Using Liferay’s Delta Manager for Improved Session Replication Performance

Liferay 7.4 2023.Q3+/GA92+

To ensure user session data is synchronized across all instances in the cluster, Liferay supports session replication. That way, if one instance fails, user sessions are not lost as they are replicated to other nodes in the cluster. If you are using a DXP cluster on Tomcat, you can use Liferay’s implementation of DeltaManager for improved performance. This is recommended for clusters of five or fewer nodes.

Warning

Liferay’s Delta Manager relies on Tomcat’s session replication, so only Multicast is supported.

Setting Up Session Replication

Replace <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster" /> with the following lines in Liferay Home’s conf/server.xml:

<Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster">
    <Manager className="com.liferay.support.tomcat.session.LiferayDeltaManager" />
    <Channel className="org.apache.catalina.tribes.group.GroupChannel">
        <Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter">
            <Transport className="org.apache.catalina.tribes.transport.nio.PooledParallelSender" timeout="300000" />
        </Sender>
    </Channel>
</Cluster>

In Liferay Home’s /webapps/ROOT/WEB-INF/web.xml, add a <distributable /> tag inside <webapps>. It should look like this:

<web-app id="Liferay_Portal" metadata-complete="true" version="3.0" 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_3_0.xsd">
	   <distributable />
	   <context-param>
		   <param-name>axis.servicesPath</param-name>
		   <param-value>/api/axis/</param-value>
	   </context-param>

In the portal-ext.properties file, add the following properties:
```
portlet.session.replicate.enabled=true
```

Tip

When debugging, you can add logging to Liferay Home’s /webapps/ROOT/WEB-INF/classes/logging.properties:

org.apache.catalina.ha.session.handlers=java.util.logging.ConsoleHandler
org.apache.catalina.ha.session.level=INFO

Repeat steps 1-3 for each node. Be sure to define the cluster settings in portal-ext.properties; set the database connections so that all nodes point to the same database.
Start the servers sequentially. Cluster nodes cannot be started simultaneously, because the process takes time to determine which node is the master node.

Other Optimizations

For session replication to work, all session attributes must implement java.io.Serializable. Also, session replication only applies to user sessions within the same URL. This is because session state is tracked by a domain-specific cookie. For the full benefits of session replication, a load balancer is recommended to direct traffic to the nodes.

If you define custom cluster valves, you must also define the <ReplicationValve> in the <Cluster> element.

Capability: