NotSerializableException MemoryUser?

Hi,

I'm running Tomcat 6.0.20 in a cluster on 3 nodes. If I restart one I get this exception:


Caused by: java.io.NotSerializableException: org.apache.catalina.users.MemoryUser
   at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1156)
   at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
   at java.util.LinkedList.writeObject(LinkedList.java:943)
   at sun.reflect.GeneratedMethodAccessor127.invoke(Unknown Source)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
   at java.lang.reflect.Method.invoke(Method.java:597)
   at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
   at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1461)
   at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
<Server port="8005" shutdown="SHUTDOWN">

 <GlobalNamingResources>
   <!-- Used by Manager webapp -->
   <Resource name="UserDatabase" auth="Container"
             type="org.apache.catalina.UserDatabase"
      description="User database that can be updated and saved"
          factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
         pathname="conf/tomcat-users.xml" />
 </GlobalNamingResources>

 <Service name="Catalina">
   <Connector port="8080" maxHttpHeaderSize="8192"
              maxThreads="300" minSpareThreads="25" maxSpareThreads="75"
              enableLookups="false" redirectPort="8443" acceptCount="1024"
              connectionTimeout="20000" disableUploadTimeout="true"
              compression="on"
              compressableMimeTypes="text/html,text/xml,text/plain,text/javascript,text/css"/>

   <Connector port="8443" debug="0" scheme="https" secure="true" SSLEnabled="true"
              clientAuth="false" sslProtocol="TLS"
              keystoreFile="/etc/tomcat6/STAR_example.com.p12"
              keystoreType="PKCS12"
              keystorePass="*****" />

   <Engine name="Catalina" defaultHost="www.example.com">
     <Realm className="org.apache.catalina.realm.UserDatabaseRealm"
            resourceName="UserDatabase" />
               <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster">
                       <Channel className="org.apache.catalina.tribes.group.GroupChannel">
                               <Membership className="org.apache.catalina.tribes.membership.McastService" port="45525" />
                       </Channel>
               </Cluster>

       <!-- Zorg dat de appBase regel direct na de 'Host name' regel staat -->
       <Host name="www.example.com"
               appBase="/data/webapps/crm-VERSIE_2_5/deployed"
               unpackWARs="true" autoDeploy="false" reloadable="false"
               usePooling="false"
               xmlValidation="false" xmlNamespaceAware="true">
       <Alias>www2.example.com</Alias>
       </Host>
   </Engine>

 </Service>
</Server>

What can I do to make the MemoryUser  serializable and why is it trying to sync it with other nodes?

Ronald.