class Redis::HashRing

def self.binary_search(ary, value)
  upper = ary.size - 1
  lower = 0
  idx = 0
  while lower <= upper
    idx = (lower + upper) / 2
    comp = ary[idx] <=> value
    if comp == 0
      return idx
    elsif comp > 0
      upper = idx - 1
    else
      lower = idx + 1
    end
  end
  upper = ary.size - 1 if upper < 0
  upper
end