  The online algorithm design was proposed to handle the caching problem when
the future information is unknown. And currently, it draws more and more
attentions from the researchers from the areas of microgrid, where the
production of renewables are unpredictable.
  In this note, we present a framework of randomized online algorithm design
for the \textit{simple and tractable} problem. This framework hopes to provide
a tractable design to design a randomized online algorithm, which can be proved
to achieve the best competitive ratio by \textit{Yao's Principle}.
