code: private boolean setAvailable(NodeStatus nodeStatus, boolean isAvailable) {
          synchronized(nodeStatus) {
              boolean previous = nodeStatus.isAvailable();
  
              nodeStatus.setAvailable(isAvailable);
              nodeStatus.setLastChecked(getConfig().getTime().getMilliseconds());
  
              return previous;
          }
      }
docs: We need to distinguish the case where we're newly available and the case
  where we're already available. So we check the node status before we
  update it and return it to the caller.
  
  @param isAvailable True to set to available, false to make unavailable
  
  @return Previous value of isAvailable