14.3.3. Identity clustering

JBoss Portal leverages the servlet container authentication for its own authentication mechanism. When the user is authenticated on one particular node he will have to reauthenticate again if a different node of the cluster (during a failover for instance) is used. This is valid only for the FORM based authentication which is the default form of authentication that JBoss Portal uses. Fortunately JBoss provides transparent reauthentication of the user called JBoss clustered SSO. Its configuration can be found in $JBOSS_HOME/server/all/deploy/jboss-web.deployer/server.xml and you will need to uncomment the following valve:
<Valve className="org.jboss.web.tomcat.service.sso.ClusteredSingleSignOn" />
More information can be found here.