I have a working Multi-Master Replication setup with two masters (Fedora
Directory Server 1.0.4). The setup works fine as long as I do not update the
same object via both Masters. When the later happens (application driven), one
of the Master crashes. This server does not generate a core dump.

I included the logs in the user mailing list and Richard had the following comment:

"Thanks.  This is a very interesting test.  You are generating replication
conflicts:
[05/Sep/2007:13:15:40 -0400] conn=51 op=29 csn=46dee55f000200030000 - Naming
conflict ADD. Renamed existing entry to
nsuniqueid=99277847-1dd111b2-80dfcd7f-b7bc0000+ou=repltest

It looks as though you are repeatedly adding and deleting the same entry from
both servers at the same time, which should be fine.  Could you post your script
that you use to generate these entries? "

I send the important pieces of my java class:

"Richard, this is a java class, using jndi.

The relevant methods are:
1. 
public InitialDirContext connect(String host, int port) throws NamingException
   {
       InitialDirContext context = null;
       Hashtable environment = new Hashtable();
       environment.put( Context.INITIAL_CONTEXT_FACTORY,
"com.sun.jndi.ldap.LdapCtxFactory" ); 
       environment.put( "java.naming.ldap.version", "3" ); 
       environment.put(Context.SECURITY_PRINCIPAL, "cn=Directory Manager");
       environment.put(Context.SECURITY_CREDENTIALS, "xxxxxx");
       environment.put(Context.SECURITY_AUTHENTICATION, "simple");
       
       // timeouts
       environment.put( "com.sun.jndi.dns.timeout.initial", "2000" ); 
       environment.put( "com.sun.jndi.dns.timeout.retries", "3" ); 

       environment.put( Context.PROVIDER_URL, "ldap://" + host + ":" +
port+"/o=test" );

       context = new InitialDirContext( environment);
       System.out.println("Connected to " + host);
                
       return context;
       
   }

2.
public void addEntry(InitialDirContext ctx) {
      
      // Create attributes to be associated with the new context
         Attributes attrs = new BasicAttributes(true); // case-ignore
         Attribute objclass = new BasicAttribute("objectclass");
         objclass.add("top");
         objclass.add("organizationalUnit");
         attrs.put(objclass);
      
         // Create the context
         Context result;
         try {
            result = ctx.createSubcontext("ou=test", attrs);
         
            result.close();
         } catch (NameAlreadyBoundException e) {
            // ignore
            // just logg it .......
         } catch (NamingException e) {
            e.printStackTrace();
            this.destroy();
         }
      }

3.
public void deleteEntry(InitialDirContext ctx) { 

         try {
            ctx.destroySubcontext("ou=test");
            //ctx.close();
         } catch (NameNotFoundException e) {
            // ignore
           // just logg it .......
            }
         } catch (NamingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            this.destroy();
         }
      }

4. Start of the thread:
public void start() {
          int counter = 0;
          
          for (int i = start; i < stop; i++) {
              try {
                 addEntry(ctx);
                 //....some kind of logging
                 this.sleep(100);
                 deleteEntry(ctx);
                 //....some kind of logging
                 this.sleep(50);
              } catch (Exception e) {
                 e.printStackTrace();
              }
              
          }
          //close context;
          try {
            ctx.close();
         } catch (NamingException e) {
            e.printStackTrace();
         }
      }     

Then, I just call this thread for my two masters (MasterOne and MasterTwo).

Of course, when I pause for a longer time between the add and delete, it takes
longer that it happens."