cache_usage (EstraierPure::Node)

    # File estraierpure.rb, line 802
        def cache_usage()
          @status = -1
          return -1.0 unless @url
          turl = @url + "/cacheusage"
          reqheads = []
          reqheads.push("Authorization: Basic " + Utility::base_encode(@auth)) if @auth
          resbody = StringIO::new
          rv = Utility::shuttle_url(turl, @pxhost, @pxport, @timeout, reqheads, nil, nil, resbody)
          @status = rv
          return -1.0 if rv != 200
          return resbody.string.strip.to_f
        end