Module dk.cloudcreate.essentials.components.foundation

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

Class DBFencedLockManager<UOW extends UnitOfWork,LOCK extends DBFencedLock>

java.lang.Object

dk.cloudcreate.essentials.components.foundation.fencedlock.DBFencedLockManager<UOW,LOCK>

Type Parameters:

UOW - the type of UnitOfWork required

LOCK - the concrete type of DBFencedLock used

All Implemented Interfaces:

FencedLockManager, Lifecycle

public abstract class DBFencedLockManager<UOW extends UnitOfWork,LOCK extends DBFencedLock>
extends Object
implements FencedLockManager

Common super base class for implementing persistent/durable FencedLockManager's

Field Summary

Fields

Modifier and Type	Field	Description
protected final org.slf4j.Logger	log
protected int	syncAcquireLockPauseIntervalMs	tryAcquireLock(LockName)/tryAcquireLock(LockName, Duration) and acquireLock(LockName) pause interval between retries

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	DBFencedLockManager(FencedLockStorage<UOW,LOCK> lockStorage, UnitOfWorkFactory<? extends UOW> unitOfWorkFactory, Optional<String> lockManagerInstanceId, Duration lockTimeOut, Duration lockConfirmationInterval, Optional<dk.cloudcreate.essentials.reactive.EventBus> eventBus)

Method Summary

Modifier and Type	Method	Description
FencedLock	acquireLock(LockName lockName)	Acquire the lock on this JVM Node.
void	acquireLockAsync(LockName lockName, LockCallback lockCallback)	Asynchronously try to acquire a lock by the given name and call the LockCallback.lockAcquired(FencedLock) when the lock is acquired To stop the background acquiring process, you need to call FencedLockManager.cancelAsyncLockAcquiring(LockName) with the same lockName
void	cancelAsyncLockAcquiring(LockName lockName)	Cancel a previously started asynchronous lock acquiring background process IF this JVM node had acquired a FencedLock then this lock will be released AND the LockCallback.lockReleased(FencedLock) will be called on the LockCallback instance that was supplied to the FencedLockManager.acquireLockAsync(LockName, LockCallback) Otherwise only the background lock acquiring process will be stopped.
void	deleteAllLocksInDB()
long	getInitialTokenValue()
String	getLockManagerInstanceId()	Get the instance id that distinguishes different FencedLockManager instances from each other For local JVM testing you can assign a unique instance id to allow multiple FencedLockManager's to compete for Locks. In production the hostname should be returned
Long	getUninitializedTokenValue()
boolean	isLockAcquired(LockName lockName)	Is the lock acquired
boolean	isLockAcquiredByAnotherLockManagerInstance(LockName lockName)	Is the lock already acquired by another JVM node
boolean	isLockedByThisLockManagerInstance(LockName lockName)	Is the lock already acquired by this JVM node
boolean	isStarted()	Returns true if the process is started
Optional<FencedLock>	lookupLock(LockName lockName)	Lookup a lock
protected void	notify(FencedLockEvents event)
void	pause()
protected void	releaseLock(LOCK lock)	Internal method only to be called by subclasses of DBFencedLockManager and DBFencedLock
void	resume()
void	start()	Start the processing.
void	stop()	Stop the processing.
String	toString()
Optional<FencedLock>	tryAcquireLock(LockName lockName)	Try to acquire the lock using this Lock Manager instance
Optional<FencedLock>	tryAcquireLock(LockName lockName, Duration timeout)	Try to acquire the lock on this JVM Node
protected void	usingUnitOfWork(dk.cloudcreate.essentials.shared.functional.CheckedConsumer<UOW> unitOfWorkConsumer)	Use a UnitOfWork to perform transactional changes
protected <R> R	withUnitOfWork(dk.cloudcreate.essentials.shared.functional.CheckedFunction<UOW,R> unitOfWorkFunction)	Use a UnitOfWork to perform transactional changes

Methods inherited from class java.lang.Object

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

Field Details

log

protected final org.slf4j.Logger log

syncAcquireLockPauseIntervalMs

protected int syncAcquireLockPauseIntervalMs

tryAcquireLock(LockName)/tryAcquireLock(LockName, Duration) and acquireLock(LockName) pause interval between retries

Constructor Details

DBFencedLockManager

protected DBFencedLockManager(FencedLockStorage<UOW,LOCK> lockStorage,
 UnitOfWorkFactory<? extends UOW> unitOfWorkFactory,
 Optional<String> lockManagerInstanceId,
 Duration lockTimeOut,
 Duration lockConfirmationInterval,
 Optional<dk.cloudcreate.essentials.reactive.EventBus> eventBus)

Parameters:

lockStorage - the lock storage used for the lock manager

unitOfWorkFactory - the UnitOfWork factory

lockManagerInstanceId - The unique name for this lock manager instance. If left Optional.empty() then the machines hostname is used

lockTimeOut - the period between FencedLock.getLockLastConfirmedTimestamp() and the current time before the lock is marked as timed out

lockConfirmationInterval - how often should the locks be confirmed. MUST is less than the lockTimeOut

eventBus - optional LocalEventBus where FencedLockEvents will be published

Method Details

start

public void start()

Description copied from interface: Lifecycle

Start the processing. This operation must be idempotent, such that duplicate calls to Lifecycle.start() for an already started process (where Lifecycle.isStarted() returns true) is ignored

Specified by:

start in interface Lifecycle

notify

protected void notify(FencedLockEvents event)

pause

public void pause()

resume

public void resume()

releaseLock

protected void releaseLock(LOCK lock)

Internal method only to be called by subclasses of DBFencedLockManager and DBFencedLock

