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Sun GlassFish Communications Server 2.0 High Availability Administration Guide

Creating a Data Centric Rules JAR File

The data centric rules of the converged load balancer is configurable using an implementation of the org.glassfish.comms.api.datacentric.DcrPlugin interface , which is supplied as a pre-compiled Java class packaged in a JAR file. When routing a request, the converged load balancer calls the instantiated plug-in to extract the key from initial SIP and HTTP requests. The converged load balancer uses the result returned from the plug-in, to lookup the serving instance in the consistent hash.

The org.glassfish.comms.api.datacentric.DcrPlugin interface specifies two methods:

You can implement these methods to extract the key to be used for lookup in the consistent hash in the converged load balancer, for initial requests. Each method can return a non-null value, which indicates that the request matches a rule and a hash key is successfully extracted. If none of the rules match a request, a null value is returned and the hash key is extracted using default rules.

To facilitate the implementation of the data centric rules plug-in, the following entities are provided as method arguments:

The data centric rules JAR file must contain a compiled implementation of the plug-in interface. It can also contain other application specific helper classes. It must also have a manifest that specifies the class name of this data centric rules plug-in implementation. The converged load balancer uses the manifest to identify the class that implements data centric rules plug-in. It then loads the plug-in class and creates an instance.

Here is an example Java class file that specifies data centric rules:

package mydcr;

import org.glassfish.comms.api.datacentric.DcrPlugin;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.sip.SipFactory;
import javax.servlet.sip.SipServletRequest;
import javax.servlet.sip.SipURI;
import org.glassfish.comms.api.telurl.TelUrlResolver;
import org.glassfish.comms.api.uriutils.UriTools;

public class MyDcrPluginImpl implements DcrPlugin{

    public String getKey(SipServletRequest request,
            SipFactory sipFactory, UriTools uriTools,
            TelUrlResolver telUrlResolver) {
        String key = null;
        String method = request.getMethod().toUpperCase();
        if(method.equals( "PUBLISH" ) || method.equals( "INVITE" ) 
              || method.equals( "CANCEL" )){
           key = SipURI.class.cast(request.getTo().getURI()).getUser();
        } else if (method.equals( "REGISTER" )
                || method.equals( "SUBSCRIBE" )){
            key = SipURI.class.cast(request.getFrom().getURI()).getUser();
        }
        System.out.println("MY DCR PLUGIN - Key extracted from SIP request : " + key);
        return key;
    }

    public String getKey(HttpServletRequest request,
            SipFactory sipFactory, UriTools uriTools,
            TelUrlResolver telUrlResolver) {
        String key =  request.getParameter( "j_username" );
        System.out.println("MY DCR PLUGIN - Key extracted from HTTP request : " + key);
        return key;
    }


}

After you have written the data centric rules class, follow these steps:

  1. Compile the data centric rules class as shown in the following example command. You must include ssa-api.jar, javaee.jar, and comms-appserv-api.jar in the classpath. The classes directory must exist.


    javac -classpath as-install/lib/ssa-api.jar:as-install/lib/javaee.jar:as-install/lib/comms-appserv-api.jar 
-d classes src/mydcr/MyDcrPluginImpl.java

  2. Write the manifest file. For example:

    Manifest-Version: 1.0
Dcr-Plugin-Class: mydcr.MyDcrPluginImpl

  3. Create the data centric rules JAR file. For example:


    jar -cvfm mydcrplugin.jar mymanifest -C classes mydcr/MyDcrPluginImpl.class

  4. Set the data centric rules file using the asadmin set-dcr-file command. Refer the instructions at Setting the Data Centric Rules File for a Converged Load Balancer.