
/**
* Joins this process to a group. Determines the coordinator and sends a
* unicast handleJoin() message to it. The coordinator returns a JoinRsp and
* then broadcasts the new view, which contains a message digest and the
* current membership (including the joiner). The joiner is then supposed to
* install the new view and the digest and starts accepting mcast messages.
* Previous mcast messages were discarded (this is done in PBCAST).
* <p>
* If successful, impl is changed to an instance of ParticipantGmsImpl.
* Otherwise, we continue trying to send join() messages to the coordinator,
* until we succeed (or there is no member in the group. In this case, we
* create our own singleton group).
* <p>
* When GMS.disable_initial_coord is set to true, then we won't become
* coordinator on receiving an initial membership of 0, but instead will
* retry (forever) until we get an initial membership of > 0.
*
* @param mbr Our own address (assigned through SET_LOCAL_ADDRESS)
*/
private void joinInternal(Address mbr, boolean joinWithStateTransfer,boolean useFlushIfPresent) {
Address coord=null;
JoinRsp rsp=null;
View tmp_view;
long join_attempts=0;
leaving=false;
join_promise.reset();
while(!leaving) {
if(rsp == null && !join_promise.hasResult()) { // null responses means that the discovery was cancelled
List<PingData> responses=findInitialMembers(join_promise);
if (responses == null) {
// gray: we've seen this NPE here. not sure of the cases but wanted to add more debugging info
throw new NullPointerException("responses returned by findInitialMembers for " + join_promise + " is null");
}
// Sept 2008 (bela): break if we got a belated JoinRsp (https://jira.jboss.org/jira/browse/JGRP-687)
// Reverted above change again - bela June 2012, see https://github.com/belaban/JGroups/pull/29
if(join_promise.hasResult()) {
rsp=join_promise.getResult(gms.join_timeout); // clears the result
if(rsp != null)
continue;
}
if(responses.isEmpty()) {
if(log.isTraceEnabled())
log.trace(gms.local_addr + ": no initial members discovered: creating group as first member");
becomeSingletonMember(mbr);
return;
}
if(log.isTraceEnabled())
log.trace(gms.local_addr + ": initial_mbrs are " + print(responses));
coord=determineCoord(responses);
if(coord == null) { // e.g. because we have all clients only
if(gms.handle_concurrent_startup == false) {
if(log.isTraceEnabled())
log.trace("handle_concurrent_startup is false; ignoring responses of initial clients");
becomeSingletonMember(mbr);
return;
}
if(log.isTraceEnabled())
log.trace("could not determine coordinator from responses " + responses);
// so the member to become singleton member (and thus coord) is the first of all clients
SortedSet<Address> clients=new TreeSet<Address>(); // sorted
clients.add(mbr); // add myself again (was removed by findInitialMembers())
for(PingData response: responses) {
Address client_addr=response.getAddress();
if(client_addr != null)
clients.add(client_addr);
}
if(log.isTraceEnabled())
log.trace("clients to choose new coord from are: " + clients);
Address new_coord=clients.first();
if(new_coord.equals(mbr)) {
if(log.isTraceEnabled())
log.trace("I (" + mbr + ") am the first of the clients, will become coordinator");
becomeSingletonMember(mbr);
return;
}
else {
if(log.isTraceEnabled())
log.trace("I (" + mbr
+ ") am not the first of the clients, waiting for another client to become coordinator");
Util.sleep(500);
}
continue;
}
if(log.isDebugEnabled())
log.debug("sending JOIN(" + mbr + ") to " + coord);
sendJoinMessage(coord,mbr,joinWithStateTransfer,useFlushIfPresent);
}
if(rsp == null)
rsp=join_promise.getResult(gms.join_timeout);
if(rsp == null) {
join_attempts++;
if(log.isWarnEnabled())
log.warn("JOIN(" + mbr + ") sent to " + coord + " timed out (after " + gms.join_timeout + " ms), on try " + join_attempts);
if(gms.max_join_attempts != 0 && join_attempts >= gms.max_join_attempts) {
if(log.isWarnEnabled())
log.warn("Too many JOIN attempts: becoming singleton");
becomeSingletonMember(mbr);
return;
}
continue;
}
// 1. check whether JOIN was rejected
String failure=rsp.getFailReason();
if(failure != null)
throw new SecurityException(failure);
// 2. Install digest
if(rsp.getDigest() == null || rsp.getDigest().size() == 0) {
if(log.isWarnEnabled())
log.warn("digest response has no senders: digest=" + rsp.getDigest());
rsp=null;
continue;
}
final Digest tmp_digest=rsp.getDigest();
tmp_view=rsp.getView();
if(tmp_view == null) {
if(log.isErrorEnabled())
log.error("JoinRsp has a null view, skipping it");
rsp=null;
}
else {
if(!tmp_digest.contains(gms.local_addr)) {
throw new IllegalStateException("digest returned from " + coord + " with JOIN_RSP does not contain myself (" +
gms.local_addr + "): join response: " + rsp);
}
if(log.isTraceEnabled())
log.trace(gms.local_addr + ": JOIN-RSP=" + tmp_view + " [size=" + tmp_view.size() + "]\n\n");
if(!installView(tmp_view, tmp_digest)) {
if(log.isErrorEnabled())
log.error("view installation failed, retrying to join group");
rsp=null;
continue;
}
// send VIEW_ACK to sender of view
Message view_ack=new Message(coord, null, null);
view_ack.setFlag(Message.OOB);
GMS.GmsHeader tmphdr=new GMS.GmsHeader(GMS.GmsHeader.VIEW_ACK);
view_ack.putHeader(gms.getId(), tmphdr);
gms.getDownProtocol().down(new Event(Event.MSG, view_ack));
return;
}
}
}
@SuppressWarnings("unchecked")
private List<PingData> findInitialMembers(Promise<JoinRsp> promise) {
List<PingData> responses=(List<PingData>)gms.getDownProtocol().down(new Event(Event.FIND_INITIAL_MBRS, promise));
if(responses != null) {
for(Iterator<PingData> iter=responses.iterator(); iter.hasNext();) {
Address address=iter.next().getAddress();
if(address != null && address.equals(gms.local_addr))
iter.remove();
}
}
return responses;
}
public void leave(Address mbr) {
leaving=true;
wrongMethod("leave");
}
public void handleJoinResponse(JoinRsp join_rsp) {
join_promise.setResult(join_rsp); // will wake up join() method
}
/* --------------------------- Private Methods ------------------------------------ */
/**
* Called by join(). Installs the view returned by calling Coord.handleJoin() and becomes coordinator.
