produced   : 0..39 in order, one key, one partition
processed  : [4, 5, 6, 7, 12, 0, 13, 14, 15, 16, 17, 18, 19, 1, 20, 8, 21, 22, 23, 24, 2, 25, 26, 27, 28, 29, 30, 3, 31, 36, 9, 37, 38, 39, 32, 33, 10, 34, 35, 11]
adjacent pairs that arrived out of order = 9