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* Clock:

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- getFramedAveragePeerClockSkew() now returns a long (ms);
        was a Long (s)
      - Implement NTP-style clock slewing so the clock is adjusted
        gradually
      - Implement clock strata so we prefer better clocks
      - Implement a timestamper in the transport so we will periodically
        update the clock even if NTP is not working
        This allows the router to converge the clock instead of simply
        hoping the first connected peer is correct.
      - Slow down NTP attempts after several consecutive failures
This commit is contained in:
zzz
2010-02-13 01:20:23 +00:00
parent 375118fe02
commit 4f70a7d0fe
7 changed files with 240 additions and 45 deletions
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44
core/java/src/net/i2p/time/NtpClient.java
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@ -76,12 +76,46 @@ public class NtpClient {
throw new IllegalArgumentException("No reachable NTP servers specified");
}
/**
* Query the ntp servers, returning the current time from first one we find
* Hack to return time and stratum
* @return time in rv[0] and stratum in rv[1]
* @throws IllegalArgumentException if none of the servers are reachable
* @since 0.7.12
*/
public static long[] currentTimeAndStratum(String serverNames[]) {
if (serverNames == null)
throw new IllegalArgumentException("No NTP servers specified");
ArrayList names = new ArrayList(serverNames.length);
for (int i = 0; i < serverNames.length; i++)
names.add(serverNames[i]);
Collections.shuffle(names);
for (int i = 0; i < names.size(); i++) {
long[] rv = currentTimeAndStratum((String)names.get(i));
if (rv != null && rv[0] > 0)
return rv;
}
throw new IllegalArgumentException("No reachable NTP servers specified");
}
/**
* Query the given NTP server, returning the current internet time
*
* @return milliseconds since january 1, 1970 (UTC), or -1 on error
*/
public static long currentTime(String serverName) {
long[] la = currentTimeAndStratum(serverName);
if (la != null)
return la[0];
return -1;
}
/**
* Hack to return time and stratum
* @return time in rv[0] and stratum in rv[1], or null for error
* @since 0.7.12
*/
private static long[] currentTimeAndStratum(String serverName) {
try {
// Send request
DatagramSocket socket = new DatagramSocket();
@ -104,7 +138,7 @@ public class NtpClient {
socket.receive(packet);
} catch (InterruptedIOException iie) {
socket.close();
return -1;
return null;
}
// Immediately record the incoming timestamp
@ -123,15 +157,17 @@ public class NtpClient {
// Anything else is right out, treat such responses like errors
if ((msg.stratum < 1) || (msg.stratum > 15)) {
//System.out.println("Response from NTP server of unacceptable stratum " + msg.stratum + ", failing.");
return(-1);
return null;
}
long rv = (long)(System.currentTimeMillis() + localClockOffset*1000);
long[] rv = new long[2];
rv[0] = (long)(System.currentTimeMillis() + localClockOffset*1000);
rv[1] = msg.stratum;
//System.out.println("host: " + address.getHostAddress() + " rtt: " + roundTripDelay + " offset: " + localClockOffset + " seconds");
return rv;
} catch (IOException ioe) {
//ioe.printStackTrace();
return -1;
return null;
}
}

32
core/java/src/net/i2p/time/Timestamper.java
View File

@ -23,6 +23,7 @@ public class Timestamper implements Runnable {
private final List<UpdateListener> _listeners;
private int _queryFrequency;
private int _concurringServers;
private int _consecutiveFails;
private volatile boolean _disabled;
private boolean _daemon;
private boolean _initialized;
@ -34,6 +35,7 @@ public class Timestamper implements Runnable {
private static final String DEFAULT_DISABLED = "true";
/** how many times do we have to query if we are changing the clock? */
private static final int DEFAULT_CONCURRING_SERVERS = 3;
private static final int MAX_CONSECUTIVE_FAILS = 10;
public static final String PROP_QUERY_FREQUENCY = "time.queryFrequencyMs";
public static final String PROP_SERVER_LIST = "time.sntpServerList";
@ -106,7 +108,7 @@ public class Timestamper implements Runnable {
}
public UpdateListener getListener(int index) {
synchronized (_listeners) {
return (UpdateListener)_listeners.get(index);
return _listeners.get(index);
}
}
@ -171,8 +173,12 @@ public class Timestamper implements Runnable {
synchronized (this) { notifyAll(); }
long sleepTime;
if (lastFailed) {
sleepTime = 30*1000;
if (++_consecutiveFails >= MAX_CONSECUTIVE_FAILS)
sleepTime = 30*60*1000;
else
sleepTime = 30*1000;
} else {
_consecutiveFails = 0;
sleepTime = _context.random().nextInt(_queryFrequency) + _queryFrequency;
if (_wellSynced)
sleepTime *= 3;
@ -191,6 +197,7 @@ public class Timestamper implements Runnable {
private boolean queryTime(String serverList[]) throws IllegalArgumentException {
long found[] = new long[_concurringServers];
long now = -1;
int stratum = -1;
long expectedDelta = 0;
_wellSynced = false;
for (int i = 0; i < _concurringServers; i++) {
@ -198,7 +205,9 @@ public class Timestamper implements Runnable {
// this delays startup when net is disconnected or the timeserver list is bad, don't make it too long
try { Thread.sleep(2*1000); } catch (InterruptedException ie) {}
}
now = NtpClient.currentTime(serverList);
long[] timeAndStratum = NtpClient.currentTimeAndStratum(serverList);
now = timeAndStratum[0];
stratum = (int) timeAndStratum[1];
long delta = now - _context.clock().now();
found[i] = delta;
if (i == 0) {
@ -230,7 +239,7 @@ public class Timestamper implements Runnable {
}
}
}
stampTime(now);
stampTime(now, stratum);
if (_log.shouldLog(Log.DEBUG)) {
StringBuilder buf = new StringBuilder(64);
buf.append("Deltas: ");
@ -242,14 +251,14 @@ public class Timestamper implements Runnable {
}
/**
* Send an HTTP request to a given URL specifying the current time
* Notify the listeners
*/
private void stampTime(long now) {
private void stampTime(long now, int stratum) {
long before = _context.clock().now();
synchronized (_listeners) {
for (int i = 0; i < _listeners.size(); i++) {
UpdateListener lsnr = (UpdateListener)_listeners.get(i);
lsnr.setNow(now);
UpdateListener lsnr = _listeners.get(i);
lsnr.setNow(now, stratum);
}
}
if (_log.shouldLog(Log.DEBUG))
@ -311,13 +320,16 @@ public class Timestamper implements Runnable {
/**
* Interface to receive update notifications for when we query the time
*
* Only used by Clock.
* stratum parameter added in 0.7.12.
* If there were any users outside of the tree, this broke compatibility, sorry.
*/
public interface UpdateListener {
/**
* The time has been queried and we have a current value for 'now'
*
*/
public void setNow(long now);
/** @param stratum 1-15, 1 being the best (added in 0.7.12) */
public void setNow(long now, int stratum);
}
}

9
core/java/src/net/i2p/util/Clock.java
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@ -117,6 +117,15 @@ public class Clock implements Timestamper.UpdateListener {
setOffset(diff);
}
/**
* @param stratum ignored
* @since 0.7.12
*/
public void setNow(long realTime, int stratum) {
long diff = realTime - System.currentTimeMillis();
setOffset(diff);
}
/**
* Retrieve the current time synchronized with whatever reference clock is in
* use.