Double Tomcat behind mod_jk load balancer - apache

Question

I am in the process of setting up two Tomcat instances on the same server with an Apache mod_jk load balancer in front of it. I have been using a guide and the Apache Tomcat documentation and stuck to the basic setup suggested. When i try to start up any of the Tomcat instances, i get a BindException from when it tries to start up the SimpleTcpCluster. The error message is "Cannot assign requested address".
I googled for solutions to this issue and came across two suggestions, the first one being to ensure that Java is configured to prefer IPv4 addresses. Tried it - no change. The second suggested to replace the auto value on the address parameter on the Receiver component inside the cluster config (see config below).
<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster" channelSendOptions="8">
<Manager className="org.apache.catalina.ha.session.DeltaManager"
expireSessionsOnShutdown="false"
notifyListenersOnReplication="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"/>
<Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter">
<Transport className="org.apache.catalina.tribes.transport.nio.PooledParallelSender"/>
</Sender>
<Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver"
address="localhost" port="4000" autoBind="100"
selectorTimeout="5000" maxThreads="6"/>
<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"/>
<ClusterListener className="org.apache.catalina.ha.session.JvmRouteSessionIDBinderListener"/>
<ClusterListener className="org.apache.catalina.ha.session.ClusterSessionListener"/>
</Cluster>
I tried changing "auto" to "localhost", which led to a different error message on Tomcat startup, saying "Address already in use :8009".
At this point i really don't know where to look. Is localhost a bad value? Should i be using auto but make a change somewhere else? Is there anyone out there with a little more experience on this that can give me a helping hand?

Answer 1

We got around this issue by changing the address parameter in the Receiver tag inside the Cluster configuration from "auto" to the actual IP address of the server. I was never able to figure out why this was not working and didn't want to spend any more time once we got the calls through.
<Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver"
address="123.123.x.x" port="4000" autoBind="100"
selectorTimeout="5000" maxThreads="6"/>