*/
private boolean installView(View new_view, Digest digest) {
List<Address> mems=new_view.getMembers();
if(gms.local_addr == null || mems == null || !mems.contains(gms.local_addr)) {
if(log.isErrorEnabled())
log.error("I (" + gms.local_addr + ") am not member of " + mems + ", will not install view");
return false;
}
gms.installView(new_view, digest);
gms.becomeParticipant();
gms.getUpProtocol().up(new Event(Event.BECOME_SERVER));
gms.getDownProtocol().down(new Event(Event.BECOME_SERVER));
return true;
}
protected static String print(List<PingData> rsps) {
StringBuilder sb=new StringBuilder();
for(PingData rsp: rsps)
sb.append(rsp.getAddress() + " ");
return sb.toString();
}
void sendJoinMessage(Address coord, Address mbr,boolean joinWithTransfer, boolean useFlushIfPresent) {
Message msg;
GMS.GmsHeader hdr;
msg=new Message(coord, null, null);
msg.setFlag(Message.OOB);
if(joinWithTransfer)
hdr=new GMS.GmsHeader(GMS.GmsHeader.JOIN_REQ_WITH_STATE_TRANSFER, mbr,useFlushIfPresent);
else
hdr=new GMS.GmsHeader(GMS.GmsHeader.JOIN_REQ, mbr,useFlushIfPresent);
msg.putHeader(gms.getId(), hdr);
gms.getDownProtocol().down(new Event(Event.MSG, msg));
}
/**
The coordinator is determined by a majority vote. If there are an equal number of votes for
more than 1 candidate, we determine the winner randomly.
*/
private Address determineCoord(List<PingData> mbrs) {
int count, most_votes;
Address winner=null, tmp;
if(mbrs == null || mbrs.size() < 1)
return null;
Map<Address,Integer> votes=new HashMap<Address,Integer>(5);
// count *all* the votes (unlike the 2000 election)
for(PingData mbr: mbrs) {
if(mbr.hasCoord()) {
if(!votes.containsKey(mbr.getCoordAddress()))
votes.put(mbr.getCoordAddress(), 1);
else {
count=votes.get(mbr.getCoordAddress());
votes.put(mbr.getCoordAddress(), count + 1);
}
}
}
// we have seen members say someone else is coordinator but they disagree
for(PingData mbr: mbrs) {
// remove members who don't agree with the election (Florida)
if (votes.containsKey(mbr.getAddress()) && (!mbr.isCoord())) {
votes.remove(mbr.getAddress());
}
}
if(votes.size() > 1) {
if(log.isWarnEnabled()) log.warn("there was more than 1 candidate for coordinator: " + votes);
}
else {
if(log.isDebugEnabled()) log.debug("election results: " + votes);
}
// determine who got the most votes
most_votes=0;
for(Map.Entry<Address,Integer> entry: votes.entrySet()) {
tmp=entry.getKey();
count=entry.getValue();
if(count > most_votes) {
winner=tmp;
// fixed July 15 2003 (patch submitted by Darren Hobbs, patch-id=771418)
most_votes=count;
}
}
votes.clear();
return winner;
}
void becomeSingletonMember(Address mbr) {
Digest initial_digest;
ViewId view_id;
List<Address> mbrs=new ArrayList<Address>(1);
// set the initial digest (since I'm the first member)
initial_digest=new Digest(gms.local_addr, 0, 0); // initial seqno mcast by me will be 1 (highest seen +1)
gms.setDigest(initial_digest);
view_id=new ViewId(mbr); // create singleton view with mbr as only member
mbrs.add(mbr);
View new_view=new View(view_id, mbrs);
gms.installView(new_view);
gms.becomeCoordinator(); // not really necessary - installView() should do it
gms.getUpProtocol().up(new Event(Event.BECOME_SERVER));
gms.getDownProtocol().down(new Event(Event.BECOME_SERVER));
if(log.isDebugEnabled()) log.debug("created group (first member). My view is " + gms.getViewId() +
", impl is " + gms.getImpl().getClass().getName());
}
}