org.jboss.ejb.plugins.lock
Class QueuedPessimisticEJBLock

java.lang.Object
  org.jboss.ejb.plugins.lock.BeanLockSupport
      org.jboss.ejb.plugins.lock.QueuedPessimisticEJBLock

All Implemented Interfaces:

BeanLock, BeanLockExt, org.jboss.util.deadlock.Resource

Direct Known Subclasses:

QueuedPessimisticEJBLockNoADE

public class QueuedPessimisticEJBLock
extends BeanLockSupport

This class is holds threads awaiting the transactional lock to be free in a fair FIFO transactional queue. Non-transactional threads are also put in this wait queue as well. Unlike SimplePessimisticEJBLock which notifies all threads on transaction completion, this class pops the next waiting transaction from the queue and notifies only those threads waiting associated with that transaction. This class should perform better than Simple on high contention loads. Holds all locks for entity beans, not used for stateful.

All BeanLocks have a reference count. When the reference count goes to 0, the lock is released from the id -> lock mapping. As of 04/10/2002, you can now specify in jboss.xml method attributes that define methods as read-only. read-only methods(and read-only beans) will release transactional locks at the end of the invocation. This decreases likelyhood of deadlock and increases performance. FIXME marcf: we should get solid numbers on this locking, bench in multi-thread environments We need someone with serious SUN hardware to run this lock into the ground

Version:

$Revision: 1.32.6.3 $

Author:

Marc Fleury, Bill Burke, Peter Murray

Field Summary

protected boolean	deadlockDetection A flag that disables the deadlock detection check
protected LockMonitor	lockMonitor

Fields inherited from class org.jboss.ejb.plugins.lock.BeanLockSupport

container, id, refs, synched, synchedDepth, tx, txTimeout

Constructor Summary

QueuedPessimisticEJBLock()

Method Summary

protected boolean	doSchedule(Invocation mi) doSchedule(Invocation) doSchedule implements a particular policy for scheduling the threads coming in.
void	endInvocation(Invocation mi) releaseMethodLock if we reach the count of zero it means the instance is free from threads (and reentrency) we wake up the next thread in the currentLock
void	endTransaction(Transaction transaction) Informs the lock that the given transaction has ended.
boolean	getDeadlockDetection()
protected org.jboss.ejb.plugins.lock.QueuedPessimisticEJBLock.TxLock	getTxLock(Transaction miTx)
protected boolean	isTxExpired(Transaction miTx)
protected void	nextTransaction()
void	removeRef() Decrement the reference count of this lock.
void	schedule(Invocation mi) This method implements the actual logic of the lock.
void	setContainer(Container container) set the ejb container of this lock.
void	setDeadlockDetection(boolean flag)
String	toString()
protected boolean	waitForTx(Transaction miTx, boolean trace) Wait until no other transaction is running with this lock.
void	wontSynchronize(Transaction trasaction) Signifies to the lock that the transaction will not Synchronize (Tx demarcation not seen).

Methods inherited from class org.jboss.ejb.plugins.lock.BeanLockSupport

addRef, attemptSync, getId, getRefs, getResourceHolder, getTransaction, releaseSync, setId, setTimeout, setTransaction, sync

Methods inherited from class java.lang.Object

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

Field Detail

lockMonitor

protected LockMonitor lockMonitor

deadlockDetection

protected boolean deadlockDetection

A flag that disables the deadlock detection check

Constructor Detail

QueuedPessimisticEJBLock

public QueuedPessimisticEJBLock()

Method Detail

setContainer

public void setContainer(Container container)

Description copied from interface: BeanLock

set the ejb container of this lock.

Specified by:

setContainer in interface BeanLock

Overrides:

setContainer in class BeanLockSupport

getDeadlockDetection

public boolean getDeadlockDetection()

setDeadlockDetection

public void setDeadlockDetection(boolean flag)

getTxLock

protected org.jboss.ejb.plugins.lock.QueuedPessimisticEJBLock.TxLock getTxLock(Transaction miTx)

isTxExpired

protected boolean isTxExpired(Transaction miTx)
                       throws Exception

Throws:

Exception

schedule

public void schedule(Invocation mi)
              throws Exception

Description copied from interface: BeanLock

This method implements the actual logic of the lock. In the case of an EJB lock it must at least implement the serialization of calls

Specified by:

schedule in interface BeanLock

Specified by:

schedule in class BeanLockSupport

Parameters:

mi - The method invocation that needs a lock.

Throws:

Exception

doSchedule

protected boolean doSchedule(Invocation mi)
                      throws Exception

doSchedule(Invocation) doSchedule implements a particular policy for scheduling the threads coming in. There is always the spec required "serialization" but we can add custom scheduling in here Synchronizing on lock: a failure to get scheduled must result in a wait() call and a release of the lock. Schedulation must return with lock.

Throws:

Exception

waitForTx

protected boolean waitForTx(Transaction miTx,
                            boolean trace)
                     throws Exception

Wait until no other transaction is running with this lock.

Returns:

Returns true if this thread was scheduled in txWaitQueue

Throws:

Exception

nextTransaction

protected void nextTransaction()

endTransaction

public void endTransaction(Transaction transaction)

Description copied from interface: BeanLock

Informs the lock that the given transaction has ended.

Specified by:

endTransaction in interface BeanLock

Specified by:

endTransaction in class BeanLockSupport

Parameters:

transaction - The transaction that has ended.

wontSynchronize

public void wontSynchronize(Transaction trasaction)

Description copied from interface: BeanLock

Signifies to the lock that the transaction will not Synchronize (Tx demarcation not seen).

OSH: This method does not seem to be called from anywhere. What is it meant for? To be called on a timeout before the transaction has terminated?

Specified by:

wontSynchronize in interface BeanLock

Specified by:

wontSynchronize in class BeanLockSupport

endInvocation

public void endInvocation(Invocation mi)

releaseMethodLock if we reach the count of zero it means the instance is free from threads (and reentrency) we wake up the next thread in the currentLock

Specified by:

endInvocation in interface BeanLock

Specified by:

endInvocation in class BeanLockSupport

removeRef

public void removeRef()

Description copied from interface: BeanLock

Decrement the reference count of this lock.

Specified by:

removeRef in interface BeanLock

Overrides:

removeRef in class BeanLockSupport

toString

public String toString()

Overrides:

toString in class Object