Hi

I have 2 Jboss3.2.5 applications servers working in a cluster.
I'm using for primary key generation The pattern "sequence blocks" taken from the book ejb design patterns.
However when i have something like 5 threads that are trying to create new entities then i get DuplikateKeyException on the primary key. (with only 1 jboss server not in a cluster everything is fine).
I was wondering if anybody could help me pin out the problem, following is my code:

I estimated it might be an Isolation level problem, however i have updated the isolation level to be serializable in that way in mysql ds and the problem still happend...

<user-name>root</user-name>
 <password></password>
 <TransactionIsolation>TRANSACTION_SERIALIZABLE</TransactionIsolation>

package messaging_as.domain.util;

import javax.ejb.*;

import messaging_as.util.jmx.ConfigContainer;

abstract public class SequenceBean implements EntityBean {
 EntityContext entityContext;
 public java.lang.String ejbCreate(java.lang.String name) throws CreateException {
 setName(name);
 return null;
 }
 public void ejbPostCreate(java.lang.String name) throws CreateException {
 setSIndex(ConfigContainer.getJMXPropertiesFacade().getSequenceSessionBeanStartIndex());
 }

 public void ejbRemove() throws RemoveException {
 }

 public abstract void setName(java.lang.String name);
 public abstract void setSIndex(int sIndex);
 public abstract java.lang.String getName();
 public abstract int getSIndex();
 public void ejbLoad() {
 }

 public void ejbStore() {
 }

 public void ejbActivate() {
 }

 public void ejbPassivate() {
 }

 public void unsetEntityContext() {
 this.entityContext = null;
 }
 public void setEntityContext(EntityContext entityContext) {
 this.entityContext = entityContext;
 }
 public int getValueAfterIncrementingBy(int blockSize) {
 this.setSIndex(this.getSIndex()+ blockSize);
 return this.getSIndex();
 }
}

package messaging_as.domain.util;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.ejb.CreateException;
import javax.ejb.FinderException;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
import javax.naming.Context;
import javax.naming.NamingException;

import messaging_as.domain.AlbumElementHome;
import messaging_as.domain.AlbumElementShareHome;
import messaging_as.domain.UserHome;
import messaging_as.service.exceptions.InternalException;
import messaging_as.util.jmx.JMXPropertiesFacade;
import messaging_as.util.sql.MASConnectionManager;

import org.apache.log4j.Category;

public class SequenceSessionBean implements SessionBean {
 SessionContext sessionContext;
 private Category _log;
 private class Entry {
 Sequence sequence;
 int last;
 };

 private java.util.HashMap _entries = new java.util.HashMap();
 private int _blockSize;
 private int _retryCount;
 private SequenceHome _sequenceHome;

 public void ejbCreate() throws CreateException {
 _log = Category.getInstance(getClass());
 }

 public void ejbRemove() {

 }
 public void ejbActivate() {

 }
 public void ejbPassivate() {

 }

 public void setSessionContext(SessionContext sessionContext) {
 this.sessionContext = sessionContext;
 Context namingContext = null;
 try {
 namingContext = new javax.naming.InitialContext();
 _blockSize = JMXPropertiesFacade.getInstance().getSequenceSessionBeanBlockSize();
 _retryCount = JMXPropertiesFacade.getInstance().getSequenceSessionBeanRetryCount();

 _sequenceHome = (SequenceHome) namingContext.lookup("SequenceLocalHome");
 }
 catch (NamingException e) {
 _log.error(e.getMessage(), e);
 }
 }

 public void synch() throws InternalException {
 Connection connection = null;
 ResultSet resultSet = null;
 Statement statement = null;
 int maxObjectID = 0, maxUID = 0, maxShareID = 0;
 try {
 connection = MASConnectionManager.getInstance().createConnection();

