protected static synchronized void createInstance(InternalCache cache,
      int maximumTimeBetweenPings, CacheClientNotifierStats stats) {
    refCount++;
    if (instance != null) {
      return;
    }
    instance = new ClientHealthMonitor(cache, maximumTimeBetweenPings, stats);
  }
Creates the singleton <code>CacheClientNotifier</code> instance.

@param cache The GemFire <code>Cache</code>
@param maximumTimeBetweenPings The maximum time allowed between pings before determining the
       client has died and interrupting its sockets
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/ClientHealthMonitor.java