RouterClock

java.lang.Object

net.i2p.util.Clock

net.i2p.router.RouterClock

All Implemented Interfaces:: Timestamper.UpdateListener

public class RouterClockextends Clock

Alternate location for determining the time which takes into account an offset. This offset will ideally be periodically updated so as to serve as the difference between the local computer's current time and the time as known by some reference (such as an NTP synchronized clock).

RouterClock is a subclass of Clock with access to router transports. Configuration permitting, it will block clock offset changes which would increase peer clock skew.

Nested Class Summary
Nested Classes
Modifier and Type
Class
Description
static interface
RouterClock.ClockShiftListener
Listener interface for receiving notifications when the router clock shifts.
Nested classes/interfaces inherited from class Clock
Clock.ClockUpdateListener
Modifier and Type
Class
Description
static interface
Clock.ClockUpdateListener
Listener for clock offset changes.
Field Summary
Modifier and Type
Field
Description
private long
_desiredOffset
The clock offset being sought.
private long
_lastChanged
Use system time for this.
private long
_lastProposedOffset
The offset of the last proposal.
private long
_lastShiftNanos
When the clock was last shifted.
private long
_lastSlewed
When the clock was last slewed.
private int
_lastStratum
The stratum of the last proposal.
private final Set<RouterClock.ClockShiftListener>
_shiftListeners
The listeners for clock shifts.
private final RouterTimestamper
_timeStamper
The timestamper making the proposals.
static final int
DEFAULT_STRATUM
NTP stratum assumed before any external time source is known.
private static final long
MASSIVE_SHIFT_BACKWARD
Backward shift that counts as massive.
private static final long
MASSIVE_SHIFT_FORWARD
If the system clock shifts by this much, call the callback, we probably need a soft restart.
private static final long
MAX_SLEW
How often we will slew the clock i.e.
private static final long
MIN_DELAY_FOR_WORSE_STRATUM
The max NTP Timestamper delay is 30m right now, make this longer than that.
private static final String
PROP_DISABLE_ADJUSTMENT
Testing only - disables clock adjustment when set.
private static final int
WORST_STRATUM
Worst NTP stratum accepted.
Fields inherited from class Clock
_alreadyChanged, _context, _isSystemClockBad, _offset, _startedOn, _statCreated, MAX_LIVE_OFFSET, MAX_OFFSET, MIN_OFFSET_CHANGE
Modifier and Type
Field
Description
protected boolean
_alreadyChanged
Whether the offset has ever been changed.
protected final I2PAppContext
_context
The I2P application context.
protected final boolean
_isSystemClockBad
Whether the system clock was determined to be invalid at startup.
protected long
_offset
The current offset from system time.
protected long
_startedOn
The time when this clock was started.
protected boolean
_statCreated
Whether the clock skew stat has been created.
static final long
MAX_LIVE_OFFSET
After we've started up and shifted the clock, don't allow shifts of more than 10 minutes.
static final long
MAX_OFFSET
If the clock is skewed by 3+ days, forget it.
static final long
MIN_OFFSET_CHANGE
If the clock skew changes by less than this, ignore the update (so we don't slide all over the place).
Constructor Summary
Constructors
Constructor
Description
RouterClock(RouterContext context)
Does not start.
Method Summary
Modifier and Type
Method
Description
void
addShiftListener(RouterClock.ClockShiftListener lsnr)
Add a listener to be notified of massive system clock shifts.
Timestamper
getTimestamper()
The timestamper used for time synchronization.
private void
notifyMassive(long shift)
Notifies the listeners of a massive shift.
long
now()
Retrieve the current time synchronized with whatever reference clock is in use.
void
removeShiftListener(RouterClock.ClockShiftListener lsnr)
Remove a clock shift listener.
void
setNow(long realTime, int stratum)
The current time, used by the timestamper when synchronizing.
void
setOffset(long offsetMs, boolean force)
Specify how far away from the "correct" time the computer is - a positive value means that the system time is slow, while a negative value means the system time is fast.
private void
setOffset(long offsetMs, boolean force, int stratum)
The offset, optionally forcing the change.
private void
setOffset(long offsetMs, int stratum)
The offset with the given stratum.
void
start()
Start the router clock and its associated timestamper.
Methods inherited from class Clock
addUpdateListener, fireOffsetChanged, getInstance, getLog, getOffset, getUpdatedSuccessfully, removeUpdateListener, setNow, setOffset
Modifier and Type
Method
Description
void
addUpdateListener(Clock.ClockUpdateListener lsnr)
Register a listener for clock offset changes.
protected void
fireOffsetChanged(long delta)
Notify registered listeners of a clock offset change.
static Clock
getInstance()
Shared clock for code without a router context.
protected Log
getLog()
Fetch the log on demand to avoid circular dependencies (logging uses the clock).
long
getOffset()
Current offset from system time.
boolean
getUpdatedSuccessfully()
Check whether the offset has been updated at least once.
void
removeUpdateListener(Clock.ClockUpdateListener lsnr)
Unregister a listener for clock offset changes.
void
setNow(long realTime)
Adjust the clock to the given real time, computing the offset.
void
setOffset(long offsetMs)
Specify how far away from the "correct" time the computer is - a positive value means that the system time is slow, while a negative value means the system time is fast.
Methods inherited from class Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details
- MAX_SLEW
  private static final long MAX_SLEW
