@Override
  public void contactedBy(ID sender) {
    contactedBy(sender, currentTimeStamp);
  }
Check thread waits on this object for response. It puts requestId in requestIdVsResponse map.
Response will have requestId, which is used to get ResponseObject. Then it is used to notify
waiting thread.
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/fd/GMSHealthMonitor.java