'Return host uptime for a compute host in a certain cell
:param host_name: fully qualified hostname. It should be in format of
parent!child@host_id'

def get_host_uptime(self, ctxt, host_name):

    (cell_name, host_name) = cells_utils.split_cell_and_item(host_name)
    response = self.msg_runner.get_host_uptime(ctxt, cell_name, host_name)
    return response.value_or_raise()
