code: public boolean isOnline(String nodeID) {
  		if (this.nodeID.equals(nodeID)) {
  			return true;
  		}
  		NodeDescriptor node = nodes.get(nodeID);
  		if (node == null) {
  			return false;
  		}
  		node.readLock.lock();
  		try {
  			return node.offlineSince == 0 && node.seq > 0;
  		} finally {
  			node.readLock.unlock();
  		}
  	}
docs: --- IS NODE ONLINE? ---