CounterMonitor misses events in difference mode

Name: poR10007 Date: 01/22/2004



javax.management.monitor.CounterMonitor (jdk1.5.0-b35) misses
events when run in difference mode. The attached test expects
2 notifications from the monitor but receives only one.
Preliminary analysis shows that eventAlreadyNotified[index] flag
is not always properly restored after a notification has been
emitted.

Please see the test sources and the execution log for details:

---Monitor.java---------------------------------------------------------------
import javax.management.*;
import javax.management.monitor.*;

public class Monitor implements NotificationListener{

    private Number threshold = new Integer(2); // threshold number
    private Number modulus = new Integer(7); // modulus number
    private int offset = 0; // sequence of offset numbers
    private boolean differentmode = true; // with different mode or not
    private boolean isnotified = true; // notification object or not
    private int granularityperiod = 500; // granularity period or sample period for the attribute of the MBean
    private int[] values = new int[] {4, 6}; // counter values
    
    private int timeout = 5; // time to wait for notification (in seconds)
    private volatile boolean messageReceived = false; // flag to notify that a message has been received

    /* Notification handler */
    public void handleNotification(Notification notification, Object handback) {
        
        MonitorNotification notif = (MonitorNotification)notification;
System.out.println("!!! in handleNotification");
        String type = notif.getType();
        try {
            if (type.equals(MonitorNotification.THRESHOLD_VALUE_EXCEEDED)) {
                System.out.println("\n\t>> " + notif.getObservedAttribute() + " has reached the threshold\n");
                messageReceived = true;
                synchronized (this) {
                    notifyAll();
                }
            }
            else {
                System.out.println("\n\t>> Skipping event of type: " + type);
            }
        } catch (Exception e) {
            System.err.println("Error in handleNotification!");
            e.printStackTrace(System.err);
        }
    }


    /*
     * Standalone entry point.
     * Run the test(s) and report to stdout/stderr.
     */
    public static void main (String args[]) {
        Monitor test = new Monitor();
        test.ThresholdNotification();
    } // End of method main.


    public void ThresholdNotification() {

        CounterMonitor counterMonitor = new CounterMonitor();;
        
        try{
            MBeanServer server = MBeanServerFactory.newMBeanServer();

            String domain = server.getDefaultDomain();
            // Create a new CounterMonitor MBean and add it to the MBeanServer.
            System.out.println("\n>>> CREATE a new CounterMonitor MBean:");
            ObjectName counterMonitorName = new ObjectName(domain + ":name=" +"javax.management.monitor.CounterMonitor");
            server.registerMBean(counterMonitor, counterMonitorName);

            System.out.println("\n>>> ADD a listener to the CounterMonitor...");
            counterMonitor.addNotificationListener(this, null, null);
        
            // MANAGEMENT OF A STANDARD MBEAN.
            // Initialize the Standard MBean.
            System.out.println("\n>>> CREATE a new StdObservedObject MBean:");
            ObjectName stdObsObjName = new ObjectName(domain + ":name=" + "StdObservedObject");
            StdObservedObject stdObsObj = new StdObservedObject();
            server.registerMBean(stdObsObj, stdObsObjName);

            System.out.println("\n>>> SET the attributes of the CounterMonitor:");

            counterMonitor.setObservedObject(stdObsObjName);
System.out.println("\tATTRIBUTE \"ObservedObject\" = " + stdObsObjName);

            counterMonitor.setObservedAttribute("NbObjects");
System.out.println("\tATTRIBUTE \"ObservedAttribute\" = NbObjects");

            counterMonitor.setNotify(isnotified);
System.out.println("\tATTRIBUTE \"Notify\" = " + isnotified);

            counterMonitor.setThreshold(threshold);
System.out.println("\tATTRIBUTE \"Threshold\" = " + threshold);

            counterMonitor.setGranularityPeriod(granularityperiod);
System.out.println("\tATTRIBUTE \"GranularityPeriod\" = " + granularityperiod + " miliseconds");

            counterMonitor.setModulus(modulus);
System.out.println("\tATTRIBUTE \"Modulus\" = " + modulus);

            counterMonitor.setDifferenceMode(differentmode);
System.out.println("\tATTRIBUTE \"DifferenceMode\" = " + differentmode);

