http://www.datastax.com/dev/blog/new-metrics-in-cassandra12

MANIFEST.MF

Manifest-Version: 1.0
Premain-Class: com.datastax.example.ReportAgent

ReportAgent.java

package com.datastax.example;

import java.lang.instrument.Instrumentation;
import java.util.concurrent.TimeUnit;

import com.yammer.metrics.reporting.GraphiteReporter;

public class ReportAgent
{
    public static void premain(String agentArgs, Instrumentation inst)
    {
        // reports metrics to Graphite at 127.0.0.1:2003, every 60 seconds
        GraphiteReporter.enable(60, TimeUnit.SECONDS, "127.0.0.1", 2003);
    }
}