ZK Installation Guide/Setting up Servers/Tomcat Cluster

Setup Tomcat Cluster environment

• 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

• Using DeltaManager instead of BackupManager, 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.

Additional setting in ZK project

You have to configure the following settings to make ZK project work in 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

• Turn on Serializable UI Factory for ZK, please refer to this documentation.
• If Tomcat cluster nodes is large than 3, also need to add cluster session patch.

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>