public static synchronized void shutdownInstance() {
    refCount--;
    if (instance == null) {
      return;
    }
    if (refCount > 0) {
      return;
    }
    instance.shutdown();

    boolean interrupted = false; // Don't clear, let join fail if already interrupted
    try {
      if (instance.clientMonitor != null) {
        instance.clientMonitor.join();
      }
    } catch (InterruptedException e) {
      interrupted = true;
      if (logger.isDebugEnabled()) {
        logger.debug(":Interrupted joining with the ClientHealthMonitor Thread", e);
      }
    } finally {
      if (interrupted) {
        Thread.currentThread().interrupt();
      }
    }
    instance = null;
    refCount = 0;
  }
Shuts down the singleton <code>ClientHealthMonitor</code> instance.
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/ClientHealthMonitor.java