Timer event is always handled by a new instance?

[granby]

I modified the timer example so that the timer is restarted. I also kept track of instances of the statless bean:

@Stateless
@Remote(ExampleTimer.class)
public class ExampleTimerBean implements ExampleTimer
{
private static int instanceCount=0;

private @Resource SessionContext ctx;

public void scheduleTimer(long milliseconds)
{
ctx.getTimerService().createTimer(new Date(new Date().getTime() + milliseconds), "Hello World");
}

@Timeout
public void timeoutHandler(Timer timer)
{
timer.cancel();

ctx.getTimerService().createTimer(new Date(new Date().getTime() + 50), "Hello World");
}

@PostConstruct
public void postConstruct(){
instanceCount++;
System.out.println("New instance: "+instanceCount);
}

@PreDestroy
public void preDestroy(){
instanceCount++;
System.out.println("Instance removed: "+instanceCount);
}
}

I removed some lines of the output but as you can see each timeout seems to be handled by a new statless instance. How come that they never get reused?

I guess I pushed it a bit with the low timeout value but I was expecting another type of error not duplicate key?

21:37:35,218 INFO [STDOUT] New instance: 1406
21:37:35,234 INFO [STDOUT] New instance: 1407
21:37:35,281 INFO [STDOUT] New instance: 1408
21:37:35,296 INFO [STDOUT] New instance: 1409
21:37:35,343 INFO [STDOUT] New instance: 1410
21:37:35,359 INFO [STDOUT] New instance: 1411
21:37:35,406 INFO [STDOUT] New instance: 1412
21:37:35,421 INFO [STDOUT] New instance: 1413
21:37:35,468 INFO [STDOUT] New instance: 1414
21:37:35,468 ERROR [TimerServiceImpl] Cannot create txtimer
java.lang.IllegalStateException: Unable to persist timer
at org.jboss.ejb.txtimer.DatabasePersistencePolicy.insertTimer(DatabaseP
ersistencePolicy.java:138)
at sun.reflect.GeneratedMethodAccessor58.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatch
er.java:141)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:80)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:72)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.
java:245)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:644)
at org.jboss.mx.util.JMXInvocationHandler.invoke(JMXInvocationHandler.ja
va:273)
at $Proxy45.insertTimer(Unknown Source)
at org.jboss.ejb.txtimer.TimerServiceImpl.createTimer(TimerServiceImpl.j
ava:212)
at org.jboss.ejb.txtimer.TimerServiceImpl.createTimer(TimerServiceImpl.j
ava:178)
at org.jboss.tutorial.timer.bean.ExampleTimerBean.timeoutHandler(Example
TimerBean.java:41)
at sun.reflect.GeneratedMethodAccessor68.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:99)
at org.jboss.ejb3.AllowedOperationsInterceptor.invoke(AllowedOperationsI
nterceptor.java:32)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:66)
at org.jboss.aspects.tx.TxInterceptor$Required.invoke(TxInterceptor.java
:134)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInt
erceptor.java:61)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.ejb3.stateless.StatelessInstanceInterceptor.invoke(Stateles
sInstanceInterceptor.java:39)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.aspects.security.AuthenticationInterceptor.invoke(Authentic
ationInterceptor.java:63)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(Asynchrono
usInterceptor.java:91)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.ejb3.stateless.StatelessContainer.callTimeout(StatelessCont
ainer.java:96)
at org.jboss.ejb.txtimer.TimerImpl$TimerTaskImpl.run(TimerImpl.java:473)

at java.util.TimerThread.mainLoop(Unknown Source)
at java.util.TimerThread.run(Unknown Source)
Caused by: java.sql.SQLException: Unique constraint violation: in statement [in
sert into TIMERS (TIMERID,TARGETID,INITIALDATE,TIMERINTERVAL,INSTANCEPK,INFO) va
lues (?,?,?,?,?,?)]
at org.hsqldb.jdbc.Util.throwError(Unknown Source)
at org.hsqldb.jdbc.jdbcPreparedStatement.executeUpdate(Unknown Source)
at org.jboss.resource.adapter.jdbc.WrappedPreparedStatement.executeUpdat
e(WrappedPreparedStatement.java:227)
at org.jboss.ejb.txtimer.GeneralPurposeDatabasePersistencePlugin.insertT
imer(GeneralPurposeDatabasePersistencePlugin.java:156)
at org.jboss.ejb.txtimer.DatabasePersistencePolicy.insertTimer(DatabaseP
ersistencePolicy.java:134)
... 34 more
21:37:35,484 INFO [STDOUT] New instance: 1415
21:37:35,484 ERROR [TimerServiceImpl] Cannot create txtimer
java.lang.IllegalStateException: Unable to persist timer
at org.jboss.ejb.txtimer.DatabasePersistencePolicy.insertTimer(DatabaseP
ersistencePolicy.java:138)
at sun.reflect.GeneratedMethodAccessor58.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatch
er.java:141)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:80)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:72)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.
java:245)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:644)
at org.jboss.mx.util.JMXInvocationHandler.invoke(JMXInvocationHandler.ja
va:273)
at $Proxy45.insertTimer(Unknown Source)
at org.jboss.ejb.txtimer.TimerServiceImpl.createTimer(TimerServiceImpl.j
ava:212)
at org.jboss.ejb.txtimer.TimerServiceImpl.createTimer(TimerServiceImpl.j
ava:178)
at org.jboss.tutorial.timer.bean.ExampleTimerBean.timeoutHandler(Example
TimerBean.java:41)
at sun.reflect.GeneratedMethodAccessor68.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:99)
at org.jboss.ejb3.AllowedOperationsInterceptor.invoke(AllowedOperationsI
nterceptor.java:32)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:66)
at org.jboss.aspects.tx.TxInterceptor$Required.invoke(TxInterceptor.java
:134)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInt
erceptor.java:61)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.ejb3.stateless.StatelessInstanceInterceptor.invoke(Stateles
sInstanceInterceptor.java:39)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.aspects.security.AuthenticationInterceptor.invoke(Authentic
ationInterceptor.java:63)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(Asynchrono
usInterceptor.java:91)
at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.
java:88)
at org.jboss.ejb3.stateless.StatelessContainer.callTimeout(StatelessCont
ainer.java:96)
at org.jboss.ejb.txtimer.TimerImpl$TimerTaskImpl.run(TimerImpl.java:473)

