com.hazelcast.core

Interface ILock

All Superinterfaces:

DistributedObject, Lock

All Known Implementing Classes:

ClientLockProxy, LockProxy

Deprecated.

Please use FencedLock instead. This interface will be removed in Hazelcast 4.0.

@Deprecated
public interface ILock
extends Lock, DistributedObject

Distributed implementation of Lock.

Example

     Lock mylock = Hazelcast.getLock(mylockobject); mylock.lock();
 try {
      // do something
 } finally {
      mylock.unlock();
 }
 //Lock on Map
      IMap map = Hazelcast.getMap("customers"); map.lock("1");
 try {
      // do something
 } finally {
 map.unlock("1"); }
 

Behaviour of ILock under split-brain scenarios should be taken into account when using this data structure. During a split, each partitioned cluster will either create a brand new and un-acquired ILock or it will continue to use the primary or back-up version. As the acquirer of the ILock might reside in a different partitioned network this can lead to situations where the lock is never obtainable.

When the split heals, Hazelcast performs a default largest cluster wins resolution. Where the clusters are the same size a winner of the merge will be randomly chosen. In any case, this can lead to situations where (post-merge) multiple acquirers think they hold the same lock, when in fact the ILock itself records only one owner. When the false owners come to release the ILock an IllegalMonitorStateException is thrown.

Acquiring an ILock with a lease time lock(long, TimeUnit) can help to mitigate such scenarios.

As a defensive mechanism against such inconsistency, consider using the in-built split-brain protection for lock. Using this functionality it is possible to restrict operations in smaller partitioned clusters. It should be noted that there is still an inconsistency window between the time of the split and the actual detection. Therefore using this reduces the window of inconsistency but can never completely eliminate it.

See Also:

Lock, FencedLock

Method Summary

Modifier and Type	Method and Description
void	forceUnlock() Deprecated. Releases the lock regardless of the lock owner.
Object	getKey() Deprecated. use DistributedObject.getName() instead.
int	getLockCount() Deprecated. Returns re-entrant lock hold count, regardless of lock ownership.
long	getRemainingLeaseTime() Deprecated. Returns remaining lease time in milliseconds.
boolean	isLocked() Deprecated. Returns whether this lock is locked or not.
boolean	isLockedByCurrentThread() Deprecated. Returns whether this lock is locked by current thread or not.
void	lock() Deprecated.
void	lock(long leaseTime, TimeUnit timeUnit) Deprecated. Acquires the lock for the specified lease time.
Condition	newCondition() Deprecated. This method is not implemented! Use newCondition(String) instead.
ICondition	newCondition(String name) Deprecated. Returns a new ICondition instance that is bound to this ILock instance with given name.
boolean	tryLock() Deprecated.
boolean	tryLock(long time, TimeUnit unit) Deprecated.
boolean	tryLock(long time, TimeUnit unit, long leaseTime, TimeUnit leaseUnit) Deprecated. Tries to acquire the lock for the specified lease time.
void	unlock() Deprecated. Releases the lock.

Methods inherited from interface java.util.concurrent.locks.Lock

lockInterruptibly

Methods inherited from interface com.hazelcast.core.DistributedObject

destroy, getName, getPartitionKey, getServiceName

Method Detail

getKey

@Deprecated
Object getKey()

Deprecated. use DistributedObject.getName() instead.

Returns the lock object, the key for this lock instance.

Returns:

lock object.

lock

void lock()

Deprecated.

Specified by:

lock in interface Lock

tryLock

boolean tryLock()

Deprecated.

Specified by:

tryLock in interface Lock

tryLock

boolean tryLock(long time,
                TimeUnit unit)
         throws InterruptedException

Deprecated.

Specified by:

tryLock in interface Lock

Throws:

InterruptedException

tryLock

boolean tryLock(long time,
                TimeUnit unit,
                long leaseTime,
                TimeUnit leaseUnit)
         throws InterruptedException

Deprecated.

Tries to acquire the lock for the specified lease time.

After lease time, the lock will be released.

If the lock is not available, then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of two things happens:

• the lock is acquired by the current thread, or
• the specified waiting time elapses.

Parameters:

time - maximum time to wait for the lock.

unit - time unit of the time argument.

leaseTime - time to wait before releasing the lock.

leaseUnit - unit of time to specify lease time.

Returns:

true if the lock was acquired and false if the waiting time elapsed before the lock was acquired.

Throws:

InterruptedException

unlock

void unlock()

Deprecated.

Releases the lock.

Specified by:

unlock in interface Lock

lock

void lock(long leaseTime,
          TimeUnit timeUnit)

Deprecated.

Acquires the lock for the specified lease time.

After lease time, lock will be released..

If the lock is not available then the current thread becomes disabled for thread scheduling purposes and lies dormant until the lock has been acquired.

Parameters:

leaseTime - time to wait before releasing the lock.

timeUnit - unit of time for the lease time.

Throws:

IllegalMonitorStateException - if the current thread does not hold this lock

forceUnlock

void forceUnlock()

Deprecated.

Releases the lock regardless of the lock owner. It always successfully unlocks, never blocks, and returns immediately.

newCondition

Condition newCondition()

Deprecated.

This method is not implemented! Use newCondition(String) instead.

Specified by:

newCondition in interface Lock

Throws:

UnsupportedOperationException - the exception is always thrown, since this method is not implemented

newCondition

ICondition newCondition(String name)

Deprecated.

Returns a new ICondition instance that is bound to this ILock instance with given name.

Before waiting on the condition the lock must be held by the current thread. A call to Condition.await() will atomically release the lock before waiting and re-acquire the lock before the wait returns.

Parameters:

name - identifier of the new condition instance

Returns:

A new ICondition instance for this ILock instance

Throws:

NullPointerException - if name is null.

isLocked

boolean isLocked()

Deprecated.

Returns whether this lock is locked or not.

Returns:

true if this lock is locked, false otherwise.

isLockedByCurrentThread

boolean isLockedByCurrentThread()

Deprecated.

Returns whether this lock is locked by current thread or not.

Returns:

true if this lock is locked by current thread, false otherwise.

getLockCount

int getLockCount()

Deprecated.

Returns re-entrant lock hold count, regardless of lock ownership.

Returns:

the lock hold count.

getRemainingLeaseTime

long getRemainingLeaseTime()

Deprecated.

Returns remaining lease time in milliseconds. If the lock is not locked then -1 will be returned.

Returns:

remaining lease time in milliseconds.