package org.jgroups.protocols;
import org.jgroups.*;
import org.jgroups.annotations.Experimental;
import org.jgroups.annotations.GuardedBy;
import org.jgroups.annotations.Property;
import org.jgroups.annotations.Unsupported;
import org.jgroups.conf.PropertyConverters;
import org.jgroups.stack.AckMcastSenderWindow;
import org.jgroups.stack.AckReceiverWindow;
import org.jgroups.stack.Protocol;
import org.jgroups.stack.StaticInterval;
import org.jgroups.util.Util;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import java.util.Vector;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* Simple Multicast ACK protocol. A positive acknowledgment-based protocol for reliable delivery of
* multicast messages, which does not need any group membership service.
* Basically works as follows:
* <ul>
* <li>Sender S sends multicast message M</li>
* <li>When member P receives M, it sends back a unicast ack to S</li>
* <li>When S receives the ack from P, it checks whether P is in its
* membership list. If not, P will be added. This is necessary to retransmit the next message
* sent to P.</li>
* <li>When S sends a multicast message M, all members are added to a
* retransmission entry (containing all members to which the message
* was sent), which is added to a hashmap (keyed by seqno). Whenever
* an ack is received from receiver X, X will be removed from the
* retransmission list for the given seqno. When the retransmission
* list is empty, the seqno will be removed from the hashmap.</li>
* <li>A retransmitter thread in the sender periodically retransmits
* (either via unicast, or multicast) messages for which no ack has
* been received yet</li>
* <li>When a max number of (unsuccessful) retransmissions have been
* exceeded, all remaining members for that seqno are removed from
* the local membership, and the seqno is removed from the hashmap,
* ceasing all retransmissions</li>
* </ul>
* Advantage of this protocol: no group membership necessary, fast.
* @author Bela Ban Aug 2002
* <BR> Fix membershop bug: start a, b, kill b, restart b: b will be suspected by a.
*/
@Experimental @Unsupported
public class SMACK extends Protocol implements AckMcastSenderWindow.RetransmitCommand {
@Property(converter=PropertyConverters.LongArray.class)
long[] timeout=new long[]{1000,2000,3000}; // retransmit timeouts (for AckMcastSenderWindow)
@Property
int max_xmits=10; // max retransmissions (if still no ack, member will be removed)
final Set<Address> members=new LinkedHashSet<Address>(); // contains Addresses
AckMcastSenderWindow sender_win=null;
final Map<Address, AckReceiverWindow> receivers=Util.createConcurrentMap(); // keys=sender (Address), values=AckReceiverWindow
final Map<Address, Integer> xmit_table=Util.createConcurrentMap(); // keeps track of num xmits / member (keys: mbr, val:num)
Address local_addr=null; // my own address
@GuardedBy("lock")
long seqno=1; // seqno for msgs sent by this sender
final Lock lock=new ReentrantLock(); // for access to seqno
long vid=1; // for the fake view changes
@Property
boolean print_local_addr=true;
public SMACK() {
}
public void stop() {
if(sender_win != null) {
sender_win.stop();
sender_win=null;
}
for(AckReceiverWindow win: receivers.values()) {
win.reset();
}
receivers.clear();
}
public Object up(Event evt) {
Address sender;
switch(evt.getType()) {
case Event.SUSPECT:
if(log.isInfoEnabled()) log.info("removing suspected member " + evt.getArg());
removeMember((Address)evt.getArg());
break;
case Event.MSG:
Message msg=(Message)evt.getArg(), tmp_msg;
if(msg == null || msg.isFlagSet(Message.NO_RELIABILITY)) break;
sender=msg.getSrc();
SmackHeader hdr=(SmackHeader)msg.getHeader(this.id);
if(hdr == null) // is probably a unicast message
break;
switch(hdr.type) {
case SmackHeader.MCAST: // send an ack, then pass up (if not already received)
if(log.isTraceEnabled())
log.trace("received #" + hdr.seqno + " from " + sender);
AckReceiverWindow win=receivers.get(sender);
if(win == null) {
addMember(sender);
win=new AckReceiverWindow(hdr.seqno);
receivers.put(sender, win);
}
boolean added=win.add(hdr.seqno, msg);
Message ack_msg=new Message(sender);
ack_msg.putHeader(this.id, new SmackHeader(SmackHeader.ACK, hdr.seqno));
down_prot.down(new Event(Event.MSG, ack_msg));
// message is passed up if OOB. Later, when remove() is called, we discard it. This affects ordering !
