When using `find` to SELECT - FOR UPDATE NOWAIT, no exception is ever returned to the blocked thread, and it hangs.
The original test was in Spring Data JPA (see https://jira.spring.io/browse/DATAJPA-1259): I've tried my best to paraphase the test into straight Hibernate, but I don't have access to the tools here so there might be some bugs.
{code:java}
entityManager.find(ActivationLock.class, key, LockModeType.PESSIMISTIC_WRITE, Collections.singletonMap("javax.persistence.lock.timeout", 0));
{code}
where the full test is
{code:java}
@Entity
@Table(name = "CONF_ACTIVATION_LOCK")
public class ActivationLock {
@EmbeddedId
ActivationLockKey key;
... Getters, setters, equals
}
{code}
{code:java}
@Embeddable
public class ActivationLockKey implements Serializable {
private Long configId;
@Convert(converter = NetworkConverter.class) // Writes only the first char of the string
private NetworkEnum network
... Getters, setters, equals...
}
{code}
{code:java}
@Component // Config is on the abstract test, enables transaction management and scans this package for components
public class ActivationLockTest extends AbstractOracleDrivenUnitTests {
@PersistenceContext EntityManager underTest;
@Test
public void testFindAll() throws Exception {
ActivationLockKey key = new ActivationLockKey(42L, NetworkEnum.PRODUCTION);
ActivationLock requested = new ActivationLock(key);
if(!underTest.exists(key)){
initRow(requested);
}
AtomicBoolean ready = new AtomicBoolean(false);
AtomicBoolean contended = new AtomicBoolean(false);
AtomicBoolean done = new AtomicBoolean(false);
new Thread(() -> lockRows(requested, ready, contended, done)).start();
new Thread(() -> contendRows(requested, ready, contended)).start();
Awaitility.await().atMost(20, TimeUnit.SECONDS).until(done::get);
}
@Transactional
public void initRow(ActivationLock requested) {
ActivationLock created = underTest.persist(requested.getKey());
assertEquals(created, requested);
}
@Transactional
public void contendRows(ActivationLock requested, AtomicBoolean ready, AtomicBoolean contended) {
Awaitility.await().until(ready::get);
try {
List<ActivationLock> lockedRows = underTest.find(ActivationLock.class, requested.getKey(), LockModeType.PESSIMISTIC_WRITE, Collections.singletonMap("javax.persistence.lock.timeout", 0)); //This thread gets stuck here
//Should have thrown an exception by now
assertNull(lockedRows); // Did we just get null instead of an exception?
fail();
}
catch (Exception e){
System.out.println("Failed");
//Good! What did we get?
e.printStackTrace();
}
contended.set(true);
}
@Transactional
public void lockRows(ActivationLock requested, AtomicBoolean ready, AtomicBoolean contended, AtomicBoolean done) {
List<ActivationLock> lockedRows = underTest.find(ActivationLock.class, requested.getKey(), LockModeType.PESSIMISTIC_WRITE, Collections.singletonMap("javax.persistence.lock.timeout", 0));
assertEquals(lockedRows.get(0), requested);
ready.set(true);
Awaitility.await().until(contended::get); //This thread waits forever here
done.set(true);
}
}
{code}
The code issues the SQL I would expect, I see this SQL twice in the logs
{noformat}
Hibernate:
select
CONFIG_ID
from
CONF_ACTIVATION_LOCK
where
CONFIG_ID =?
and NETWORK =? for update
nowait
{noformat}
I would except some kind of exception, but in fact we just deadlock where I marked, and Awaitility kills the test after the timeout.
Please let me know if you need more details! |
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