at java.util.TimerThread.mainLoop(Unknown Source)
at java.util.TimerThread.run(Unknown Source)
Caused by: java.sql.SQLException: Unique constraint violation: in statement [in
sert into TIMERS (TIMERID,TARGETID,INITIALDATE,TIMERINTERVAL,INSTANCEPK,INFO) va
lues (?,?,?,?,?,?)]
at org.hsqldb.jdbc.Util.throwError(Unknown Source)
at org.hsqldb.jdbc.jdbcPreparedStatement.executeUpdate(Unknown Source)
at org.jboss.resource.adapter.jdbc.WrappedPreparedStatement.executeUpdat
e(WrappedPreparedStatement.java:227)
at org.jboss.ejb.txtimer.GeneralPurposeDatabasePersistencePlugin.insertT
imer(GeneralPurposeDatabasePersistencePlugin.java:156)
at org.jboss.ejb.txtimer.DatabasePersistencePolicy.insertTimer(DatabaseP
ersistencePolicy.java:134)
... 34 more

[bill.burke]

1) No business code should be relying on getting back the same instance of a stateless bean, including timers.

2) Given that, you may have uncovered a bug, our EJB3 implementation uses a ThreadLocal for its pooling so unless the EJB timer implementation is creating a new thread every time, then there is a bug. I have created a jira case for this:

http://jira.jboss.com/jira/browse/EJBTHREE-274

[bdecoste]

I've created a test using this bean code, but have been unable to recreate this exception. There is a new thread for every ejb timer, so that's not a problem.

[wauwau0977]

hi

i had exactly the same problem with my own implementation. i'm using the jboss 4.0.4.CR2 version and recreate the timer in my timeout action.

unfortunately i have somehow the problem to reproduce the behaviour. it occurs by hazard!

granby: did you figured out something?

Patrick Heusser

--
Patrick Heusser
http://www.x8ing.com/fractal

[germm]

Hi,

The problem is that the Timer ID generator may generate dupplicate Timer ID's after a server crash: http://jira.jboss.com/jira/browse/JBAS-3379

Regards,
Matthias

[mkleiderman]

The issue listed at: http://jira.jboss.com/jira/browse/JBAS-3379 says there's a workaround, but I can't fnd any details on what to do - could I get a pointer to how to implement the workaround?

Thanks,

- Matt

[konstantin.ermakov]

Hi!

in the $JBOSS_HOME/server/default/data/hypersonic/localdb.script after the server crash you will be able to find the following code:

INSERT INTO TIMERS ....

just delete this line and the code works fine then.

[galaxoid]

@Resource
private SessionContext ctx;
@Resource(mappedName="java:/DefaultDS")
private DataSource defaultDs;

public void createTimer() throws CustomException {
try {
Connection conn = defaultDs.getConnection();
Statement stmt = conn.createStatement();
stmt.execute("delete from TIMERS");
TimerService timerService = ctx.getTimerService();
timerService.createTimer(20000, 300000, "I'm a chinese, english is not good.");
} catch (Throwable ex) {
LogHome.getLog().error("", ex);
throw new CustomException(ex);
}
}

[mkleiderman]

This one has managed to bite me a couple of times, and I'm contemplating putting together an MBean to check all the timers on system startup and cancel any timers that look like zombies.

I'm having trouble making sense of the EJBTImerService MBeans getTimerService interface - it's looking for an ObjectName parameter, and I'm not certain what's the right parameter to pass in.

Is the text ObjectName the bit that follows target= in the listTimers return value? It looks like:
jboss.j2ee:service=EJB3,ear=[ear-name]ear,jar=[ejb-jar-name],name=[target-ejb-name]

Thanks,

- Matt