Add --by-service to discover_hosts
This allows us to discover and map compute hosts by service instead of by compute node, which will solve a major deployment ordering problem for people using ironic. This also allows closing a really nasty race when doing HA of nova-compute/ironic. Change-Id: Ie9f064cb9caf6dcba2414acb24d12b825df45fab Closes-Bug: #1755602
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Dan Smith
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@ -199,7 +199,7 @@ Nova Cells v2
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database connection was missing, and 2 if a cell is already using that
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transport url and database connection combination.
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``nova-manage cell_v2 discover_hosts [--cell_uuid <cell_uuid>] [--verbose] [--strict]``
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``nova-manage cell_v2 discover_hosts [--cell_uuid <cell_uuid>] [--verbose] [--strict] [--by-service]``
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Searches cells, or a single cell, and maps found hosts. This command will
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check the database for each cell (or a single one if passed in) and map any
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hosts which are not currently mapped. If a host is already mapped nothing
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@ -208,7 +208,11 @@ Nova Cells v2
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there and the API will not list the new hosts). If the strict option is
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provided the command will only be considered successful if an unmapped host
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is discovered (exit code 0). Any other case is considered a failure (exit
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code 1).
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code 1). If --by-service is specified, this command will look in the
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appropriate cell(s) for any nova-compute services and ensure there are host
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mappings for them. This is less efficient and is only necessary when using
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compute drivers that may manage zero or more actual compute nodes at any
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given time (currently only ironic).
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``nova-manage cell_v2 list_cells [--verbose]``
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Lists the v2 cells in the deployment. By default only the cell name and
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@ -1349,7 +1349,11 @@ class CellV2Commands(object):
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help=_('Considered successful (exit code 0) only when an unmapped '
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'host is discovered. Any other outcome will be considered a '
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'failure (exit code 1).'))
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def discover_hosts(self, cell_uuid=None, verbose=False, strict=False):
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@args('--by-service', action='store_true', default=False,
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dest='by_service',
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help=_('Discover hosts by service instead of compute node'))
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def discover_hosts(self, cell_uuid=None, verbose=False, strict=False,
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by_service=False):
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"""Searches cells, or a single cell, and maps found hosts.
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When a new host is added to a deployment it will add a service entry
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@ -1362,7 +1366,8 @@ class CellV2Commands(object):
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print(msg)
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ctxt = context.RequestContext()
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hosts = host_mapping_obj.discover_hosts(ctxt, cell_uuid, status_fn)
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hosts = host_mapping_obj.discover_hosts(ctxt, cell_uuid, status_fn,
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by_service)
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# discover_hosts will return an empty list if no hosts are discovered
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if strict:
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return int(not hosts)
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@ -175,7 +175,7 @@ class HostMappingList(base.ObjectListBase, base.NovaObject):
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return base.obj_make_list(context, cls(), HostMapping, db_mappings)
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def _check_and_create_host_mappings(ctxt, cm, compute_nodes, status_fn):
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def _check_and_create_node_host_mappings(ctxt, cm, compute_nodes, status_fn):
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host_mappings = []
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for compute in compute_nodes:
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status_fn(_("Checking host mapping for compute host "
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@ -197,7 +197,41 @@ def _check_and_create_host_mappings(ctxt, cm, compute_nodes, status_fn):
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return host_mappings
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def discover_hosts(ctxt, cell_uuid=None, status_fn=None):
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def _check_and_create_service_host_mappings(ctxt, cm, services, status_fn):
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host_mappings = []
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for service in services:
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try:
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HostMapping.get_by_host(ctxt, service.host)
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except exception.HostMappingNotFound:
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status_fn(_('Creating host mapping for service %(srv)s') %
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{'srv': service.host})
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host_mapping = HostMapping(
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ctxt, host=service.host,
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cell_mapping=cm)
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host_mapping.create()
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host_mappings.append(host_mapping)
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return host_mappings
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def _check_and_create_host_mappings(ctxt, cm, status_fn, by_service):
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from nova import objects
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if by_service:
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services = objects.ServiceList.get_by_binary(
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ctxt, 'nova-compute', include_disabled=True)
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added_hm = _check_and_create_service_host_mappings(ctxt, cm,
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services,
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status_fn)
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else:
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compute_nodes = objects.ComputeNodeList.get_all_by_not_mapped(
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ctxt, 1)
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added_hm = _check_and_create_node_host_mappings(ctxt, cm,
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compute_nodes,
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status_fn)
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return added_hm
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def discover_hosts(ctxt, cell_uuid=None, status_fn=None, by_service=False):
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# TODO(alaski): If this is not run on a host configured to use the API
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# database most of the lookups below will fail and may not provide a
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# great error message. Add a check which will raise a useful error
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@ -220,21 +254,19 @@ def discover_hosts(ctxt, cell_uuid=None, status_fn=None):
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status_fn(_('Skipping cell0 since it does not contain hosts.'))
