Hi,
I played little bit around with the tree cache using the optimistic locking
scheme. I wrote a small unit tests (s.b.), which tries to modify the same node
at the same time by different threads in different transactions. At the first
view, it looks like, that everything works fine. But running the test multiple
times showed, that sometimes an IllegalStateException instead of CacheException
on commiting the transaction will be thrown:
| java.lang.RuntimeException:
| at
org.jboss.cache.interceptors.TxInterceptor$LocalSynchronizationHandler.beforeCompletion(TxInterceptor.java:1091)
| at
org.jboss.cache.interceptors.OrderedSynchronizationHandler.beforeCompletion(OrderedSynchronizationHandler.java:75)
| at
org.objectweb.jotm.SubCoordinator.doBeforeCompletion(SubCoordinator.java:1487)
| at
org.objectweb.jotm.SubCoordinator.commit_one_phase(SubCoordinator.java:416)
| at org.objectweb.jotm.TransactionImpl.commit(TransactionImpl.java:239)
| at
de.gameduell.server.cache.PureOptimisticLockingTest$Worker.run(PureOptimisticLockingTest.java:137)
| Caused by: java.lang.IllegalStateException: there is already a writer
holding the lock: GlobalTransaction:<null>:41
| at org.jboss.cache.lock.LockMap.setWriterIfNotNull(LockMap.java:96)
| at
org.jboss.cache.lock.IdentityLock.acquireWriteLock(IdentityLock.java:204)
| at org.jboss.cache.Node.acquireWriteLock(Node.java:431)
| at org.jboss.cache.Node.acquire(Node.java:386)
| at
org.jboss.cache.interceptors.OptimisticLockingInterceptor.lockNodes(OptimisticLockingInterceptor.java:149)
| at
org.jboss.cache.interceptors.OptimisticLockingInterceptor.invoke(OptimisticLockingInterceptor.java:76)
| at org.jboss.cache.interceptors.Interceptor.invoke(Interceptor.java:68)
| at
org.jboss.cache.interceptors.TxInterceptor.runPreparePhase(TxInterceptor.java:804)
| at
org.jboss.cache.interceptors.TxInterceptor$LocalSynchronizationHandler.beforeCompletion(TxInterceptor.java:1069)
| ... 5 more
Running the TreeCache I used JBossCache 1.4.0.GA and JOTM 2.0.10 with the
following cache-config:
<?xml version="1.0" encoding="UTF-8"?>
| <server>
| <mbean code="org.jboss.cache.TreeCache"
name="jboss.cache:service=TreeCache">
| <attribute name="NodeLockingScheme">OPTIMISTIC</attribute>
| <attribute name="CacheMode">LOCAL</attribute>
| </mbean>
| </server>
|
|
That's my JUnit-Test:
| import javax.transaction.Transaction;
| import javax.transaction.TransactionManager;
|
| import junit.framework.TestCase;
|
| import org.jboss.cache.CacheException;
| import org.jboss.cache.PropertyConfigurator;
| import org.jboss.cache.TransactionManagerLookup;
| import org.jboss.cache.TreeCache;
| import org.objectweb.jotm.Current;
|
| import EDU.oswego.cs.dl.util.concurrent.CyclicBarrier;
|
|
| /**
| * OptimisticLockingTest
| */
| public class OptimisticLockingTest extends TestCase {
|
| private static final String NODE_PATH = "/path/node";
| private static final String KEY = "key";
|
| private static final Current jotm = new Current();
|
| private TreeCache cache;
|
| protected void setUp() throws Exception {
| super.setUp();
|
| cache = new TreeCache();
| final PropertyConfigurator config = new PropertyConfigurator();
| cache.setTransactionManagerLookup(new
TransactionManagerLookup() {
| public TransactionManager getTransactionManager()
throws Exception {
| return Current.getTransactionManager();
| }
| });
| config.configure(cache, this.getClass().getResourceAsStream(
| "/cache-config.xml"));
| cache.startService();
| }
|
| public void testSimultanWrite() throws Exception {
| for (int i = 2; i < 20; i++) {
| System.out.println(">> testing simultaneous writes with
" + i
| + " threads...");
| testSimultanWrite(i);
| }
| }
|
| public void testSimultanWrite(final int _numThreads)
| throws Exception {
| final CyclicBarrier barrier = new
CyclicBarrier(_numThreads);
|
| Worker[] workers = new Worker[_numThreads];
| for (int i = 0; i < workers.length; i++) {
| workers = new Worker();
| workers.barrier = barrier;
| workers.value = "worker" + i;
| if (i == 0) {
| workers.isMaster = true;
| }
| workers.start();
| }
|
| for (int i = 0; i < workers.length; i++) {
| workers.join();
| }
|
| assertNull(workers[0].exception);
|
| for (int i = 0; i < workers.length; i++) {
| assertNull("rollback failed",
workers.rollbackException);
| }
|
| for (int i = 1; i < workers.length; i++) {
| assertNotNull("missing exception", workers.exception);
| assertTrue("exception is not of type CacheException",
| workers.exception.getCause() instanceof
CacheException);
| }
| assertEquals("worker0", cache.get(NODE_PATH, KEY));
|
| cache.getTransactionManager().begin();
| cache.remove(NODE_PATH);
| cache.getTransactionManager().commit();
| }
|
| private class Worker extends Thread {
|
| private CyclicBarrier barrier;
| private Exception exception;
| private Exception rollbackException;
| private String value;
| private boolean isMaster;
|
| /**
| * @see java.lang.Thread#run()
| */
| public void run() {
|
| final TransactionManager txManager =
cache.getTransactionManager();
|
| Transaction tx = null;
| try {
| // wait for all threads started
| barrier.barrier();
|
| if (isMaster) {
| txManager.begin();
| cache.put(NODE_PATH, KEY, value);
|
| // lets the other threads start writing
| barrier.barrier();
|
| // wait for other threads to their
modification
| barrier.barrier();
|
| // commit first
| tx = txManager.getTransaction();
| tx.commit();
|
| // lets the other threads commit
| barrier.barrier();
| } else {
| // wait for master to start transaction
| barrier.barrier();
|
| txManager.begin();
| cache.put(NODE_PATH, KEY, value);
|
| // signal modification
| barrier.barrier();
|
| // wait for master to commit transaction
| barrier.barrier();
| tx = txManager.getTransaction();
| tx.commit();
| }
| } catch (Exception e) {
| exception = e;
| try {
| tx.rollback();
| } catch (Exception e1) {
| rollbackException = e1;
| }
| }
| }
| }
| }
|
|
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