Configuring a Simple tc Server Cluster

This following procedure describes how to set up a simple tc Server cluster that uses default values for most configuration options. See the section after the procedure for a description of this default cluster configuration.

For each tc Server instance that will be a member of the cluster, update its CATALINA_BASE/conf/server.xml by adding a <Cluster> child-element of the <Engine> element, as shown in the following example (only relevant sections shown):
```
<?xml version='1.0' encoding='utf-8'?>
<Server port="-1" shutdown="SHUTDOWN">
  ...
  <Service name="Catalina">
    ...
    <Engine name="Catalina" defaultHost="localhost">
        <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>
        ...
    </Engine> 
  </Service>
</Server> 
```
The server.xml file for many tc Server instances already contains a commented-out <Cluster>; in which case, simply remove the comment tags.

You can also add the <Cluster> element to the <Host> element of the server.xml file, which means that you want enable clustering in all the virtual hosts of tc Server. When you add the <Cluster> element inside the <Engine> element, the cluster appends the host name of each session manager to the manager'ss name so that two contexts with the same name but sitting inside two different hosts are distinguishable.
If you are going to run more than one tc Server instance on the same computer, be sure the various TCP/IP listen ports for each tc Server instance are unique. You configure the listen ports using the port and redirectPort attributes of the <Connector> element in the server.xml file. See Simple tc Server Configuration.
If you are going to run more than one tc Server instance on the same computer, and you are using AMS to monitor and configure the cluster and its individual members, be sure the JMX listen ports for each tc Server instance are unique. You configure the JMX listen port using the port attribute of the <Listener classname="com.springsource.tcserver.serviceability.rmi.JmxSocketListener"> element in the server.xml file. See Simple tc Server Configuration.
If the cluster is hosted on more than one computer, be sure that all computers are time-sychronized. Use the Network Time Protocol (NTP) to synchronize the computers; see The Network Time Protocol for details.

The cluster that results from the proceding procedure will have the following configuration:

The cluster is enabled with all-to-all session replication, which means that when a session on one member of the cluster is modified by the client, the session changes are replicated to all other members of the cluster, even members in which the application is not deployed. This is the recommended session replication scheme for small clusters, but as the cluster starts to get bigger with more and more members, SpringSource recommends you use a primary-secondary replication scheme in which session data is replicated to a single backup member, and only to members in which the application is deployed. See Replicating a Session to a Single Backup Member.
The multicast address is 228.0.0.4.
The multicast port is 45564.
The members of the cluster send out heartbeats (to broadcast that they are alive and well) every 500 milliseconds.
If a heartbeat is not received from a member of the cluster after 3000 milliseconds, the cluster is notified and the member may be marked as failed.
The IP address that members of the cluster broadcast to the other members is the local value of java.net.InetAddress.getLocalHost().getHostAddress().
The TCP/IP port that members use to listen for replication messages is the first available server socket in range 4000-4100.

For additional detailed information about tc Server clusters and a description of the default cluster configuration, see Clustering/Session Replication HOW-TO.