THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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The Tomcat Web container provides a native clustering solution that can be configured through Geronimo by using gbean definitions within |
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Following are parameters or attributes that you will need to configure for a Tomcat native clustering.
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Although sufficient for many applications, Tomcat clusters have some limitations.:
- This feature does not replicate stateful session Enterprise JavaBeans (EJBs). You will have to avoid Do not use stateful session EJBs in your distributed applications.
- This feature does not replicate dynamic updates to the Java Naming and Directory Interface (JNDI). You will have to configure all the JNDI names that are used by your distributed applications in every node of the cluster.
- This feature does not replicate distributable Web applications to other nodes in the cluster. You will have to deploy your distributable Web applications to every node.
A Consider a cluster configuration should be considered when you want to improve the scalability and availability of your Web application. The following sections provide detailed instructions on about how to set up your cluster nodes.
Setting up a clustering environment
Generally, to To set up a small cluster, you will need at least 2 nodes and 1 HTTP server. The HTTP server is used to serve requests from clients and ensure well-balanced traffic load among different nodes. Similarly, each node is configured to use the same logical Tomcat engine and enable session affinity.
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The Tomcat cluster replicates HTTP session data via by memory-to-memory multicast communication.
Every node transmits its session data to every other node in the cluster. This algorithm is efficient only efficient when the clusters are small. If the clusters grow too large, the overhead in storage utilization and network traffic becomes excessive. To avoid excessive overhead, consider dividing your nodes into several smaller clusters.
HTTP session data is replicated among the nodes in the cluster by using a multicast broadcast. All nodes in the cluster must be on the same physical subnet and multicast broadcast must be supported by that subnet.
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- Ensure that every object placed in the HTTP session implements java.io.Serializable. The clustering feature serializes the objects when it distributes them to the other nodes in the cluster.
- The deployment descriptor for your Web application, that is the
web.xmlfile in the Web archive, must indicate that your Web application is distributable. To do this, insert the distributable element in the deployment descriptor.Code Block XML XML borderStylesolid title Excerpt from web.xml borderStyle solid <?xml version="1.0" encoding="ISO-8859-1"?> <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd"> <web-app> <display-name> ... </display-name> <description> ... </description> <distributable> <distributable/> ... </web-app> - Do not use stateful session Enterprise JavaBeans (EJBs). The clustering feature does not replicate stateful EJBs among the nodes in the cluster.
- If your Web application uses a database, make sure the database can be accessed from every node in the cluster can access the database. Ensure that the proper JDBC drivers are installed on every node and that the datasource objects are defined correctly on every node.
- Do not depend on dynamic updates to the Java Naming and Directory Interface (JNDI). You will need to configure all the JNDI names used by your application in every node of the cluster. The clustering feature does not replicate JNDI changes among the nodes in the cluster.
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Support for session affinity, also known as sticky session support, allows a load balancing service to route an HTTP request back to the same node that created the HTTP session associated with that request until that node fails. You must use session affinity if you configure an asynchronous type of session replication. With asynchronous replication, the reply is returned before the HTTP session is replicated so there is always a chance that , and the next request using that session arrives might arrive before the replication is complete. In this case, the only way to ensure that the request is processed using the correct session data is to route the request to the node that sent the reply to the last request and originated the replication to ensure that the request is processed using the correct session data..
In Geronimo servers, users can have the same experiences as in Tomcat Web container to configure session affinity. To enable session affinity, you must modify servel.xml under the <GERONIMO_HOME>/var/catalina directory and configure the <Engine> with a jvmRoute attribute value that is unique for each node in the cluster. The load balancer will return this value in the session cookie or the encoded URL returned to the browser. When a related request arrives, it can use the value to route the request to the correct node. See the following example:
- For every node in the cluster, update
server.xmlas followed follows after the server is stopped:
whereCode Block XML XML borderStyle solid title Excerpt from server.xmlxml borderStyle solid ... <Engine name="Catalina" defaultHost="${ServerHostname}" jvmRoute="nodeId"> ...- nodeId is a node identifier that is unique among all the nodes in the cluster. If you are using mod_jk, make sure that the jvmRoute attribute value matches your worker name in
workers.properties.
- nodeId is a node identifier that is unique among all the nodes in the cluster. If you are using mod_jk, make sure that the jvmRoute attribute value matches your worker name in
- Restart the server to enable the new configuration.
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Configuring the cluster at application level
To configure applicaiton application level clustering, you have to input all related GBean settings in your deployment plan to make sure HTTP sessions are replicated successfully. Moreover, you must use the gbean definitions within deployment plans to configure the cluster configuration elements of Tomcat Web containers must be configured using gbean definitions within deployment plans. If you want to deploy your Web application to a cluster, install your WAR files to the appropriate cluster member, assuring that you use the correct deployment plan for each member.
Sample Tomcat clustering with multicast Configuration
Here is the The template for your Web application deployment plan is shown as follows. See Creating deployment plans for Web applications for more information about the parameters.
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<web-app xmlns="http://geronimo.apache.org/xml/ns/j2ee/web/tomcat-1.2"
xmlns:dep="http://geronimo.apache.org/xml/ns/deployment-1.2">
<dep:environment>
<dep:moduleId>
<dep:groupId>org.mygroup</dep:groupId>
<dep:artifactId>web-cluster-server1</dep:artifactId>
<dep:version>2.2</dep:version>
<dep:type>war</dep:type>
</dep:moduleId>
<dep:dependencies>
<dep:dependency>
<dep:groupId>console.realm</dep:groupId>
<dep:artifactId>geronimo-properties-realm</dep:artifactId>
<dep:version>1.0</dep:version>
<dep:type>car</dep:type>
</dep:dependency>
</dep:dependencies>
<dep:hidden-classes/>
<dep:non-overridable-classes/>
</dep:environment>
<context-root>/servlet-examples-cluster</context-root>
<security-realm-name>geronimo-properties-realm</security-realm-name>
<security>
<default-principal>
<principal name="anonymous" class="org.apache.geronimo.security.realm.providers.GeronimoUserPrincipal"/>
</default-principal>
<role-mappings>
<role role-name="tomcat">
<principal name="admin" class="org.apache.geronimo.security.realm.providers.GeronimoGroupPrincipal"/>
</role>
</role-mappings>
</security>
<cluster>TomcatCluster</cluster>
<gbean class="org.apache.geronimo.tomcat.cluster.CatalinaClusterGBean" name="TomcatCluster">
<attribute name="className">org.apache.catalina.ha.tcp.SimpleTcpCluster</attribute>
<attribute name="initParams"/>
<reference name="ClusterManager">
<name>TomcatClusterManager</name>
</reference>
<reference name="TomcatValveChain">
<name>ReplicationValve</name>
</reference>
<reference name="ClusterListenerChain">
<name>ClusterSessionListener</name>
</reference>
<reference name="Channel">
<name>TomcatGroupChannel</name>
</reference>
</gbean>
<!-- Cluster Manager -->
<gbean name="TomcatClusterManager" class="org.apache.geronimo.tomcat.cluster.ClusterManagerGBean">
<attribute name="className">org.apache.catalina.ha.session.DeltaManager</attribute>
<attribute name="initParams">name=${clusterName}
channelSendOptions=6
expireSessionsOnShutdown=false
notifyListenersOnReplication=true
mapSendOptions=6</attribute>
</gbean>
<!-- Cluster Channel -->
<gbean class="org.apache.geronimo.tomcat.cluster.ChannelGBean" name="TomcatGroupChannel">
<attribute name="className">org.apache.catalina.tribes.group.GroupChannel</attribute>
<attribute name="initParams"/>
<reference name="Membership">
<name>TomcatMembership</name>
</reference>
<reference name="Receiver">
<name>TomcatReceiver</name>
</reference>
<reference name="Sender">
<name>TomcatSender</name>
</reference>
<reference name="ChannelInterceptor">
<name>TomcatChannelInterceptor</name>
</reference>
</gbean>
<!-- Cluster Membership -->
<gbean class="org.apache.geronimo.tomcat.cluster.MembershipServiceGBean" name="TomcatMembership">
<attribute name="className">org.apache.catalina.tribes.membership.McastService</attribute>
<attribute name="initParams">
mcastAddr=228.0.0.4
mcastPort=45564
mcastFrequency=500
mcastDropTime=3000
</attribute>
</gbean>
<!-- Cluster Receiver -->
<gbean class="org.apache.geronimo.tomcat.cluster.ReceiverGBean" name="TomcatReceiver">
<attribute name="className">org.apache.catalina.tribes.transport.nio.NioReceiver</attribute>
<attribute name="initParams">
tcpListenAddress=auto
tcpListenPort=4001
tcpSelectorTimeout=100
tcpThreadCount=6
</attribute>
</gbean>
<!-- Cluster Sender -->
<gbean class="org.apache.geronimo.tomcat.cluster.SenderGBean" name="TomcatSender">
<attribute name="className">org.apache.catalina.tribes.transport.ReplicationTransmitter</attribute>
<attribute name="initParams">
replicationMode=pooled
waitForAck=true
</attribute>
</gbean>
<!-- Cluster Valves-->
<gbean class="org.apache.geronimo.tomcat.ValveGBean" name="ReplicationValve">
<attribute name="className">org.apache.catalina.ha.tcp.ReplicationValve</attribute>
<attribute name="initParams">filter=.*\.gif;.*\.js;.*\.css;.*\.png;.*\.jpeg;.*\.jpg;.*\.htm;.*\.html;.*\.txt;</attribute>
<reference name="NextValve">
<name>JvmRouteBinderValve</name>
</reference>
</gbean>
<!-- Cluster Route Binder -->
<gbean class="org.apache.geronimo.tomcat.ValveGBean" name="JvmRouteBinderValve">
<attribute name="className">org.apache.catalina.ha.session.JvmRouteBinderValve</attribute>
<attribute name="initParams">enabled=true</attribute>
</gbean>
<!-- Cluster Listener -->
<gbean class="org.apache.geronimo.tomcat.cluster.ClusterListenerGBean" name="ClusterSessionListener">