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continue
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if 'name' in cm and cm.name:
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status_fn(_("Getting compute nodes from cell '%(name)s': "
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status_fn(_("Getting computes from cell '%(name)s': "
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"%(uuid)s") % {'name': cm.name,
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'uuid': cm.uuid})
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else:
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status_fn(_("Getting compute nodes from cell: %(uuid)s") %
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status_fn(_("Getting computes from cell: %(uuid)s") %
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{'uuid': cm.uuid})
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with context.target_cell(ctxt, cm) as cctxt:
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compute_nodes = objects.ComputeNodeList.get_all_by_not_mapped(
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cctxt, 1)
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added_hm = _check_and_create_host_mappings(cctxt, cm, status_fn,
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by_service)
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status_fn(_('Found %(num)s unmapped computes in cell: %(uuid)s') %
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{'num': len(compute_nodes),
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{'num': len(added_hm),
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'uuid': cm.uuid})
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added_hm = _check_and_create_host_mappings(cctxt, cm,
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compute_nodes,
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status_fn)
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host_mappings.extend(added_hm)
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return host_mappings
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@ -240,3 +240,73 @@ class TestHostMappingDiscovery(test.NoDBTestCase):
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self.assertTrue(mock_hm_create.called)
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self.assertEqual(['d'],
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[hm.host for hm in hms])
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@mock.patch('nova.objects.CellMappingList.get_all')
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@mock.patch('nova.objects.HostMapping.get_by_host')
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@mock.patch('nova.objects.HostMapping.create')
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@mock.patch('nova.objects.ServiceList.get_by_binary')
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def test_discover_services(self, mock_srv, mock_hm_create,
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mock_hm_get, mock_cm):
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mock_cm.return_value = [
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objects.CellMapping(uuid=uuids.cell1),
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objects.CellMapping(uuid=uuids.cell2),
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]
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mock_srv.side_effect = [
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[objects.Service(host='host1'),
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objects.Service(host='host2')],
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[objects.Service(host='host3')],
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]
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def fake_get_host_mapping(ctxt, host):
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if host == 'host2':
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return
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else:
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raise exception.HostMappingNotFound(name=host)
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mock_hm_get.side_effect = fake_get_host_mapping
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ctxt = context.get_admin_context()
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mappings = host_mapping.discover_hosts(ctxt, by_service=True)
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self.assertEqual(2, len(mappings))
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self.assertEqual(['host1', 'host3'],
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sorted([m.host for m in mappings]))
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@mock.patch('nova.objects.CellMapping.get_by_uuid')
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@mock.patch('nova.objects.HostMapping.get_by_host')
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@mock.patch('nova.objects.HostMapping.create')
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@mock.patch('nova.objects.ServiceList.get_by_binary')
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def test_discover_services_one_cell(self, mock_srv, mock_hm_create,
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mock_hm_get, mock_cm):
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mock_cm.return_value = objects.CellMapping(uuid=uuids.cell1)
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mock_srv.return_value = [
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objects.Service(host='host1'),
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objects.Service(host='host2'),
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]
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def fake_get_host_mapping(ctxt, host):
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if host == 'host2':
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return
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else:
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raise exception.HostMappingNotFound(name=host)
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mock_hm_get.side_effect = fake_get_host_mapping
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lines = []
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def fake_status(msg):
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lines.append(msg)
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ctxt = context.get_admin_context()
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mappings = host_mapping.discover_hosts(ctxt, cell_uuid=uuids.cell1,
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status_fn=fake_status,
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by_service=True)
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self.assertEqual(1, len(mappings))
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self.assertEqual(['host1'],
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sorted([m.host for m in mappings]))
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expected = """\
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Getting computes from cell: %(cell)s
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Creating host mapping for service host1
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Found 1 unmapped computes in cell: %(cell)s""" % {'cell': uuids.cell1}
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self.assertEqual(expected, '\n'.join(lines))
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@ -1626,6 +1626,15 @@ class CellV2CommandsTestCase(test.NoDBTestCase):
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# Check the return when strict=False
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self.assertIsNone(self.commands.discover_hosts())
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@mock.patch('nova.objects.host_mapping.discover_hosts')
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def test_discover_hosts_by_service(self, mock_discover_hosts):
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mock_discover_hosts.return_value = ['fake']
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ret = self.commands.discover_hosts(by_service=True, strict=True)
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self.assertEqual(0, ret)
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mock_discover_hosts.assert_called_once_with(mock.ANY, None,
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mock.ANY,
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True)
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def test_validate_transport_url_in_conf(self):
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from_conf = 'fake://user:pass@host:port/'
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self.flags(transport_url=from_conf)
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@ -0,0 +1,8 @@
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---
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features:
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- |
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The nova-manage discover_hosts command now has a ``--by-service`` option which
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allows discovering hosts in a cell purely by the presence of a nova-compute
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binary. At this point, there is no need to use this unless you're using ironic,
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as it is less efficient. However, if you are using ironic, this allows discovery
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and mapping of hosts even when no ironic nodes are present.
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