// $Id: FD.java,v 1.9 2005/08/11 12:43:46 belaban Exp $
package org.jgroups.protocols.pbcast;
import org.jgroups.Address;
import org.jgroups.Event;
import org.jgroups.Message;
import org.jgroups.View;
import org.jgroups.stack.Protocol;
import org.jgroups.util.Util;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Properties;
import java.util.Vector;
/**
* Passive failure detection protocol. It assumes a pbcast protocol, which uses rounds of gossiping for
* reliable message delivery. Gossip protocols typically involve all the members sending gossips in regular
* intervals. This protocol therefore works as follows: it allocates a timestamp for each member and updates
* the timestamp whenever it receives a message from a sender P. Any type of message is accepted from P. For
* example, PBCAST regularly sends the following messages:
* <ul>
* <li>regular mcast message from P
* <li>regular ucast message from P
* <li>gossip from P
* <li>retransmit request from P
* <li>retransmit response from P
* </ul>
*
* @author Bela Ban
*/
public class FD extends Protocol implements Runnable {
Address local_addr=null;
Thread checker=null; // checks timestamps for timeout, generates SUSPECT event
final Object checker_lock=new Object();
long timeout=6000; // number of millisecs to wait for a member to be suspected
// (should be higher than the gossip_interval value in PBCAST
final Hashtable members=new Hashtable(11); // keys=Addresses (members), vals=Entries (timestamp)
final Vector suspected_mbrs=new Vector(11); // currently suspected members (dynamically updated)
static class Entry {
long timestamp;
Entry(long timestamp) {
this.timestamp=timestamp;
}
public String toString() {
return Long.toString(timestamp);
}
}
public String getName() {
return "FD";
}
public boolean setProperties(Properties props) {
String str;
super.setProperties(props);
str=props.getProperty("timeout");
if(str != null) {
timeout=Long.parseLong(str);
props.remove("timeout");
}
if(props.size() > 0) {
log.error("FD.setProperties(): the following properties are not recognized: " + props);
return false;
}
return true;
}
public void stop() {
stopChecker();
}
public void up(Event evt) {
Message msg;
Address sender;
switch(evt.getType()) {
case Event.SET_LOCAL_ADDRESS:
local_addr=(Address)evt.getArg();
break;
case Event.MSG:
msg=(Message)evt.getArg();
sender=msg.getSrc();
updateSender(sender);
break;
}
passUp(evt); // pass up to the layer above us
}
public void down(Event evt) {
View v;
Vector mbrs;
Address mbr;
switch(evt.getType()) {
case Event.VIEW_CHANGE:
v=(View)evt.getArg();
mbrs=v.getMembers();
passDown(evt);
for(Enumeration e=members.keys(); e.hasMoreElements();) {
mbr=(Address)e.nextElement();
if(!mbrs.contains(mbr)) {
members.remove(mbr);
}
}
members.remove(local_addr);
if(members.size() > 0 && checker == null)
startChecker();
return;
// generated by PBCAST, contains list of members a gossip has visited. we can safely reset their counter
case Event.HEARD_FROM:
updateSenders((Vector)evt.getArg());
return; // don't pass down
}
passDown(evt);
}
public void run() {
Address mbr;
long timestamp, diff;
while(checker != null && Thread.currentThread().equals(checker) && members.size() > 0) {
for(Enumeration e=members.keys(); e.hasMoreElements();) {
mbr=(Address)e.nextElement();
timestamp=((Entry)members.get(mbr)).timestamp;
diff=System.currentTimeMillis() - timestamp;
if(diff >= timeout) {
if(log.isInfoEnabled()) log.info("suspecting " + mbr);
passUp(new Event(Event.SUSPECT, mbr));
if(!suspected_mbrs.contains(mbr))
suspected_mbrs.addElement(mbr);
}
}
Util.sleep(timeout);
}
checker=null;
}
void startChecker() {
synchronized(checker_lock) {
if(checker == null) {
checker=new Thread(this, "FD.CheckerThread");
checker.setDaemon(true);
checker.start();
}
}
}
void stopChecker() {
Thread tmp;
synchronized(checker_lock) {
if(checker != null && checker.isAlive()) {
tmp=checker;
checker=null;
tmp.interrupt();
try {
tmp.join(timeout);
}
catch(Exception ex) {
}
if(tmp.isAlive())
if(warn) log.warn("interrupted checker thread is still alive !");
}
checker=null;
}
}
void updateSender(Address mbr) {
Entry entry;
long curr_time;
if(mbr == null) {
if(log.isDebugEnabled()) log.debug("member " + mbr + " not found");
return;
}
if(suspected_mbrs.size() > 0 && suspected_mbrs.contains(mbr)) {
passUp(new Event(Event.UNSUSPECT, mbr));
suspected_mbrs.remove(mbr);
}
if(mbr.equals(local_addr))
return;
entry=(Entry)members.get(mbr);
curr_time=System.currentTimeMillis();
if(entry != null)
entry.timestamp=curr_time;
else
members.put(mbr, new Entry(curr_time));
}
void updateSenders(Vector v) {
Address mbr;
if(v == null) return;
for(int i=0; i < v.size(); i++) {
mbr=(Address)v.elementAt(i);
updateSender(mbr);
}
}
String printTimestamps() {
StringBuffer sb=new StringBuffer();
Address mbr;
synchronized(members) {
for(Enumeration e=members.keys(); e.hasMoreElements();) {
mbr=(Address)e.nextElement();
sb.append("\n" + mbr + ": " + (System.currentTimeMillis() - ((Entry)members.get(mbr)).timestamp));
}
}
return sb.toString();
}
}