Write to database asynchronously using Panache

[Brand Bintley]

I am facing the same situation described here:

https://stackoverflow.com/questions/62336094/quarkus-asynchronous

Essentially, I have a service into which ManagedExecutor is injected. The executor's task then reads from the database using panache, then alters the entity and writes it back to the database.

Upon writing, the following exception is thrown:

javax.persistence.TransactionRequiredException: Transaction is not active, consider adding @Transactional to your method to automatically activate one.

The weird part is that the run() method of the task is indeed annotated with @Transactional.

Any idea how to address this?

[Brand Bintley]

Please help. Below is my reproducer code. Obviously, if I replace executor.execute(task); with  task.run(); things work well because the execution becomes synchronous. I am trying to see how to persist entities asynchronously while using Panache. 

@Path("/hello")

public class GreetingResource {

@Inject ManagedExecutor executor;

@GET

@Produces(MediaType.TEXT_PLAIN)

@Transactional

public String hello() {

PersonTask task= new PersonTask();

    executor.execute(task);

        return "hello";

}

}

@Entity

public class Person extends PanacheEntity {

       public String name=UUID.randomUUID().toString();

}

public class PersonTask implements Runnable{

@Transactional

public void run() {

Person p = new Person();

 p.persistAndFlush();

}

}

The error is:

ARJUNA012094: Commit of action id 0:ffffc0a8010e:e950:60200089:0 invoked while multiple threads active within it.

ARJUNA012107: CheckedAction::check - atomic action 0:ffffc0a8010e:e950:60200089:0 commiting with 2 threads active!

Thread Thread[executor-thread-2,5,executor] threw an uncaught exception: javax.persistence.TransactionRequiredException: Transaction is not active, consider adding @Transactional to your method to automatically activate one.

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[Paul Carter-Brown]

Try annotating the run() with @Transactional(REQUIRES_NEW)

To view this discussion on the web visit https://groups.google.com/d/msgid/quarkus-dev/CABEjM6Qsv%2B0y0QzpwbD2cKb7t%3Dp8gdzwgywzpcR76eUcrjgHjg%40mail.gmail.com.

[Brand Bintley]

Thanks. REQUIRES_NEW as well as MANDATORY didn't help. This is what works for me.

@Path("/hello")

public class GreetingResource {

@Inject ManagedExecutor executor;

@Inject TransactionManager tm; 

@GET

@Produces(MediaType.TEXT_PLAIN)

public String hello() {

PersonTask task= new PersonTask();

task.setTm(tm);

    executor.execute(task);

        return "hello";

}

}

public class PersonTask implements Runnable{

       protected TransactionManager tm; 

public void setTm(TransactionManager tm) {

this.tm = tm;

}

@Override

public void run() {

try {

   tm.begin();

   Person p = new Person();

   p.persistAndFlush();

   tm.commit();

}catch(Exception e) {

e.printStackTrace();

}

}

}

[Stephane Epardaud]

Hi,

So what happens here is that you're opening a transaction, then starting an async task with the same transaction, then before it's done you return a response to the client and we close the transaction because your method is done.

What you should do if you want to make it async, but not reply to the user until the transaction is finished is this:

@Path("/hello")

public class GreetingResource {

 @Inject ManagedExecutor executor;

 @GET

 @Produces(MediaType.TEXT_PLAIN)

 @Transactional

 public CompletionStage<String> hello() {

PersonTask task= new PersonTask();

     return executor.runAsync(task).thenApply(v -> "hello");

 }

}

@Entity

public class Person extends PanacheEntity {

       public String name=UUID.randomUUID().toString();

}

public class PersonTask implements Runnable{

public void run() {

 Person p = new Person();

 p.persistAndFlush();

}

}

At least this way, you're sure the task is done before you return your response to the user, and we won't close the transaction before you're done.

To view this discussion on the web visit https://groups.google.com/d/msgid/quarkus-dev/CABEjM6Qsv%2B0y0QzpwbD2cKb7t%3Dp8gdzwgywzpcR76eUcrjgHjg%40mail.gmail.com.

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Stéphane Épardaud

[Brand Bintley]

Hi Stephane,

Thanks for your input. What I really want is to respond to the user and then continue the processing asynchronously. That's why I think the transaction is needed for the execution of the run() method. What seems to happen is that the @Transactional annotation is ignored when the run method is executed by the executors.

I hope that makes sense.

Brand

[Stephane Epardaud]

OK, yes the @Transactional annotation is only used on beans, and your Runnable function is not a bean.

You will need something like this:

@Path("/hello")

public class GreetingResource {

         @Inject Service service;

 @Inject ManagedExecutor executor;

 @GET

 @Produces(MediaType.TEXT_PLAIN)

 public String hello() {

PersonTask task= new PersonTask();

     executor.execute(() -> service.run());

                return "hello";

 }

}

@Entity

public class Person extends PanacheEntity {

       public String name=UUID.randomUUID().toString();

}

@ApplicationScoped

public class Service {

        @Transactional

--

Stéphane Épardaud