OSGi bundle CPU usage

Question : how to compute the CPU used by an OSGi bundle ?

Answer :
- manage a Map table for the threads list owned by any given OSGi bundle
- rely on the JMX standard API


Details :

Step #1 : consider these attributes, based on JMX Beans :

private Map<Bundle, ArrayList<Thread>> threadMap =
    new HashMap<Bundle, ArrayList<Thread>>();
private Map<Long, Long> threadTime =
    new HashMap<Long, Long>();
private RuntimeMXBean runTimeBean =
    ManagementFactory.getRuntimeMXBean();
private ThreadMXBean threadBean =
    ManagementFactory.getThreadMXBean();
private int nbProcs =
    ManagementFactory.getOperatingSystemMXBean().getAvailableProcessors();
private long timerStart;
private long timerDelay;

Where 'timerStart' and 'timerDelay' should be updated as follows :

timerStart = runTimeBean.getUptime(); // init time
timerDelay = (runTimeBean.getUptime() - timerStart) * 1000000L; // window time

Step #2 : assuming that the 2 Map instances are being successfully maintained while any bundle is getting started/stopped on the OSGi framework, the percentage of CPU used by a given bundle can be computed as follows :

/**
* Get the percentage of CPU used by a bundle
*
* @param bundle
* The monitored bundle instance
* @return The percentage of CPU used
*/
private float getBundlePercentTime(Bundle bundle)
{
    long cpuTime     = 0L; // CPU used in nanoseconds
    float cpuPercent = 0F; // percentage of CPU used

    if ((cpuTime = getBundleCpuTime(bundle)) > 0)
    {
        cpuPercent = Math.min(0.99F, (float) cpuTime / (float) timerDelay);
    }

    return cpuPercent * 100.0F;
}


/**
* Get the overall CPU used by a bundle
*
* @param bundle
* The monitored bundle instance
* @return Its actual CPU usage in nanoseconds
*/
private long getBundleCpuTime(Bundle bundle)
{
    long cpuTime = 0L; // CPU used in nanoseconds

    if (threadMap.containsKey(bundle))
    {
        for (Thread thread : threadMap.get(bundle))
    {
        cpuTime += updateThreadCpuTime(thread.getId());
    }
    }
    else
    {
        // Error handling
    }

    return cpuTime;
}


/**
* Refresh the CPU used by a thread, given its identifier
*
* @param threadID
* The monitored thread identifier
* @return Its actual CPU usage in nanoseconds
*/
private long updateThreadCpuTime(long threadID)
{
    long diffCpu      = 0L; // actual CPU difference in nanoseconds
    long currentCpu   = 0L; // actual CPU in nanoseconds
    long previousCpu  = 0L; // previous CPU in nanoseconds
    Long previousCpuL = 0L; // previous CPU in nanoseconds

    // Compute actual CPU usage
    if ((previousCpuL = threadTime.get(threadID)) != null)
    previousCpu = previousCpuL.longValue();
    if ((currentCpu = threadBean.getThreadCpuTime(threadID)) >= 0)
    diffCpu = currentCpu - previousCpu;

    // Map table update
    threadTime.put(threadID, currentCpu);

    return diffCpu;
}