Hi Stephan,
I followed your advices, and it seems that I don't have the error when I inject
a UnitOfWork instead of a Provider<UnitOfWork>.
As far as I understand it, if a MyRunnable gets executed by the ExecutorService
before the end of the MyServletWorker, then it receives a copy of the existing
UnitOfWork instead of a new instance.
Is it a bug or did I misunderstand something ? I relied on a
Provider<UnitOfWork> because I wanted the UnitOfWork to be created when the
Runnable is executed rather than when the Runnable is instantiated.
Thank you for your answers, it has saved me *a lot* of debugging time.
// A time consuming job.
class MyRunnable implements Runnable {
@Inject Provider<EntityManager> entityManagerProvider;
@Inject UnitOfWork unitOfWork;
@Override
public void run()
{
try {
unitOfWork.begin();
EntityManager em = entityManagerProvider.get();
this.doTimeConsumingStuff(em);
} finally {
unitOfWork.end();
}
}
@Transactional
public void doTimeConsumingStuff(EntityManager em) {/* ... */}
}
Le 13 mai 2015 à 14:51:35, Stephan Classen ([email protected]) a écrit:
The persist framework takes care that every thread has its own entity manager.
So you don't need to do this.
Calling unitOfWork.end() will close the entity manager for you. So also no need
to do this manually.
The unitOfWork is a singleton. So you can inject it directly and don't need to
use the provider.
You must use the provider for the entityManager as you do.
Also important:
@Transactional works using interception at runtime. Threrefore it can only be
used on non private, non final and non static methods. Because for private,
final, or static methods the code can be inlined by the compiler. Then it is no
longer possible to intercept the method call at runtime.
Am 13. Mai 2015 14:35:39 MESZ, schrieb "JB Lézoray"
<[email protected]>:
Hi Laszio,
Thank you for your answer.
I think you pinpointed the problem, and I'm a step forward in resolving it.
Here is the MyRunnable implementation, it already relies on two providers for
EntityManager and UnitOfWork.
But now my question is : how to make sure that the Provider<EntityManager> in
the MyRunnable worker returns another EntityManager than the one in the
MyServletWorker ?
// A time consuming job.
class MyRunnable implements Runnable {
@Inject Provider<EntityManager> entityManagerProvider;
@Inject Provider<UnitOfWork> unitOfWorkProvider;
@Override
public void run()
{
UnitOfWork unitOfWork = null;
EntityManager em = null;
try {
unitOfWork = unitOfWorkProvider.get();
unitOfWork.begin();
em = entityManagerProvider.get();
this.doTimeConsumingStuff(em);
} finally {
if (unitOfWork != null) unitOfWork.end();
if (em != null && em.isOpen()) em.close(); // should it be explicitly
closed ?
}
}
@Transactional
private void doTimeConsumingStuff(EntityManager em) {/* ... */}
}
// Executed within the http worker thread.
// It Creates and submits the jobs.
class MyServletWorker {
@Inject Provider<EntityManager> entityManagerProvider;
@Inject ExecutorService executorService;
public void createAndSubmitJobs(MyData data) {
EntityManager em = entityManagerProvider.get();
Set<MyRunnable> jobs = createJobs(em, data);
for (MyRunnable job : jobs)
executorService.submit(job);
// ....
}
@Transactional
public Set<MyRunnable> createJobs(EntityManager em, MyData data) {/* ... */}
}
Le 13 mai 2015 à 13:16:59, Laszlo Ferenczi ([email protected]) a écrit:
Hi,
I think the issue will be in the MyRunnable class.
You create the MyRunnable instance in the http worker thread, if you simply
inject an EntityManager there it'll be the one bound to the current thread (the
http worker). After submitting it to a different thread you essentially leak
the transaction which can have many side effects (like when the same http
worker is selected again, the PersistFilter will try to start a new transaction
but it's already open for that thread - held by the long running background
job).
The correct way to handle this is to inject a Provider<EntityManager> in
MyRunnable and annotate the database using methods with @Transactional.
--
L
--
L
On Wed, May 13, 2015 at 11:58 AM, jbl <[email protected]> wrote:
Hello,
I'm relatively new to guice, and I've got a problem that I quite don't
understand.
I have a webapp based on guice, eclipse link, mysql that runs on a tomcat 7.
The app uses a com.google.inject.persist.jpa.JpaPersistModule and a
com.google.inject.persist.PersistFilter
For some requests the webapp creates a set of java.lang.Runnable, passes them
to a java.util.concurrent.ExecutorService, and returns. The runnables are
numerous time-consuming jobs that must be executed in background to avoid
blocking the request. Also, each job has to access the EntityManager. However,
the current implementation is quite naive:
@Inject private Provider<MyRunnable> myRunnableProvider;
@Inject private ExecutorService executorService;
MyRunnable runnable = myRunnableProvider.get();
executorService.submit(runnable);
This code runs fine on my development computer, but I get this exception when I
run it in a production environment :
java.lang.IllegalStateException: Work already begun on this thread. Looks like
you have called UnitOfWork.begin() twice without a balancing call to end() in
between.
at com.google.common.base.Preconditions.checkState(Preconditions.java:150)
~[guava-15.0.jar:na]
at
com.google.inject.persist.jpa.JpaPersistService.begin(JpaPersistService.java:73)
~[guice-persist-4.0.jar:na]
at com.jbl.MyRunnable.run(MyRunnable.java:107)
I think that this has something to do with the Scope, but I don't quite
understand how to correct this.
Thank you for any insight on this !
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[email protected]
Bâtiment Nucléole - 85 rue de Saint-Brieuc - 35 000 RENNES
Retrouvez-nous sur www.dolmen.bzh
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