<attribute name="className">org.apache.catalina.ha.session.ClusterSessionListener</attribute>
<reference name="NextListener">
<name>JvmRouteSessionIDBinderListener</name>
</reference>
</gbean>
<!-- Cluster Binder Listener-->
<gbean class="org.apache.geronimo.tomcat.cluster.ClusterListenerGBean" name="JvmRouteSessionIDBinderListener">
<attribute name="className">org.apache.catalina.ha.session.JvmRouteSessionIDBinderListener</attribute>
</gbean>
<!-- Cluster Channel Interceptor -->
<gbean class="org.apache.geronimo.tomcat.cluster.ChannelInterceptorGBean" name="TomcatChannelInterceptor">
<attribute name="className">org.apache.catalina.tribes.group.interceptors.TcpFailureDetector</attribute>
</gbean>
</web-app>
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On each node, deploy your Web application, by using either via admin the administration console or the deploy command, following this syntax:
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- name is replaced with a user name authorized to manage the server. If you omit this option, you will be prompted to enter a user name.
- word is replaced with the password used to authenticate the user. If you omit this option, you will be prompted to enter a password.
- archive is replaced with a file specification to your Web application WAR file.
- plan is replaced with a file specification to your deployment plan.
Note: After the server installation, the default user name is initially system, and the default password is manager.
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The following code snippet is part of a clustering example that uses unicast configuration. Static members are defined using org.apache.geronimo.tomcat.cluster.StaticMemberGBean. You have to define each static member within your deployment plan to make sure that your application is clustered successfully, and make sure that TCP ports for session replication are defined consistently on each node.
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<cluster>TomcatCluster</cluster>
<gbean name="TomcatCluster" class="org.apache.geronimo.tomcat.cluster.CatalinaClusterGBean">
<attribute name="className">org.apache.catalina.ha.tcp.SimpleTcpCluster</attribute>
<attribute name="initParams"/>
<reference name="ClusterListenerChain">
<name>TomcatClusterListenerChain</name>
</reference>
<reference name="TomcatValveChain">
<name>ReplicationValve</name>
</reference>
<reference name="Channel">
<name>TomcatChannel</name>
</reference>
<reference name="ClusterManager">
<name>TomcatClusterManager</name>
</reference>
</gbean>
<gbean name="TomcatClusterListenerChain" class="org.apache.geronimo.tomcat.cluster.ClusterListenerGBean">
<attribute name="className">org.apache.catalina.ha.session.ClusterSessionListener</attribute>
<attribute name="initParams"/>
</gbean>
<gbean name="ReplicationValve" class="org.apache.geronimo.tomcat.ValveGBean">
<attribute name="className">org.apache.catalina.ha.tcp.ReplicationValve</attribute>
<attribute name="initParams">.*\.gif;.*\.js;.*\.jpg;.*\.png;.*\.htm;.*\.html;.*\.css;.*\.txt;</attribute>
<reference name="NextValve">
<type>TomcatValve</type>
<name>JvmRouteBinderValve</name>
</reference>
</gbean>
<gbean name="JvmRouteBinderValve" class="org.apache.geronimo.tomcat.ValveGBean">
<attribute name="className">org.apache.catalina.ha.session.JvmRouteBinderValve</attribute>
<attribute name="initParams">enabled=true</attribute>
</gbean>
<gbean name="TomcatClusterManager" class="org.apache.geronimo.tomcat.cluster.ClusterManagerGBean">
<attribute name="className">org.apache.catalina.ha.session.DeltaManager</attribute>
<attribute name="initParams">name=${clusterName}
channelSendOptions=6
expireSessionsOnShutdown=false
notifyListenersOnReplication=true
mapSendOptions=6
</attribute>
</gbean>
<gbean name="TomcatChannel" class="org.apache.geronimo.tomcat.cluster.ChannelGBean">
<attribute name="className">org.apache.catalina.tribes.group.GroupChannel</attribute>
<attribute name="initParams"/>
<reference name="Membership">
<name>ClusterMembership</name>
</reference>
<reference name="Receiver">
<name>ClusterReceiver</name>
</reference>
<reference name="Sender">
<name>ClusterSender</name>
</reference>
<reference name="ChannelInterceptor">
<name>DisableMcastInterceptor</name>
</reference>
</gbean>
<gbean name="ClusterMembership" class="org.apache.geronimo.tomcat.cluster.MembershipServiceGBean">
<attribute name="className">org.apache.catalina.tribes.membership.McastService</attribute>
<attribute name="initParams">address=228.0.0.4
port=45564
frequency=500
