When the host is down does not necessarily compute service is down.

[Ratnaker]

During evacuate operation, api checking if the compute service is down. But it is not always the case. There may be instances where compute service is still up when the host is down. for ex: If the compute service is running on a different system rather than on the host itself.

[Ratnaker (ratnaker-katipally)]

The code

        if self.servicegroup_api.service_is_up(service):
            LOG.error(_LE('Instance compute service state on %s '
                          'expected to be down, but it was up.'), inst_host)
            raise exception.ComputeServiceInUse(host=inst_host)

Can be changed to

        if self.servicegroup_api.service_is_up(service):
            LOG.error(_LE('Instance compute service state on %s '
                          'expected to be down, but it was up.'), inst_host)
            #raise exception.ComputeServiceInUse(host=inst_host)
           if host.state is not 'power_off' or 'crashed' or 'error':
                      raise exception.ComputeServiceInUse(host=inst_host)