Hibernate in load-balanced scenarios... caching problems?

emsuarez · **Posted:** Fri Apr 16, 2004 2:03 pm

Hi

I am having a strange problem in Hibernate.
I have a web app that is running in a load-balancing environment. So there are two physical servers responding to web requests.
In the application, there is an action that updates a record, the hibernate code is doing:

Code:

            session.save(loan);
            session.flush();
            session.connection().commit();

then there is another action that retrieves the list of objects:

Code:

allLoans = session.find("from Loan as Loan where status='a'");

but sometimes (due to the load balancing I guess), the application shows the previous version of the data, before the update, that is probably returning cached data, because if I refresh the page, it shows the correct updated information, when the request goes to the other server, and the session.find loads fresh data.

So this looks to me like somehow the data is being cached by one server, because in reality there are two hibernate session running... one on each server.

Is there a way to force Hibernate to return fresh data in a "session.find()" ?

I even added a "session.flush()" before doing the "session.find()" but that didn't help.

Is there some other thing that I am missing here?

Thanks,

christian · **Posted:** Fri Apr 16, 2004 2:07 pm

If you have no second-level cache for those objects, there is no cache outside of the two Session scopes. You will see changes in one Session as soon as the other Session commits (also check your JDBC connection isolation level).

anthony · **Posted:** Fri Apr 16, 2004 2:08 pm

nop it's due to bad management of the hibernate session

take a look at threadlocal session
just search 'open session in view' in the site

anthony · **Posted:** Fri Apr 16, 2004 2:09 pm

oh excuse me christian, we have replied at the same time, my 'nop' was for emsuarez of course...

emsuarez · **Posted:** Fri Apr 16, 2004 2:17 pm

Well, actually I am using the ThreadLocalSession and this code gets called after the object (Loan) has been updated.

Code:

    public static void closeHibernateSession() {
        Session session = (Session) threadLocalSession.get();
        AppLog.info("BaseDAO: closing session: " + session);
        threadLocalSession.set(null);
        try {
            if (session != null) session.close();
        } catch (HibernateException e) {
            AppLog.error("Couldn't close the hibernate session" + e);
            e.printStackTrace();
        }
    }

anthony · **Posted:** Fri Apr 16, 2004 2:20 pm

i had exactly the same bug at the beginning i used hibernate (one year ago) and the reason was the management of the session.

You should consider using the servlet filter to ensure that a new sesison is used for each request

emsuarez · **Posted:** Fri Apr 16, 2004 2:33 pm

Thanks delpouve for your help.

could this also be related that I refactored and now I am instantiating the SessionFactory in a Singleton? So each server has one SessionFactory which returns different sessions to each invocation.

I did review the Open Session in View http://www.hibernate.org/43.html

But this pattern is also creating a SessionFactory and keeping it in the Servlet's context, which works the same as a Singleton in this case.

Or should I create a SessionFactory for each request?

Thanks,

anthony · **Posted:** Fri Apr 16, 2004 2:43 pm

you only need one sessionFactory per server