Cells: Simple setup/migration command

This provides a single command for users to run if they're setting up
cells on a new deployment, or migrating from non-cells and want a basic
setup. Cell0 is setup on the same db host as the nova_api db.

Change-Id: I73157128a3e24e49438caca1cbb19a9f5b5a7f7e

nova/cmd/manage.py

@@ -1181,6 +1181,21 @@ class CellCommands(object):
 class CellV2Commands(object):
     """Commands for managing cells v2."""
 
+    # TODO(melwitt): Remove this when the oslo.messaging function
+    # for assembling a transport url from ConfigOpts is available
+    @args('--transport-url', metavar='<transport url>', required=True,
+          dest='transport_url',
+          help='The transport url for the cell message queue')
+    def simple_cell_setup(self, transport_url):
+        cell_uuid = self._map_cell_and_hosts(transport_url)
+        if cell_uuid is None:
+            # There are no compute hosts which means no cell_mapping was
+            # created. This should also mean that there are no instances.
+            return 1
+        self.map_cell0()
+        self.map_instances(cell_uuid)
+        return 0
+
     @args('--database_connection',
           metavar='<database_connection>',
           help='The database connection url for cell0. '

nova/tests/unit/test_nova_manage.py

@@ -1088,3 +1088,47 @@ class CellV2CommandsTestCase(test.TestCase):
         self.assertEqual('none:///', cell_mapping.transport_url)
         self.assertEqual('fake://netloc/nova_api_cell0',
                          cell_mapping.database_connection)
+
+    def test_migrate_single_command(self):
+        ctxt = context.RequestContext()
+        CONF.set_default('connection',
+                         'fake://netloc/nova_api',
+                         group='api_database')
+        values = {
+                'vcpus': 4,
+                'memory_mb': 4096,
+                'local_gb': 1024,
+                'vcpus_used': 2,
+                'memory_mb_used': 2048,
+                'local_gb_used': 512,
+                'hypervisor_type': 'Hyper-Dan-VM-ware',
+                'hypervisor_version': 1001,
+                'cpu_info': 'Schmintel i786',
+            }
+        for i in range(3):
+            host = 'host%s' % i
+            compute_node = objects.ComputeNode(ctxt, host=host, **values)
+            compute_node.create()
+
+        transport_url = "fake://guest:devstack@127.0.0.1:9999/"
+        cell_uuid = uuidutils.generate_uuid()
+        with mock.patch.object(uuidutils, 'generate_uuid',
+                return_value=cell_uuid):
+            self.commands.simple_cell_setup(transport_url)
+
+        # Check cell0 from default
+        cell_mapping = objects.CellMapping.get_by_uuid(ctxt,
+                objects.CellMapping.CELL0_UUID)
+        self.assertEqual('cell0', cell_mapping.name)
+        self.assertEqual('none:///', cell_mapping.transport_url)
+        self.assertEqual('fake://netloc/nova_api_cell0',
+                         cell_mapping.database_connection)
+
+        # Verify the cell mapping
+        cell_mapping = objects.CellMapping.get_by_uuid(ctxt, cell_uuid)
+        self.assertEqual(transport_url, cell_mapping.transport_url)
+        # Verify the host mappings
+        for i in range(3):
+            host = 'host%s' % i
+            host_mapping = objects.HostMapping.get_by_host(ctxt, host)
+            self.assertEqual(cell_mapping.uuid, host_mapping.cell_mapping.uuid)

releasenotes/notes/cells-single-migration-command-0e98d66e31e02a50.yaml

@@ -0,0 +1,13 @@
+---
+upgrade:
+  - A new nova-manage command has been added which will upgrade a deployment to
+    cells v2. Running the command will setup a single cell containing the
+    existing hosts and instances. No data or instances will be moved during
+    this operation, but new data will be added to the nova_api database.  New
+    instances booted after this point will be placed into the cell.  Please
+    note that this does not mean that cells v2 is fully functional at this
+    time, but this is a significant part of the effort to get there.
+    The new command is
+    "nova-manage cell_v2 simple_cell_setup --transport_url <transport_url>"
+    where transport_url is the connection information for the current message
+    queue used by Nova.