@Override
    public int getActiveCount() {
        return (int)(startedCount.get() - completedCount.get());
    }
A thread pool executor which maintains the last time a worker completed.

@author Steinar Knutsen
@author baldersheim
@author bratseth
container-core/src/main/java/com/yahoo/container/handler/threadpool/WorkerCompletionTimingThreadPoolExecutor.java