Tomcat's Clustering / Session Replication not replicating properly

Question 1

We had this identical issue. Although not documented anywhere, what solved it for me was to simply move the <Manager> tag from server.xml to the global context.xml (bringing it out of the <Server>...<Cluster>... group and into the <Context> group). As soon as we did this, everything "magically" began working. This only applied to Tomcat 7...Tomcat 6 worked perfectly with the setup you describe above (and as the documentation describes).

<Context>
    <Manager className="org.apache.catalina.ha.session.DeltaManager"
             expireSessionsOnShutdown="false"
             notifyListenersOnReplication="true" />
</Context>

Now just remove the <Manager> tag from your Cluster group in server.xml and you're done.

Question 2

on server.xml just add:

<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"
             channelSendOptions="6"/>

and, in your context.xml:

<Manager className="org.apache.catalina.ha.session.DeltaManager"
         expireSessionsOnShutdown="false"
         notifyListenersOnReplication="true" />

it worked for me, i'm using Tomcat 7 and Tomcat 8

Question 3

Our solution was to add the <distributable/> tag to the WEB-INF/web.xml file under the <web-app> element. Not sure why this worked for us an not for the OP.

By the way, Jason's solution worked for us too.

Question 4

If you want to enable Clustering for specific deployed application, you can using below example

server.xml

  <Host name="localhost"  appBase="webapps"
        unpackWARs="true" autoDeploy="true">

      <Channel className="org.apache.catalina.tribes.group.GroupChannel">
        <Membership className="org.apache.catalina.tribes.membership.McastService"
                    address="228.0.0.4"
                    port="45564"
                    frequency="500"
                    dropTime="3000"/>
        <Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver"
                  address="auto"
                  port="4000"
                  autoBind="100"
                  selectorTimeout="5000"
                  maxThreads="6"/>

        <Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter">
          <Transport className="org.apache.catalina.tribes.transport.nio.PooledParallelSender"/>
        </Sender>
        <Interceptor className="org.apache.catalina.tribes.group.interceptors.TcpFailureDetector"/>
        <Interceptor className="org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor"/>
      </Channel>

      <Valve className="org.apache.catalina.ha.tcp.ReplicationValve"
             filter=""/>
      <Valve className="org.apache.catalina.ha.session.JvmRouteBinderValve"/>

      <Deployer className="org.apache.catalina.ha.deploy.FarmWarDeployer"
                tempDir="/tmp/war-temp/"
                deployDir="/tmp/war-deploy/"
                watchDir="/tmp/war-listen/"
                watchEnabled="false"/>

      <ClusterListener className="org.apache.catalina.ha.session.JvmRouteSessionIDBinderListener"/>
      <ClusterListener className="org.apache.catalina.ha.session.ClusterSessionListener"/>

      <Manager className="org.apache.catalina.ha.session.DeltaManager"
       expireSessionsOnShutdown="false"
       notifyListenersOnReplication="true"/>

    <Resource auth="Container" driverClassName="oracle.jdbc.OracleDriver" factory="com.atomikos.tomcat.EnhancedTomcatAtomikosBeanFactory" minPoolSize="4" maxPoolSize="50" name="jdbc/myoracle/myconect" password="sdfhsfghsgfsfg" type="com.atomikos.jdbc.nonxa.AtomikosNonXADataSourceBean" uniqueResourceName="uniresource" url="jdbc:oracle:thin:@10.10.10.10.:1521:abc" user="user"/>
    </Context>

Question 5

According to Tomcat docs you need to do one of these two (NOT both):

Specify in web.xml <distributable/> to enable clustering and use the default <Manager> specified in the server.xml or...
Add a <Manager> at the application level inside context.xml

Question 6

None of the suggestions above worked. For those of you who are following the Ramki tutorial, the problem you're having is to have a full list in the first tomcat instance, but an empty list in the other instances. The only thing you have to do differently from the video tutorial is to change the scriptlet in the index.jsp to:

String bookName = request.getParameter("bookName");
List<String> listOfBooks = (ArrayList<String>) request.getSession().getAttribute("Books");
if(listOfBooks == null) {
    listOfBooks = new ArrayList<String>();                                      
}
if(bookName != null) {
    listOfBooks.add(bookName);
}
request.getSession().setAttribute("Books", listOfBooks);
for(String book: listOfBooks) {
    out.println("<li>" + book + "</li><br />");
}

What this means is to not set the Books attribute just when listOfBooks is empty, but every time. That'll notify all the running tomcat instances that the list CONTENTS have been changed, they'll rescan the list, and show the full list in all instances, not just on the running one.

Tomcat's Clustering / Session Replication not replicating properly

Setup

What's working

What's not working