com.bigdata.concurrent

Class NonBlockingLockManager.ResourceQueue<T extends NonBlockingLockManager.LockFutureTask<? extends Object>>

java.lang.Object

com.bigdata.concurrent.NonBlockingLockManager.ResourceQueue<T>

Type Parameters:

T - The generic type of the elements in the queue.

Enclosing class:

NonBlockingLockManager<R extends Comparable<R>>

protected class NonBlockingLockManager.ResourceQueue<T extends NonBlockingLockManager.LockFutureTask<? extends Object>>
extends Object

Unbounded queue of operations waiting to gain an exclusive lock on a resource. By default, the queue imposes a "fair" schedule for access to the resource. Deadlocks among resources are detected using a WAITS_FOR graph that is shared by all resources and transactions for a given database instance.

Note: deadlock detection MAY be disabled when all lock requests are (a) pre-declared; and (b) sorted. When disabled the WAITS_FOR graph is NOT maintained.

Version:

$Id$

Author:

Bryan Thompson

See Also:

LockManager, TxDag

Constructor Summary

Constructors

Constructor and Description
NonBlockingLockManager.ResourceQueue(R resource) Create a queue of lock requests for a resource.

Method Summary

Methods

Modifier and Type	Method and Description
int	getQueueSize() The #of pending requests for a lock on the resource.
R	getResource() The resource whose locks are administeded by this object.
boolean	isGranted(T tx) Return true if the transaction currently holds the lock.
boolean	isLocked() True iff there is a granted group.
String	toString() Note: This uses LinkedBlockingQueue.toString() to serialize the state of the resource queue so the result will be consistent per the contract of that method and LinkedBlockingQueue.iterator().

Methods inherited from class java.lang.Object

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

Constructor Detail

NonBlockingLockManager.ResourceQueue

public NonBlockingLockManager.ResourceQueue(R resource)

Create a queue of lock requests for a resource.

Parameters:

resource - The resource.

Method Detail

getResource

public R getResource()

The resource whose locks are administeded by this object.

isLocked

public boolean isLocked()

True iff there is a granted group.

getQueueSize

public int getQueueSize()

The #of pending requests for a lock on the resource.

isGranted

public boolean isGranted(T tx)

Return true if the transaction currently holds the lock.

Parameters:

tx - The transaction.

toString

public String toString()

Note: This uses LinkedBlockingQueue.toString() to serialize the state of the resource queue so the result will be consistent per the contract of that method and LinkedBlockingQueue.iterator().

Overrides:

toString in class Object