// http://jira.jboss.com/jira/browse/JGRP-379
if(msg.isFlagSet(Message.OOB) && added) {
up_prot.up(new Event(Event.MSG, msg));
}
// now remove as many messages as possible
while((tmp_msg=win.remove()) != null) {
// discard OOB msg as it has already been delivered (http://jira.jboss.com/jira/browse/JGRP-379)
if(tmp_msg.isFlagSet(Message.OOB)) {
continue;
}
up_prot.up(new Event(Event.MSG, tmp_msg));
}
return null;
case SmackHeader.ACK:
addMember(msg.getSrc());
sender_win.ack(hdr.seqno, msg.getSrc());
sender_win.clearStableMessages();
if(log.isTraceEnabled())
log.trace("received ack for #" + hdr.seqno + " from " + msg.getSrc());
return null;
case SmackHeader.JOIN_ANNOUNCEMENT:
if(log.isInfoEnabled()) log.info("received join announcement by " + msg.getSrc());
if(!containsMember(sender)) {
Message join_rsp=new Message(sender);
join_rsp.putHeader(this.id, new SmackHeader(SmackHeader.JOIN_ANNOUNCEMENT, -1));
down_prot.down(new Event(Event.MSG, join_rsp));
}
addMember(sender);
return null;
case SmackHeader.LEAVE_ANNOUNCEMENT:
if(log.isInfoEnabled()) log.info("received leave announcement by " + msg.getSrc());
removeMember(sender);
return null;
default:
if(log.isWarnEnabled()) log.warn("detected SmackHeader with invalid type: " + hdr);
break;
}
break;
}
return up_prot.up(evt);
}
public Object down(Event evt) {
Message leave_msg;
switch(evt.getType()) {
case Event.DISCONNECT:
leave_msg=new Message();
leave_msg.putHeader(this.id, new SmackHeader(SmackHeader.LEAVE_ANNOUNCEMENT, -1));
down_prot.down(new Event(Event.MSG, leave_msg));
Util.sleep(100);
sender_win.stop();
break;
case Event.CONNECT:
Object ret=down_prot.down(evt);
sender_win=new AckMcastSenderWindow(this, new StaticInterval(timeout));
// send join announcement
Message join_msg=new Message();
join_msg.putHeader(this.id, new SmackHeader(SmackHeader.JOIN_ANNOUNCEMENT, -1));
down_prot.down(new Event(Event.MSG, join_msg));
return ret;
// add a header with the current sequence number and increment seqno
case Event.MSG:
Message msg=(Message)evt.getArg();
if(msg == null || msg.isFlagSet(Message.NO_RELIABILITY)) break;
if(msg.getDest() == null || msg.getDest().isMulticastAddress()) {
lock.lock();
try {
long msg_id=seqno;
msg.putHeader(this.id, new SmackHeader(SmackHeader.MCAST, msg_id));
sender_win.add(msg_id, msg, new Vector<Address>(members));
if(log.isTraceEnabled()) log.trace("sending mcast #" + msg_id);
seqno++;
}
finally {
lock.unlock();
}
}
break;
case Event.SET_LOCAL_ADDRESS:
local_addr=(Address)evt.getArg();
addMember(local_addr);
if(print_local_addr) {
System.out.println("\n-------------------------------------------------------\n" +
"GMS: address is " + local_addr +
"\n-------------------------------------------------------");
}
break;
}
return down_prot.down(evt);
}
/* ----------------------- Interface AckMcastSenderWindow.RetransmitCommand -------------------- */
public void retransmit(long seqno, Message msg, Address dest) {
msg.setDest(dest);
if(log.isInfoEnabled()) log.info(seqno + ", msg=" + msg);
down_prot.down(new Event(Event.MSG, msg));
}
/* -------------------- End of Interface AckMcastSenderWindow.RetransmitCommand ---------------- */
public static class SmackHeader extends Header {
public static final byte MCAST=1;
public static final byte ACK=2;
public static final byte JOIN_ANNOUNCEMENT=3;
public static final byte LEAVE_ANNOUNCEMENT=4;
byte type=0;
long seqno=-1;
public SmackHeader() {
}
public SmackHeader(byte type, long seqno) {
this.type=type;
this.seqno=seqno;
}
public int size() {
return Global.LONG_SIZE + Global.BYTE_SIZE;
}
public void writeTo(DataOutputStream out) throws IOException {
out.writeByte(type);
out.writeLong(seqno);
}
public void readFrom(DataInputStream in) throws IOException, IllegalAccessException, InstantiationException {
type=in.readByte();
seqno=in.readLong();
}
public String toString() {
switch(type) {
case MCAST:
return "MCAST";
case ACK:
return "ACK";
case JOIN_ANNOUNCEMENT:
return "JOIN_ANNOUNCEMENT";
case LEAVE_ANNOUNCEMENT:
return "LEAVE_ANNOUNCEMENT";
default:
return "<unknown>";
}
}
}
/* ------------------------------------- Private methods --------------------------------------- */
void addMember(Address mbr) {
Vector<Address> tmp=null;
synchronized(members) {
if(members.add(mbr)) {
tmp=new Vector<Address>(members);
}
}
if(tmp != null) {
if(log.isTraceEnabled())
log.trace("added " + mbr + ", members=" + tmp);
View new_view=new View(new ViewId(local_addr, vid++), tmp);
up_prot.up(new Event(Event.VIEW_CHANGE, new_view));
down_prot.down(new Event(Event.VIEW_CHANGE, new_view));
}
}
void removeMember(Address mbr) {
Vector<Address> tmp=null;
synchronized(members) {
if(members.remove(mbr))
tmp=new Vector<Address>(members);
}
if(tmp != null) {
if(log.isTraceEnabled())
log.trace("removed " + mbr + ", members=" + tmp);
View new_view=new View(new ViewId(local_addr, vid++), tmp);
up_prot.up(new Event(Event.VIEW_CHANGE, new_view));
down_prot.down(new Event(Event.VIEW_CHANGE, new_view));
if(sender_win != null)
sender_win.remove(mbr); // causes retransmissions to mbr to stop
for(Map.Entry<Address,AckReceiverWindow> entry: receivers.entrySet()) {
Address member=entry.getKey();
if(!members.contains(member)) {
AckReceiverWindow win=entry.getValue();
win.reset();
}
}
receivers.keySet().retainAll(members);
}
}
boolean containsMember(Address mbr) {
synchronized(members) {
return members.contains(mbr);
}
}
/* --------------------------------- End of Private methods ------------------------------------ */
}