How to find Tomcat cluster members?

[Arthur Eckert]

Hello folks,

is there a way to figure out all cluster members in a Tomcat node? I would like to extend a web application with a view of all active cluster nodes.

Is there also a way to send messages from one node to another, or a multicast message to all nodes? - At the moment I use jgroups to establish a communication between all nodes.

Thank you in advance,
Arthur

[Arthur Eckert]

I found something. Tomcat uses a framework called Apache Tribes (lib directory 'catalina-tribes.jar')

http://tomcat.apache.org/tomcat-7.0-doc/tribes/introduction.html

[Arthur Eckert]

I did a bad workaround for test purpose. If anyone knows a better way please let me know.

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Set;

import javax.management.MBeanServer;
import javax.management.MBeanServerFactory;
import javax.management.ObjectName;

import org.apache.catalina.ha.tcp.SimpleTcpCluster;
import org.apache.tomcat.util.modeler.BaseModelMBean;

import com.sun.jmx.interceptor.DefaultMBeanServerInterceptor;
import com.sun.jmx.mbeanserver.JmxMBeanServer;


public class TomcatClusterUtil {
	
	private MBeanServer mbserver;
	
	private SimpleTcpCluster simpleTcpCluster;
	
	public TomcatClusterUtil() throws Exception {		
      	ArrayList mbservers = MBeanServerFactory.findMBeanServer(null);

      	if (mbservers != null && mbservers.size() > 0) {
        	mbserver = (MBeanServer) mbservers.get(0);
      	}

      	if (mbserver == null) {
      		throw new Exception("Can't find the MBeanServer!");
      	} 
      	
      	if (mbserver != null) {		
	      	Set<ObjectName> objectNameSet = mbserver.queryNames(null, null);
	      	
	      	for (ObjectName objectName : objectNameSet) {
	      		
	      		// Find the right object.
	      		if ("Catalina:type=Cluster".equals(objectName.getCanonicalName())) {
	               JmxMBeanServer jmxMBeanServer = (JmxMBeanServer) mbserver;
		      		
		      		Class<JmxMBeanServer> jmxMBeanServerClass = JmxMBeanServer.class;
		      		Field[] fields = jmxMBeanServerClass.getDeclaredFields();
		      		for (Field field : fields) {
		      			if (!"mbsInterceptor".equals(field.getName())) {
		      				continue;
		      			}
		      			
		      			// Make the field accessible.
		      			field.setAccessible(true);
		      			
		      			DefaultMBeanServerInterceptor mbInterceptor = (DefaultMBeanServerInterceptor)field.get(jmxMBeanServer);
		      			
		      			 // Make the field private.
			            field.setAccessible(false);
		      			
		      			Class<DefaultMBeanServerInterceptor> mbInterceptorClass = DefaultMBeanServerInterceptor.class;
		      			
		      			Method[] methods = mbInterceptorClass.getDeclaredMethods();
		      			for (Method method : methods) {
		      				if (!"getMBean".equals(method.getName())) {
		      					continue;
		      				}
		      				
		      				// Make the field accessible.
		      				method.setAccessible(true);
		      				
		      				Object beanModelObject = method.invoke(mbInterceptor, objectName);
		      				
		      				// Make the field private.
				            method.setAccessible(false);
		      				
				            BaseModelMBean baseModelMBean = (BaseModelMBean)beanModelObject;					      				
		      				
		      				simpleTcpCluster = (SimpleTcpCluster)baseModelMBean.getManagedResource();					      				
		      			}						           
		      		}
	            }	
	        }
      	}
	}
	
	public SimpleTcpCluster getSimpleTcpCluster() {
		return simpleTcpCluster;
	}

}