Double Tomcat behind mod_jk load balancer

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"/>