Module dk.cloudcreate.essentials.components.foundation

Package dk.cloudcreate.essentials.components.foundation.fencedlock

Interface FencedLock

All Superinterfaces:

AutoCloseable

All Known Implementing Classes:

DBFencedLock

public interface FencedLock
extends AutoCloseable

Represents a named fenced lock, where the getCurrentToken() can be passed on to down stream logic, which can keep track of the token value to identify if a timed out lock is being used to request logic.
The fence locking concept is described here https://martin.kleppmann.com/2016/02/08/how-to-do-distributed-locking.html

Method Summary

Modifier and Type	Method	Description
default void	close()	Closing a FencedLock will automatically call release()
Long	getCurrentToken()	The current token value as of the getLockLastConfirmedTimestamp() for this Lock across all FencedLockManager instances Every time a lock is acquired or confirmed a new token is issued (i.e.
OffsetDateTime	getLockAcquiredTimestamp()	At what time did the JVM/FencedLockManager.getLockManagerInstanceId() that currently has acquired the lock acquire it (at first acquiring the getLockLastConfirmedTimestamp() is set to getLockAcquiredTimestamp())
String	getLockedByLockManagerInstanceId()	Which JVM/FencedLockManager.getLockManagerInstanceId() that has acquired this lock
OffsetDateTime	getLockLastConfirmedTimestamp()	At what time did the JVM/FencedLockManager.getLockManagerInstanceId(), that currently has acquired the lock, last confirm that it still has access to the lock
LockName	getName()	The name of the Lock
boolean	isLocked()	Is this lock locked?
boolean	isLockedByThisLockManagerInstance()	Is this Lock locked by this JVM node
void	registerCallback(LockCallback lockCallback)
void	release()	Release/Unlock the lock.

Method Details

getName

LockName getName()

The name of the Lock

Returns:

the lock name

getCurrentToken

Long getCurrentToken()

The current token value as of the getLockLastConfirmedTimestamp() for this Lock across all FencedLockManager instances
Every time a lock is acquired or confirmed a new token is issued (i.e. it's ever-growing value)

getLockedByLockManagerInstanceId

String getLockedByLockManagerInstanceId()

Which JVM/FencedLockManager.getLockManagerInstanceId() that has acquired this lock

getLockAcquiredTimestamp

OffsetDateTime getLockAcquiredTimestamp()

At what time did the JVM/FencedLockManager.getLockManagerInstanceId() that currently has acquired the lock acquire it (at first acquiring the getLockLastConfirmedTimestamp() is set to getLockAcquiredTimestamp())

getLockLastConfirmedTimestamp

OffsetDateTime getLockLastConfirmedTimestamp()

At what time did the JVM/FencedLockManager.getLockManagerInstanceId(), that currently has acquired the lock, last confirm that it still has access to the lock

isLocked

boolean isLocked()

Is this lock locked?

isLockedByThisLockManagerInstance

boolean isLockedByThisLockManagerInstance()

Is this Lock locked by this JVM node

release

void release()

Release/Unlock the lock. Only works if isLockedByThisLockManagerInstance() is true

registerCallback

void registerCallback(LockCallback lockCallback)

close

default void close()
            throws Exception

Closing a FencedLock will automatically call release()

Specified by:

close in interface AutoCloseable

Throws:

Exception