 String sql = "select max(" + AlbumElementHome.FIELD_NAME_OBJECT_ID + ") maxObjectID from " + AlbumElementHome.TABLE_NAME;
 statement = connection.createStatement();
 _log.debug("SQL : " + sql);
 statement.execute(sql);
 resultSet = statement.getResultSet();
 if (resultSet.next()) {
 maxObjectID = resultSet.getInt("maxObjectID");
 _log.debug(String.valueOf(maxObjectID));
 }
 resultSet.close();
 statement.close();
 ((Sequence) _sequenceHome.findByPrimaryKey(AlbumElementHome.JNDI_NAME)).setSIndex(maxObjectID + 1);

 sql = "select max(" + UserHome.FIELD_UID + ") maxUID from " + UserHome.TABLE_NAME;
 statement = connection.createStatement();
 _log.debug("SQL : " + sql);
 statement.execute(sql);
 resultSet = statement.getResultSet();
 if (resultSet.next()) {
 maxUID = resultSet.getInt("maxUID");
 _log.debug(String.valueOf(maxUID));
 }
 resultSet.close();
 statement.close();
 ((Sequence) _sequenceHome.findByPrimaryKey(UserHome.JNDI_NAME)).setSIndex(maxUID + 1);

 sql = "select max(" + AlbumElementShareHome.FIELD_SHARE_ID + ") maxShareID from " + AlbumElementShareHome.TABLE_NAME;
 statement = connection.createStatement();
 _log.debug("SQL : " + sql);
 statement.execute(sql);
 resultSet = statement.getResultSet();
 if (resultSet.next()) {
 maxShareID = resultSet.getInt("maxShareID");
 _log.debug(String.valueOf(maxShareID));
 }
 resultSet.close();
 statement.close();
 ((Sequence) _sequenceHome.findByPrimaryKey(AlbumElementShareHome.JNDI_NAME)).setSIndex(maxShareID + 1);

 } catch (SQLException e1) {
 _log.error(e1.getMessage(), e1);
 } catch (FinderException e) {
 throw new InternalException(e);
 } finally {
 try {
 if (connection != null && !connection.isClosed()) connection.close();
 } catch (SQLException e) {
 _log.error(e.getMessage(), e);
 }
 }

 }

 public int getNextSequenceNumber(String name) {
 try
 {
 Entry entry = (Entry) _entries.get(name);

 if (entry == null)
 {
 // add an entry to the sequence table
 entry = new Entry();
 try
 {
 entry.sequence = _sequenceHome.findByPrimaryKey(name);
 }
 catch (javax.ejb.FinderException e)
 {
 _log.info("can't find sequence: " + name + " trying to create it");
 // if we couldn't find it, then create it...
 entry.sequence = _sequenceHome.create(name);
 _log.info("sequence: " + name + " created");
 }
 _entries.put(name, entry);
 }
 if (entry.last % _blockSize == 0)
 {
 for (int retry = 0; true; retry++)
 {
 try
 {
 entry.last = entry.sequence.getValueAfterIncrementingBy(_blockSize);
 break;
 }
 catch (javax.ejb.TransactionRolledbackLocalException e)
 {
 if (retry < _retryCount)
 {
 // we hit a concurrency exception, so try again...
 _log.info("RETRYING");
 continue;
 }
 else
 {
 // we tried too many times, so fail...
 throw new javax.ejb.EJBException(e);
 }
 }
 }
 }

 return entry.last++;
 }
 catch (javax.ejb.CreateException e)
 {
 throw new javax.ejb.EJBException(e);
 }
}


}

 <container-transaction>
 <method>
 <description />
 <ejb-name>SequenceSession</ejb-name>
 <method-name>getNextSequenceNumber</method-name>
 <method-params>
 <method-param>java.lang.String</method-param>
 </method-params>
 </method>
 <trans-attribute>RequiresNew</trans-attribute>
 </container-transaction>

 <container-configurations>
 <container-configuration>
 <container-name>Standard CMP 2.x EntityBean with cache invalidation</container-name>
 <commit-option>A</commit-option>
 <cache-invalidation>True</cache-invalidation>
 </container-configuration>
 </container-configurations>
.
.
.
 <entity>
 <ejb-name>Sequence</ejb-name>
 <local-jndi-name>SequenceLocalHome</local-jndi-name>
 <!-- no cache for this entity bean -->
 </entity>