Cassandra - summary statistics for GC (partial code)

gistfile1.txt

        /* simple use case
		     * using new materialized view instametrics.host_service_value 
		     * for all nodes find max and min and avg values of gc duration for each node and print out.
		     */
		   
		    /* host names table
		     * CREATE TABLE instametrics.host (
    				host text PRIMARY KEY
		     */
		    System.out.println("getting all node names");
		    t1 = System.currentTimeMillis();
		    rs = session.execute("select * from instametrics.host");   
		    System.out.println("Got rows (without fetching) = " + rs.getAvailableWithoutFetching());
		    int i = 0;
		    ArrayList<Double> allMax = new ArrayList<Double>(); // keep track of all max values
		    double overallMin = Double.MAX_VALUE;
		    double overallAvg = 0;
		    double overallSum = 0;
		    long overallCount = 0;
		    double overallMax = Double.MIN_VALUE;
		    for (Row rowN : rs)
		    {
		    		i++;
		    		
		    		String host = rowN.getString(0);
		    		System.out.println(host);
		    		// get min, avg, max values for gc duration for this node
		    		ResultSet summary = session.execute("select min(metric), avg(metric), max(metric) from instametrics.host_service_value where host='"+ host + "' and service='/cassandra/jvm/gc/ConcurrentMarkSweep/lastGc/duration';");
		    		Row arow = summary.one();
		    		System.out.println(arow);
		    		if (arow.isNull(2)) // nothing returned
		    			;
		    		else
		    		{
			    		Double min = arow.getDouble(0);
			    		Double avg = arow.getDouble(1);
			    		Double max = arow.getDouble(2);
			    		// only compute overall results if row has returned non Null values!
			    		overallSum += avg;
			    		if (min < overallMin)
			    			overallMin = min;
			    		if (max > overallMax)
			    			overallMax = max;
			    		allMax.add(max);
			    		overallCount++;
		    		}
		    }
		    t2 = System.currentTimeMillis();
		    time = t2-t1;
		    System.out.println("Total time = " + time + ", nodes = " + i);
		    overallAvg = (double)(overallSum/overallCount);
		    System.out.println("Overall stats: Min = " + overallMin);
		    System.out.println("Overall stats: Avg = " + overallAvg);
		    System.out.println("Overall stats: Max = " + overallMax);
		    Collections.sort(allMax);
		    System.out.println("All max values:" + allMax);