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package protocols.implementations;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Vector;
import core.VSMessage;
import protocols.VSAbstractProtocol;
/**
* The class VSBerkelyTimeProtocol, an implementation of the berkely time
* protocol.
*
* @author Paul C. Buetow
*/
public class VSBerkelyTimeProtocol extends VSAbstractProtocol {
/**
* Instantiates a new berkely time protocol.
*/
public VSBerkelyTimeProtocol() {
super(VSAbstractProtocol.HAS_ON_SERVER_START);
setClassname(getClass().toString());
}
/** Integer: Process ID, Long: Local time of the process */
private HashMap<Integer,Long> processTimes = new HashMap<Integer,Long>();
/** Integer: Process ID, Long: Time of receiving the response from the
* process
*/
private HashMap<Integer,Long> recvTimes = new HashMap<Integer,Long>();
/** Integer: Process ID, Long: Calculated process times (using the RTT) */
private HashMap<Integer,Long> realTimesRTT = new HashMap<Integer,Long>();
/** Contains all process IDs of processes which want to justify their
* time
*/
private ArrayList<Integer> peers = new ArrayList<Integer>();
/** Time the request/response has started */
private long requestTime;
/* (non-Javadoc)
* @see events.VSAbstractProtocol#onServerInit()
*/
public void onServerInit() {
Vector<Integer> vec = new Vector<Integer>();
vec.add(1);
vec.add(3);
initVector("pids", vec, "PIDs of participating processes");
}
/* (non-Javadoc)
* @see protocols.VSAbstractProtocol#onServerReset()
*/
public void onServerReset() {
//System.out.println("FOOBAR");
processTimes.clear();
recvTimes.clear();
realTimesRTT.clear();
peers.clear();
}
/* (non-Javadoc)
* @see protocols.VSAbstractProtocol#onServerStart()
*/
public void onServerStart() {
//System.out.println("FOO");
peers.addAll(getVector("pids"));
requestTime = process.getTime();
VSMessage message = new VSMessage();
message.setBoolean("isRequest", true);
sendMessage(message);
}
/* (non-Javadoc)
* @see protocols.VSAbstractProtocol#onServerRecv(core.VSMessage)
*/
public void onServerRecv(VSMessage recvMessage) {
/* Ignore all protocol messages which are not a response message,
e.g. itself */
if (!recvMessage.getBoolean("isResponse"))
return;
Integer processID = recvMessage.getIntegerObj("processID");
if (peers.contains(processID))
peers.remove(processID);
else
return; /* Process has been handled already or is not listed */
Long time = Long.valueOf(recvMessage.getLong("time"));
processTimes.put(processID, time);
recvTimes.put(processID, Long.valueOf(process.getTime()));
/* All peers have told their times */
if (peers.size() == 0) {
long avgTime = calculateAverageTime();
/* Set the local's process time to the new avg reference time */
process.setTime(avgTime);
/* Tell all other processes what to do in order to justify their
times */
sendJustifyRequests(avgTime);
/* Start "clean" next time */
onServerReset();
}
}
/* (non-Javadoc)
* @see protocols.VSAbstractProtocol#onServerSchedule()
*/
public void onServerSchedule() {
}
/**
* Calculate the new average time.
*
* @return the long
*/
private long calculateAverageTime() {
long sum = 0;
for (Integer processID : processTimes.keySet()) {
Long localTime = processTimes.get(processID);
Long recvTime = recvTimes.get(processID);
long rtt = recvTime.longValue() - requestTime;
long realProcessTime = localTime + (long) (rtt / 2);
realTimesRTT.put(processID, Long.valueOf(realProcessTime));
sum += realProcessTime;
}
/* Include the time of the local process */
sum += process.getTime();
return (long) sum / (getVector("pids").size() + 1);
}
/**
* Sends to all clients a value to justify their local clocks.
*
* @param avgTime the avg time
*/
private void sendJustifyRequests(long avgTime) {
for (Integer processID : processTimes.keySet()) {
long realProcessTime = realTimesRTT.get(processID).longValue();
long diff = avgTime - realProcessTime;
VSMessage message = new VSMessage();
message.setBoolean("isJustify", true);
message.setLong("timeDiff", diff);
message.setInteger("receiverProcessID", processID);
sendMessage(message);
}
}
/* (non-Javadoc)
* @see events.VSAbstractProtocol#onClientInit()
*/
public void onClientInit() {
}
/* (non-Javadoc)
* @see protocols.VSAbstractProtocol#onClientReset()
*/
public void onClientReset() {
}
/* (non-Javadoc)
* @see protocols.VSAbstractProtocol#onClientRecv(core.VSMessage)
*/
public void onClientRecv(VSMessage recvMessage) {
if (recvMessage.getBoolean("isRequest")) {
VSMessage message = new VSMessage();
message.setInteger("processID", process.getProcessID());
message.setLong("time", process.getTime());
message.setBoolean("isResponse", true);
sendMessage(message);
} else if (recvMessage.getBoolean("isJustify")) {
/* Check if it's "my" justify message */
if (recvMessage.getInteger("receiverProcessID") !=
process.getProcessID())
return;
long timeDiff = recvMessage.getLong("timeDiff");
//long recvTime = process.getTime();
long newTime = process.getTime() + timeDiff;
log("New time: " + newTime);
process.setTime(newTime);
}
}
/* (non-Javadoc)
* @see protocols.VSAbstractProtocol#onClientSchedule()
*/
public void onClientSchedule() {
}
/* (non-Javadoc)
* @see protocols.VSAbstractProtocol#toString()
*/
public String toString() {
return super.toString();
}
}
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