def do_capacity(self, line):
        "capacity {tablename} {read_units} {write_units}"
        args = self.getargs(line)

        table = self.get_table(args[0])
        read_units = int(args[1])
        write_units = int(args[2])

        desc = self.conn.describe_table(table.name)
        prov = desc['Table']['ProvisionedThroughput']

        current_read, current_write = prov['ReadCapacityUnits'], prov['WriteCapacityUnits']
        if read_units < current_read or write_units < current_write:
            table.update_throughput(read_units, write_units)
            print "%s: updating capacity to %d read units, %d write units" % (table.name, read_units, write_units)
            print ""
            self.do_refresh(table.name)

        else:
            print "%s: current capacity is %d read units, %d write units" % (table.name, current_read, current_write)
            # we can only double the current value at each call
            while current_read < read_units or current_write < write_units:
                if (read_units - current_read) > current_read:
                    current_read *= 2
                else:
                    current_read = read_units

                if (write_units - current_write) > current_write:
                    current_write *= 2
                else:
                    current_write = write_units

                print "%s: updating capacity to %d read units, %d write units" % (table.name, current_read, current_write)
                table.update_throughput(current_read, current_write)

                print ""
                self.do_refresh(table.name)
                print ""