Package me.ahoo.cosid.machine

Class MachineIdLease

java.lang.Object

me.ahoo.cosid.machine.MachineIdLease

public final class MachineIdLease
extends Object

The local view of how long this instance may keep using its machine id.

Other instances may take a machine id over once its owner has not renewed it for safeGuardDuration. The lease is therefore valid until the start of the last successful renewal plus safeGuardDuration, minus a margin for clock skew between hosts. Generators check it before every id, so an instance that cannot renew its lease stops generating ids before another instance can reuse the machine id.

Thread-safe; isValid(long) is a pair of volatile reads.

Field Summary

Fields

Modifier and Type	Field	Description
static final MachineIdLease	FOREVER	A lease that never expires, used when machine ids are never recycled.
static final Duration	MAX_CLOCK_SKEW_MARGIN	Upper bound of the clock skew margin.

Constructor Summary

Constructors

Constructor	Description
MachineIdLease(@Nullable String namespace, @Nullable InstanceId instanceId, Duration safeGuardDuration)

Method Summary

Modifier and Type	Method	Description
void	ensureValid()	Throw MachineIdLostException if the lease is lost or expired.
long	getValidUntil()
boolean	isLost()
boolean	isReleased()
boolean	isValid(long now)
void	markLost()	The remote store reported that the machine id now belongs to another instance.
void	markReleased()	The machine id is about to be reverted on shutdown.
void	renew(long renewedAt)	Extend the lease after a successful distribute or guard.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

MAX_CLOCK_SKEW_MARGIN

public static final Duration MAX_CLOCK_SKEW_MARGIN

Upper bound of the clock skew margin.

FOREVER

public static final MachineIdLease FOREVER

A lease that never expires, used when machine ids are never recycled.

Constructor Details

MachineIdLease

public MachineIdLease(@Nullable String namespace,
 @Nullable InstanceId instanceId,
 Duration safeGuardDuration)

Method Details

renew

public void renew(long renewedAt)

Extend the lease after a successful distribute or guard.

Parameters:

renewedAt - the time, in milliseconds, at which the renewal request was started

markLost

public void markLost()

The remote store reported that the machine id now belongs to another instance. The lease never becomes valid again.

isLost

public boolean isLost()

markReleased

public void markReleased()

The machine id is about to be reverted on shutdown. The lease never becomes valid again, so no id is generated with a machine id that another instance may already have taken.

isReleased

public boolean isReleased()

getValidUntil

public long getValidUntil()

isValid

public boolean isValid(long now)

ensureValid

public void ensureValid()
                 throws MachineIdLostException

Throw MachineIdLostException if the lease is lost or expired.

Throws:

MachineIdLostException

toString

public String toString()

Overrides:

toString in class Object