Parameters:

lock - the lock to be released

lookupLock

public Optional<FencedLock> lookupLock(LockName lockName)

Description copied from interface: FencedLockManager

Lookup a lock

Specified by:

lookupLock in interface FencedLockManager

Parameters:

lockName - the name of the lock

Returns:

an Optional with the locks current state or Optional.empty() if the lock doesn't exist

stop

public void stop()

Description copied from interface: Lifecycle

Stop the processing. This operation must be idempotent, such that duplicate calls to Lifecycle.stop() for an already stopped process (where Lifecycle.isStarted() returns false) is ignored

Specified by:

stop in interface Lifecycle

isStarted

public boolean isStarted()

Description copied from interface: Lifecycle

Returns true if the process is started

Specified by:

isStarted in interface Lifecycle

Returns:

true if the process is started otherwise false

tryAcquireLock

public Optional<FencedLock> tryAcquireLock(LockName lockName)

Description copied from interface: FencedLockManager

Try to acquire the lock using this Lock Manager instance

Specified by:

tryAcquireLock in interface FencedLockManager

Parameters:

lockName - the name of the lock

Returns:

An Optional with the FencedLock IF it was acquired by the FencedLockManager on this JVM Node, otherwise it return an empty Optional

tryAcquireLock

public Optional<FencedLock> tryAcquireLock(LockName lockName,
 Duration timeout)

Description copied from interface: FencedLockManager

Try to acquire the lock on this JVM Node

Specified by:

tryAcquireLock in interface FencedLockManager

Parameters:

lockName - the name of the lock

timeout - timeout for the lock acquiring

Returns:

An Optional with the FencedLock IF it was acquired by the FencedLockManager on this JVM Node, otherwise it return an empty Optional

acquireLock

public FencedLock acquireLock(LockName lockName)

Description copied from interface: FencedLockManager

Acquire the lock on this JVM Node. If the lock already is acquired by another JVM Node, then this method will wait until the lock can be acquired by this JVM node

Specified by:

acquireLock in interface FencedLockManager

Parameters:

lockName - the name of the lock

Returns:

The FencedLock when can be acquired by this JVM Node

isLockAcquired

public boolean isLockAcquired(LockName lockName)

Description copied from interface: FencedLockManager

Is the lock acquired

Specified by:

isLockAcquired in interface FencedLockManager

Parameters:

lockName - the name of the lock

Returns:

true if the lock is acquired, otherwise false

isLockedByThisLockManagerInstance

public boolean isLockedByThisLockManagerInstance(LockName lockName)

Description copied from interface: FencedLockManager

Is the lock already acquired by this JVM node

Specified by:

isLockedByThisLockManagerInstance in interface FencedLockManager

Parameters:

lockName - the lock name

Returns:

true of the lock is acquired by this JVM node

isLockAcquiredByAnotherLockManagerInstance

public boolean isLockAcquiredByAnotherLockManagerInstance(LockName lockName)

Description copied from interface: FencedLockManager

Is the lock already acquired by another JVM node

Specified by:

isLockAcquiredByAnotherLockManagerInstance in interface FencedLockManager

Parameters:

lockName - the name of the lock

Returns:

true of the lock is acquired by this JVM node

acquireLockAsync

public void acquireLockAsync(LockName lockName,
 LockCallback lockCallback)

Description copied from interface: FencedLockManager

Asynchronously try to acquire a lock by the given name and call the LockCallback.lockAcquired(FencedLock) when the lock is acquired
To stop the background acquiring process, you need to call FencedLockManager.cancelAsyncLockAcquiring(LockName) with the same lockName

Specified by:

acquireLockAsync in interface FencedLockManager

Parameters:

lockName - the name of the lock

lockCallback - the callback that's notified when a lock is acquired

cancelAsyncLockAcquiring

public void cancelAsyncLockAcquiring(LockName lockName)

Description copied from interface: FencedLockManager

Cancel a previously started asynchronous lock acquiring background process
IF this JVM node had acquired a FencedLock then this lock will be released AND the LockCallback.lockReleased(FencedLock) will be called on the LockCallback instance that was supplied to the FencedLockManager.acquireLockAsync(LockName, LockCallback)
Otherwise only the background lock acquiring process will be stopped.

Specified by:

cancelAsyncLockAcquiring in interface FencedLockManager

Parameters:

lockName - the name of the lock

getLockManagerInstanceId

public String getLockManagerInstanceId()

Description copied from interface: FencedLockManager

Get the instance id that distinguishes different FencedLockManager instances from each other
For local JVM testing you can assign a unique instance id to allow multiple FencedLockManager's to compete for Locks.
In production the hostname should be returned

Specified by:

getLockManagerInstanceId in interface FencedLockManager

Returns:

the instance id

toString

public String toString()

Overrides:

toString in class Object

getUninitializedTokenValue

public Long getUninitializedTokenValue()

getInitialTokenValue

public long getInitialTokenValue()

deleteAllLocksInDB

public void deleteAllLocksInDB()

usingUnitOfWork

protected void usingUnitOfWork(dk.cloudcreate.essentials.shared.functional.CheckedConsumer<UOW> unitOfWorkConsumer)

Use a UnitOfWork to perform transactional changes

Parameters:

unitOfWorkConsumer - the consumer of the created UnitOfWork

withUnitOfWork

protected <R> R withUnitOfWork(dk.cloudcreate.essentials.shared.functional.CheckedFunction<UOW,R> unitOfWorkFunction)

Use a UnitOfWork to perform transactional changes

Type Parameters:

R - the return value from the unitOfWorkFunction

Parameters:

unitOfWorkFunction - The function that consumes the creatd UnitOfWork

Returns:

the result of the calling the unitOfWorkFunction