  How often we will slew the clock i.e. ppm = 1000000/MAX_SLEW We should be able to slew really fast, this is probably a lot faster than what NTP does 1/50 is 12s in a 10m tunnel lifetime, that should be fine. All of this is @since 0.7.12.
  See Also:
  Constant Field Values
- DEFAULT_STRATUM
  public static final int DEFAULT_STRATUM
  NTP stratum assumed before any external time source is known.
  See Also:
  Constant Field Values
- WORST_STRATUM
  private static final int WORST_STRATUM
  Worst NTP stratum accepted.
  See Also:
  Constant Field Values
- MIN_DELAY_FOR_WORSE_STRATUM
  private static final long MIN_DELAY_FOR_WORSE_STRATUM
  The max NTP Timestamper delay is 30m right now, make this longer than that.
  See Also:
  Constant Field Values
- _desiredOffset
  private volatile long _desiredOffset
  The clock offset being sought.
- _lastSlewed
  private volatile long _lastSlewed
  When the clock was last slewed.
- _lastChanged
  private long _lastChanged
  Use system time for this.
- _lastStratum
  private int _lastStratum
  The stratum of the last proposal.
- _lastProposedOffset
  private long _lastProposedOffset
  The offset of the last proposal.
- _timeStamper
  private final RouterTimestamper _timeStamper
  The timestamper making the proposals.
- MASSIVE_SHIFT_FORWARD
  private static final long MASSIVE_SHIFT_FORWARD
  If the system clock shifts by this much, call the callback, we probably need a soft restart.
  See Also:
  Constant Field Values
- MASSIVE_SHIFT_BACKWARD
  private static final long MASSIVE_SHIFT_BACKWARD
  Backward shift that counts as massive.
  See Also:
  Constant Field Values
- PROP_DISABLE_ADJUSTMENT
  private static final String PROP_DISABLE_ADJUSTMENT
  Testing only - disables clock adjustment when set.
  See Also:
  Constant Field Values
- _shiftListeners
  private final Set<RouterClock.ClockShiftListener> _shiftListeners
  The listeners for clock shifts.
- _lastShiftNanos
  private volatile long _lastShiftNanos
  When the clock was last shifted.
Constructor Details
- RouterClock
  public RouterClock(RouterContext context)
  Does not start. Caller MUST call start().
  Parameters:
  context - the router context used to create the timestamper and to resolve clock settings
Method Details
- start
  public void start()
  Start the router clock and its associated timestamper. The timestamper will begin synchronizing with NTP or peer time sources.
- getTimestamper
  public Timestamper getTimestamper()
  The timestamper used for time synchronization.
  Overrides:
  getTimestamper in class Clock
  Returns:
  the RouterTimestamper instance
- setOffset
  public void setOffset(long offsetMs, boolean force)
  Specify how far away from the "correct" time the computer is - a positive value means that the system time is slow, while a negative value means the system time is fast.
  Overrides:
  setOffset in class Clock
  Parameters:
  offsetMs - the delta from System.currentTimeMillis() (NOT the delta from now())
  force - if true, bypass all sanity checks
- setOffset
  private void setOffset(long offsetMs, int stratum)
  The offset with the given stratum.
  Parameters:
  offsetMs - the delta from System.currentTimeMillis() (NOT the delta from now())
  stratum - the stratum of the time source
- setOffset
  private void setOffset(long offsetMs, boolean force, int stratum)
  The offset, optionally forcing the change.
  Parameters:
  offsetMs - the delta from System.currentTimeMillis() (NOT the delta from now())
  force - whether to bypass sanity checks
  stratum - the stratum of the time source
- setNow
  public void setNow(long realTime, int stratum)
  The current time, used by the timestamper when synchronizing.
  Specified by:
  setNow in interface Timestamper.UpdateListener
  Overrides:
  setNow in class Clock
  Parameters:
  realTime - the current time from the time source
  stratum - the stratum level
- now
  public long now()
  Retrieve the current time synchronized with whatever reference clock is in use. Do really simple clock slewing, like NTP but without jitter prevention. Slew the clock toward the desired offset, but only up to a maximum slew rate, and never let the clock go backwards because of slewing.
  Take care to only access the volatile variables once for speed and to avoid having another thread change them
  This is called about a zillion times a second, so we can do the slewing right here rather than in some separate thread to keep it simple. Avoiding backwards clocks when updating in a thread would be hard too.
  Overrides:
  now in class Clock
  Returns:
  the current synchronized time in milliseconds
- notifyMassive
  private void notifyMassive(long shift)
  Notifies the listeners of a massive shift.
  Parameters:
  shift - the size of the shift, in milliseconds
- addShiftListener
  public void addShiftListener(RouterClock.ClockShiftListener lsnr)
  Add a listener to be notified of massive system clock shifts. These are shifts of one minute or more.
  Parameters:
  lsnr - the listener to add
- removeShiftListener
  public void removeShiftListener(RouterClock.ClockShiftListener lsnr)
  Remove a clock shift listener.
  Parameters:
  lsnr - the listener to remove

Nested Class Summary

Nested classes/interfaces inherited from class Clock

Field Summary

Fields inherited from class Clock

Constructor Summary

Method Summary

Methods inherited from class Clock

Methods inherited from class Object

Field Details

MAX_SLEW

DEFAULT_STRATUM

WORST_STRATUM

MIN_DELAY_FOR_WORSE_STRATUM

_desiredOffset

_lastSlewed

_lastChanged

_lastStratum

_lastProposedOffset

_timeStamper

MASSIVE_SHIFT_FORWARD

MASSIVE_SHIFT_BACKWARD

PROP_DISABLE_ADJUSTMENT

_shiftListeners

_lastShiftNanos

Constructor Details

Method Details

start

getTimestamper

setOffset

setOffset

setOffset

setNow

now

notifyMassive

addShiftListener

removeShiftListener