GWT-Hibernate application do not release session resources

We have developed a gwt-hibernate multi database application which is running on Glassfish and using Oracle datatabase. After a connection to a default database which is addressed by a default persistence unit like the following:

<persistence-unit name="DefaultDBConnection" transaction-type="RESOURCE_LOCAL">

<provider>org.hibernate.ejb.HibernatePersistence</provider>

<properties>

<property name="hibernate.dialect" value="org.hibernate.dialect.Oracle8iDialect" />

<property name="hibernate.connection.driver_class" value="oracle.jdbc.driver.OracleDriver" />

<property name="hibernate.connection.username" value="user" />

<property name="hibernate.connection.password" value="******************" />

<!-- <property name="hibernate.hbm2ddl.auto" value="update" /> -->

<property name="hibernate.connection.url" value="jdbc:oracle:thin:@server:1521:orcl" />

<property name="hibernate.show_sql" value="true" />

<!-- <property name="hibernate.format_sql" value="true"/> -->

<property name="hibernate.max_fetch_depth" value="3" />

<property name="hibernate.cache.provider_class" value="org.hibernate.cache.NoCacheProvider" />

<property name="hibernate.query.plan_cache_max_strong_references" value="8" />

<property name="hibernate.query.plan_cache_max_soft_references" value="16" />

<property name="connection.provider_class" value="org.hibernate.connection.C3P0ConnectionProvider" /> 

<property name="hibernate.c3p0.min_size" value="5" />

<property name="hibernate.c3p0.max_size" value="200" />

<property name="hibernate.c3p0.timeout" value="300" />

<property name="hibernate.c3p0.max_statements" value="50" />

<property name="hibernate.c3p0.idle_test_period" value="3000" />

<property name="hibernate.generate_statistics" value="true" />

</properties>

</persistence-unit>

the database selection is done by the user login through our HibernateGwt class which connects to the proper database through a different persistence unit.

The EntityManager to interact with the proper database is then opened-taken by the following instructions in the gwt RemoteServiceServlet:

  EntityManager session = getSession();

where 

private javax.persistence.EntityManager getSession() {

return HibernateGwt.getInstance().getEntityManager(this);

}

and "this" is a com.google.gwt.user.server.rpc.RemoteServiceServlet, while 

        private static HibernateGwt singleton = new HibernateGwt();

private HashMap<String,javax.persistence.EntityManagerFactory> factoryCollection = new HashMap<String,javax.persistence.EntityManagerFactory>();

private ThreadLocalUtil entityManagerCollection = new ThreadLocalUtil(); 

public javax.persistence.EntityManager getEntityManager(Object service) {

ThreadLocal myTdl;

javax.persistence.EntityManager entityManager;

                //to get the right persistence name from the user logged in which is stored as a session variable

String persistenceUnit = getPersistenceUnit(service); 

entityManager = (EntityManager) entityManagerCollection.getThreadVariable(persistenceUnit);

if (entityManager == null || !entityManager.isOpen()) {

entityManager = getFactory(persistenceUnit).createEntityManager();

entityManagerCollection.setThreadVariable(persistenceUnit, entityManager);

}

return entityManager;

}

At user logout we close the connection as follow:

          HibernateGwt.getInstance().close(null);

where 

public void close(String persistenceUnit) {

if (persistenceUnit == null)

persistenceUnit = getPersistenceUnit();

closeEntityManager(persistenceUnit);

if (factoryCollection.containsKey(persistenceUnit)){

javax.persistence.EntityManagerFactory factory = factoryCollection.get(persistenceUnit);

if (factory != null) {

factory.close();

factory = null;

}

factoryCollection.remove(persistenceUnit);

}

}

and

public void closeEntityManager(String persistenceUnit) {

javax.persistence.EntityManager entityManager;

if (persistenceUnit == null)

persistenceUnit = getPersistenceUnit();

entityManager = (EntityManager) entityManagerCollection.getThreadVariable(persistenceUnit);

if (entityManager != null && entityManager.isOpen()) {

entityManager.close();

}

entityManagerCollection.setThreadVariable(persistenceUnit, null);

}

Please, can someone help us understand what we are doing wrong to not let Glassfish release resources and fall into a degrade of performace until we restart it?

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