Many MySQL connections

Question

I'm a bit lost about this fact:

show status like 'con%';

+-----------------------------------+-------+
| Variable_name                     | Value |
+-----------------------------------+-------+
| Connection_errors_accept          | 0     |
| Connection_errors_internal        | 0     |
| Connection_errors_max_connections | 0     |
| Connection_errors_peer_address    | 0     |
| Connection_errors_select          | 0     |
| Connection_errors_tcpwrap         | 0     |
| Connections                       | 10535 |
+-----------------------------------+-------+

I read some similar question here, but the problems in those cases where not mine, so here I am.

I use MySQL and Hibernate. In my webapp there is this static HibernateUtil class to access the database:

import org.apache.log4j.Logger;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

    private static final Logger log = Logger.getLogger(HibernateUtil.class);        
    private static SessionFactory sessionFactory;    

    static {

        try {
            sessionFactory = new Configuration().configure("hibernate.cfg.xml").buildSessionFactory();
        } catch (Throwable ex) {
            // error handling
        }
    }

  public static final ThreadLocal session = new ThreadLocal();

  public static Session currentSession() throws HibernateException {

        Session s = null;
        try {
            s = (Session) session.get();
        } catch(Exception e) {
            // error handling
        }

        // Open a new Session, if this thread has none yet
        if (s == null) {
            try {
                s = sessionFactory.openSession();
            } catch(Exception e) {
                // error handling
            }

            try {
                s.getTransaction();
            } catch(Exception e){
                // error handling
            }
            Transaction tx = null;

            while(tx==null){
                try {
                    tx = s.beginTransaction();
                    // Store it in the ThreadLocal variable
                } catch(Exception j) {
                    // error handling
                }
            }
            session.set(s);        
        }
        return s;
    }


public static void closeSession() throws HibernateException {
    Session s = (Session) session.get();
    if (s != null){
        try {
            s.getTransaction().commit();
            s.close();
        } catch(Exception e) {
            // error handling
        }
    }
    session.set(null);
  }

 public static void errorSession() throws HibernateException {
    Session s = (Session) session.get();
        try {
            s.getTransaction().rollback();
            s.close();
        } catch(Exception e) {
            // error handling
        }
    session.set(null);
  }

}

Then I call the util class like in this example:

private MyTable getMyTable() {
    try {
        Session session = currentSession();
        // some prepared statement
        return myTable;
    } catch (HibernateException e) {
        errorSession();
        return null;
    } finally {
        closeSession();
    }
}

So basically I close the connection on success (closeSession) and on error (errorSession). Now why do I see so many connections in the MySQL console?

Answer 1

The meaning of connections is not what you think. As said in docs connections means:

The number of connection attempts (successful or not) to the MySQL server.

So you do not have 10535 active connections as you think.

Answer 2

To see the actual connect threads use:

SHOW STATUS LIKE 'Threads_connected';