7 Replies Latest reply on Feb 2, 2011 1:21 PM by piotrekde

    Number of SLSB in pool in case of asynchronous calls

    piotrekde
    piotrekde Jan 31, 2011 2:49 PM

      Hello,

       

      I occurred weird situation using JBoss 5 and EJB 3.0. Please take a look at the source code below - it is simplified example but I think that clearly reflecting this issue.

       

      ComputerBean dispatches work to pooled ProcessorBeans using AsyncUtils. I noticed that number of created SLSB never goes down (I see it printing shared COUNTER variable). So I decided to set maximum pool size explicitly and observe what will happen.

       

       

      ComputerRemote (remote interface of SFSB dispatching work)

      import javax.ejb.Remote;


@Remote
public interface ComputerRemote {
    void startComputations();
}

       

       

      ProcessorLocal (local interface of SLSB doing computations (dispatched previously by ComputerRemote/ComputerBean))

      import javax.ejb.Local;


@Local
public interface ProcessorLocal {
    void compute(int i);
}

       

      And implementations:

       

      ComputerBean (dispatching work using JBoss AsyncUtils - ComputerBean do not waits for ProcessorLocal until it will finish computations)

      @Stateful
public class ComputerBean implements ComputerRemote {


    @EJB
    private ProcessorLocal processor;


    public void startComputations() {
        Random r = new Random();


        while(true) {
            AsyncUtils.mixinAsync(processor).compute(r.nextInt());
        }
    }
}

       

       

      And ProcessorBean using fixed pool size:

       

      
@Stateless
@PoolClass (value=org.jboss.ejb3.StrictMaxPool.class, maxSize=5, timeout=10000)
public class ProcessorBean implements ProcessorLocal {

    private static AtomicInteger COUNTER = new AtomicInteger(0);

    @PostConstruct
    public void init() {
        System.out.println("constructing nr: " + COUNTER);
        COUNTER.incrementAndGet();
    }

    @PreDestroy
    public void destroy() {
        System.out.println("destroying nr:" + COUNTER);
        COUNTER.decrementAndGet();
    }

    public void compute(int i) {
        System.out.println("----------------> " + COUNTER);


        // some dummy computations - it's here only in order to take some time
        double d = 0.3;
        for (int j=0; j<100; j++) {
            d+= 0.2 % 4 + i;
        }
    }
}

       

       

      I would expect that on console COUNTER will be printed with maximum value = 5.

       

      But reality is:

       

      20:25:10,979 INFO  [STDOUT] constructing nr: 0

      20:25:11,008 INFO  [STDOUT] constructing nr: 1

      20:25:11,067 INFO  [STDOUT] constructing nr: 2

      20:25:11,096 INFO  [STDOUT] constructing nr: 3

      20:25:11,118 INFO  [STDOUT] constructing nr: 4

      20:25:11,134 INFO  [STDOUT] constructing nr: 5

      20:25:11,158 INFO  [STDOUT] constructing nr: 6

      20:25:11,185 INFO  [STDOUT] constructing nr: 7

      20:25:11,211 INFO  [STDOUT] constructing nr: 8

      (...)

      20:25:11,467 INFO  [STDOUT] constructing nr: 15

      20:25:11,522 INFO  [STDOUT] ----------------> 16

      20:25:11,524 INFO  [STDOUT] ----------------> 16

      20:25:11,524 INFO  [STDOUT] ----------------> 16

      20:25:11,525 INFO  [STDOUT] ----------------> 16

      20:25:11,526 INFO  [STDOUT] ----------------> 16

      20:25:11,527 INFO  [STDOUT] ----------------> 16

      (...)

       

      up to even 26!

       

      My question is obvious: what is going on? I expect to have maximum 5 SLSB instances...

       

      I have to use EJB3.0 and JBoss5 - at this moment I cannot switch versions.

       

      Thank you in advance for all hints,

      Piotr