dropTime=3000
</attribute>
</gbean>
<gbean name="ClusterReceiver" class="org.apache.geronimo.tomcat.cluster.ReceiverGBean">
<attribute name="className">org.apache.catalina.tribes.transport.nio.NioReceiver</attribute>
<attribute name="initParams">address=IPAddress1
port=TCP_port1
selectorTimeout=100
maxThreads=6
</attribute>
</gbean>
<gbean name="ClusterSender" class="org.apache.geronimo.tomcat.cluster.SenderGBean">
<attribute name="className">org.apache.catalina.tribes.transport.ReplicationTransmitter</attribute>
</gbean>
<gbean name="DisableMcastInterceptor" class="org.apache.geronimo.tomcat.cluster.ChannelInterceptorGBean">
<attribute name="className">org.apache.geronimo.tomcat.interceptor.DisableMcastInterceptor</attribute>
<attribute name="initParams"/>
<reference name="NextInterceptor">
<name>TcpPingInterceptor</name>
</reference>
</gbean>
<gbean name="TcpPingInterceptor" class="org.apache.geronimo.tomcat.cluster.ChannelInterceptorGBean">
<attribute name="className">org.apache.catalina.tribes.group.interceptors.TcpPingInterceptor</attribute>
<attribute name="initParams">Interval=60</attribute>
<reference name="NextInterceptor">
<name>TcpFailureDetector</name>
</reference>
</gbean>
<gbean name="TcpFailureDetector" class="org.apache.geronimo.tomcat.cluster.ChannelInterceptorGBean">
<attribute name="className">org.apache.catalina.tribes.group.interceptors.TcpFailureDetector</attribute>
<attribute name="initParams"/>
<reference name="NextInterceptor">
<name>StaticMember1Interceptor</name>
</reference>
</gbean>
<gbean name="StaticMember1Interceptor" class="org.apache.geronimo.tomcat.cluster.ChannelInterceptorGBean">
<attribute name="className">org.apache.catalina.tribes.group.interceptors.StaticMembershipInterceptor</attribute>
<attribute name="initParams"/>
<reference name="StaticMember">
<name>StaticMember2</name>
</reference>
<reference name="NextInterceptor">
<name>MessageDispatch15Interceptor</name>
</reference>
</gbean>
<gbean name="MessageDispatch15Interceptor" class="org.apache.geronimo.tomcat.cluster.ChannelInterceptorGBean">
<attribute name="className">org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor</attribute>
<attribute name="initParams"/>
<reference name="NextInterceptor">
<name>ThroughputInterceptor</name>
</reference>
</gbean>
<gbean name="ThroughputInterceptor" class="org.apache.geronimo.tomcat.cluster.ChannelInterceptorGBean">
<attribute name="className">org.apache.catalina.tribes.group.interceptors.ThroughputInterceptor</attribute>
<attribute name="initParams"/>
</gbean>
<gbean name="StaticMember2" class="org.apache.geronimo.tomcat.cluster.StaticMemberGBean">
<attribute name="className">org.apache.catalina.tribes.membership.StaticMember</attribute>
<attribute name="initParams">port=TCP_port2
securePort=-1
host=IPAddress2
domain=test-domain
UniqueId={2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
</attribute>
</gbean>
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- IPAddress1 is the IP address or host name of the current static member.
- TCP_port1 is the TCP port on the current node to listen for session replication data from other static members.
- IPAddress2 is the IP address or host name of the second static member.
- TCP_port2 is the TCP port on the second static member to listen for session replication data from other static members
To convert this example to a multicast configuration, removed the DisableMCastInterceptor, StaticMemberInterceptor, and StaticMember definitions need to be removed. Also, change the value for the "address" attribute for the TomcatReceiver definition should be changed to "auto".
Configuring the cluster at
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Engine or Host level
You can configure the cluster just like you always did for a standalone Tomcat Web container, input . Input all the clustering configuration into the var/catalina/server.xml file according to your requirement requirements in Geronimo. Both multicast and unicat are supported well. Refer to See the following sample codes when you want to configure a Enginee/an Engine or Host level cluster, make . Make sure that these segments are enclosed within <Enginee> the <Engine> or <Host> element in server.xml. ${clusterName} is from var/config/config-substitutions.properties, which should be identical within all nodes in a cluster.
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- IPAddress is the IP address or host name of the second static member.
- TCP_port is the TCP port on the second static member to listen for session replication data from other static members.