org.apache.hadoop.hbase.procedure2

Class LockAndQueue

java.lang.Object

java.util.AbstractCollection<E>

java.util.ArrayDeque<Procedure>

org.apache.hadoop.hbase.procedure2.ProcedureDeque

org.apache.hadoop.hbase.procedure2.LockAndQueue

All Implemented Interfaces:

Serializable, Cloneable, Iterable<Procedure>, Collection<Procedure>, Deque<Procedure>, Queue<Procedure>, LockStatus

@InterfaceAudience.Private
public class LockAndQueue
extends ProcedureDeque
implements LockStatus

Locking for mutual exclusion between procedures. Used only by procedure framework internally. LockAndQueue has two purposes:

1. Acquire/release exclusive/shared locks.
2. Maintains a list of procedures waiting on this lock. LockAndQueue extends ProcedureDeque class. Blocked Procedures are added to our super Deque. Using inheritance over composition to keep the Deque of waiting Procedures is unusual, but we do it this way because in certain cases, there will be millions of regions. This layout uses less memory.

NOT thread-safe. Needs external concurrency control: e.g. uses in MasterProcedureScheduler are guarded by schedLock().
There is no need of 'volatile' keyword for member variables because of memory synchronization guarantees of locks (see 'Memory Synchronization', http://docs.oracle.com/javase/8/docs/api/java/util/concurrent/locks/Lock.html)
We do not implement Lock interface because we need exclusive and shared locking, and also because try-lock functions require procedure id.
We do not use ReentrantReadWriteLock directly because of its high memory overhead.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
LockAndQueue()

Method Summary

Modifier and Type	Method and Description
Procedure<?>	getExclusiveLockOwnerProcedure()
long	getExclusiveLockProcIdOwner()
int	getSharedLockCount()
boolean	hasExclusiveLock()
boolean	hasLockAccess(Procedure proc)
boolean	hasParentLock(Procedure proc)
boolean	isLocked()
boolean	isLockOwner(long procId)
boolean	releaseExclusiveLock(Procedure proc)
boolean	releaseSharedLock()
String	toString()
boolean	tryExclusiveLock(Procedure proc)
boolean	trySharedLock()

Methods inherited from class java.util.ArrayDeque

add, addFirst, addLast, clear, clone, contains, descendingIterator, element, getFirst, getLast, isEmpty, iterator, offer, offerFirst, offerLast, peek, peekFirst, peekLast, poll, pollFirst, pollLast, pop, push, remove, remove, removeFirst, removeFirstOccurrence, removeLast, removeLastOccurrence, size, spliterator, toArray, toArray

Methods inherited from class java.util.AbstractCollection

addAll, containsAll, removeAll, retainAll

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Collection

addAll, containsAll, equals, hashCode, parallelStream, removeAll, removeIf, retainAll, stream

Methods inherited from interface java.lang.Iterable

forEach

Constructor Detail

LockAndQueue

public LockAndQueue()

Method Detail

isLocked

public boolean isLocked()

Specified by:

isLocked in interface LockStatus

hasExclusiveLock

public boolean hasExclusiveLock()

Specified by:

hasExclusiveLock in interface LockStatus

isLockOwner

public boolean isLockOwner(long procId)

Specified by:

isLockOwner in interface LockStatus

hasParentLock

public boolean hasParentLock(Procedure proc)

Specified by:

hasParentLock in interface LockStatus

hasLockAccess

public boolean hasLockAccess(Procedure proc)

Specified by:

hasLockAccess in interface LockStatus

getExclusiveLockOwnerProcedure

public Procedure<?> getExclusiveLockOwnerProcedure()

Specified by:

getExclusiveLockOwnerProcedure in interface LockStatus

getExclusiveLockProcIdOwner

public long getExclusiveLockProcIdOwner()

Specified by:

getExclusiveLockProcIdOwner in interface LockStatus

getSharedLockCount

public int getSharedLockCount()

Specified by:

getSharedLockCount in interface LockStatus

trySharedLock

public boolean trySharedLock()

releaseSharedLock

public boolean releaseSharedLock()

tryExclusiveLock

public boolean tryExclusiveLock(Procedure proc)

releaseExclusiveLock

public boolean releaseExclusiveLock(Procedure proc)

Returns:

True if we released a lock.

toString

public String toString()

Overrides:

toString in class AbstractCollection<Procedure>