Use Cases and Examples

Example Metrics Reader

An example Metrics Service subscriber can be found in the core module.

package org.cougaar.core.qos.metrics;

/**
 * Basic Metric Service Client subscribes to a Metric path given in
 * the Agent's .ini file and prints the value if it ever changes
 */
public class MetricsClientPlugin 
    extends ParameterizedPlugin
    implements Constants
{
    protected MetricsService metricsService;
    private String paramPath = null;
    private VariableEvaluator evaluator;

  /**
   * Metric CallBack object
   */
    private class MetricsCallback implements Observer {
      /**
       * Call back implementation for Observer
       */

      public void update(Observable obs, Object arg) {
	    if (arg instanceof Metric) {
		Metric metric = (Metric) arg;
		double value = metric.doubleValue();
		System.out.println("Metric "+ paramPath +"=" + metric);
	    }
	}
    }  

  public void load() {
    super.load();
    ServiceBroker sb = getServiceBroker();

    evaluator = new StandardVariableEvaluator(sb);

    metricsService = ( MetricsService)
      sb.getService(this, MetricsService.class, null);
	
    MetricsCallback cb = new MetricsCallback();
    paramPath = getParameter("path");
    // If no path is given, default to the load average of the
    // current Agent.
    if (paramPath == null) 
	paramPath ="$(localagent)"+PATH_SEPR+"LoadAverage";
    
    Object subscriptionKey=metricsService.subscribeToValue(paramPath, cb,
							   evaluator);
  }
}

Example Metrics Writer

An example Metric Service writer has the following form:

package org.cougaar.core.qos.metrics;

public class MetricsTestComponent 
    extends SimplePlugin
    implements Constants
{
    
    public void load() {
	super.load();

	ServiceBroker sb = getServiceBroker();
	MetricsUpdateService updater = (MetricsUpdateService)
	    sb.getService(this, MetricsUpdateService.class, null);

	String key = "Current" +KEY_SEPR+ "Time" +KEY_SEPR+ "Millis";
        // Publish the current time
	Metric m = new MetricImpl(new Long(System.currentTimeMillis()),
				  SECOND_MEAS_CREDIBILITY,
				  "ms",
                                  "MetricsTestComponent");
	updater.updateValue(key, m);
    }
}