            System.out.println("\n>>> START the CounterMonitor...");
            counterMonitor.start();
            
            // set initial value
            Integer data = new Integer(0);
            System.out.println("set data = "+ data.intValue());

            Attribute atrib = new Attribute("NbObjects", data);
            server.setAttribute(stdObsObjName, atrib);
            
            // Wait for granularity period (multiplied by 2 for sure)
            Thread.sleep(granularityperiod * 2);
            
            // Loop through the values
            for (int i = 0; i < values.length; i++) {

                data = new Integer(values[i]);
System.out.println("set data = "+ data.intValue());

                atrib = new Attribute("NbObjects", data);
                server.setAttribute(stdObsObjName, atrib);

                System.out.println("doWait in Counter Monitor");
                doWait();

                // comparison for the notifications
                if (messageReceived) {
                    System.out.println("OKAY: Notification received");
                } else {
                    System.out.println("Error: event notification is missed");
                    return;
                }
                messageReceived = false;
            }
        } catch (Exception e){
            e.printStackTrace(System.err);
System.err.println("\n>>> An unexpected error occurred...");
            return;
        } finally {
counterMonitor.stop() ;
        }

        System.out.println("PASSED");
        return;
    }// End of method ThresholdNotification.
    
    
    /*
     * Wait until timeout reached
     */
    void doWait() {
        for (int i = 0; i < timeout; i++) {
            System.out.println("doWait: waiting for " + timeout + " seconds. i = " + i + ", messageReceived = " + messageReceived);
            if (messageReceived) {
               break;
            }
            try {
                synchronized (this) {
                    wait(1000);
                }
            } catch (InterruptedException e) {
            }
        }
    }
}
------------------------------------------------------------------------------

---StdObservedObject.java-----------------------------------------------------
public class StdObservedObject implements StdObservedObjectMBean {

    public Object getNbObjects() {
return count;
    }

    public void setNbObjects(Object n) {
count = n;
    }

    private Object count= null;
}
------------------------------------------------------------------------------

---StdObservedObjectMBean.java------------------------------------------------
public interface StdObservedObjectMBean {
    public Object getNbObjects();
    public void setNbObjects(Object n);
}
------------------------------------------------------------------------------

---log------------------------------------------------------------------------
$ java -version
java version "1.5.0-beta2"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta2-b35)
Java HotSpot(TM) Client VM (build 1.5.0-beta2-b35, mixed mode)
$ javac -d . Monitor.java StdObservedObject.java StdObservedObjectMBean.java
Note: Monitor.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
$ java Monitor

>>> CREATE a new CounterMonitor MBean:

>>> ADD a listener to the CounterMonitor...

>>> CREATE a new StdObservedObject MBean:

>>> SET the attributes of the CounterMonitor:
        ATTRIBUTE "ObservedObject" = DefaultDomain:name=StdObservedObject
        ATTRIBUTE "ObservedAttribute" = NbObjects
        ATTRIBUTE "Notify" = true
        ATTRIBUTE "Threshold" = 2
        ATTRIBUTE "GranularityPeriod" = 500 miliseconds
        ATTRIBUTE "Modulus" = 7
        ATTRIBUTE "DifferenceMode" = true

>>> START the CounterMonitor...
set data = 0
set data = 4
doWait in Counter Monitor
doWait: waiting for 5 seconds. i = 0, messageReceived = false
!!! in handleNotification

        >> NbObjects has reached the threshold

doWait: waiting for 5 seconds. i = 1, messageReceived = true
OKAY: Notification received
set data = 6
doWait in Counter Monitor
doWait: waiting for 5 seconds. i = 0, messageReceived = false
doWait: waiting for 5 seconds. i = 1, messageReceived = false
doWait: waiting for 5 seconds. i = 2, messageReceived = false
doWait: waiting for 5 seconds. i = 3, messageReceived = false
doWait: waiting for 5 seconds. i = 4, messageReceived = false
Error: event notification is missed
$
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