Tomcat Cluster

Setup Tomcat Cluster environment

• Please refer to Tomcat Document to set up cluster environment.
• For configuring with Apache http server, refer to
  • How to Run ZK on Apache + Tomcat clustering, Part I
  • How to Run ZK on Apache + Tomcat clustering, Part II

Using more than 3 nodes with ZK

• Use DeltaManager instead of BackupManager, please refer to cluster-manager for more information.

Sample of server.xml

<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster" channelSendOptions="6">
    <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"/>
        <Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver"
            address="auto"
            port="5001"
            selectorTimeout="100"
            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"/>
        <Interceptor className="org.apache.catalina.tribes.group.interceptors.ThroughputInterceptor"/>
    </Channel>

    <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"/>
</Cluster>

Note, if there are multiple tomcat nodes on one machine, the Receiver port (line 14) should be different for each of them.

Additional setting in ZK project

You have to configure the following settings to make ZK project work in a tomcat cluster environment.

web.xml

• Add the distributable element in WEB-INF/web.xml.

<?xml version="1.0"?>
<web-app  xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    version="2.5">

    <distributable/>

</web-app>

zk.xml

• Line 3, turn on Serializable UI Factory for ZK, please refer to this documentation.
• Line 7, if there are more than three Tomcat cluster nodes, or you are using different cluster-manager such as Hazelcast and other solutions instead, you also need to add the cluster session patch settings.

For example,

<zk>
    <system-config>
        <ui-factory-class>org.zkoss.zk.ui.http.SerializableUiFactory</ui-factory-class>
    </system-config>
    <!-- clustering environment, since ZK 5.0.8-->
    <listener>
        <listener-class>org.zkoss.zkplus.cluster.ClusterSessionPatch</listener-class>
    </listener>
</zk>