Add nova-manage ironic-compute-node-move

When people transition from three ironic nova-compute processes down
to one process, we need a way to move the ironic nodes, and any
associcated instances, between nova-compute processes.

For saftey, a nova-compute process must first be forced_down via
the API, similar to when using evacaute, before moving the associated
ironic nodes to another nova-compute process. The destination
nova-compute process should ideally not be running, but not forced
down.

blueprint ironic-shards

Change-Id: I7ef25e27bf8c47f994e28c59858cf3df30975b05

Author: JohnGarbutt

doc/source/cli/nova-manage.rst

@@ -465,6 +465,47 @@ command completed successfully with exit code 0.
    * - 127
      - Invalid input was provided.
 
+db ironic_compute_node_move
+---------------------------
+
+.. program:: nova-manage db ironic_compute_node_move
+
+.. code-block:: shell
+
+    nova-manage db ironic_compute_node_move --ironic-node-uuid <uuid> --destination-host <host>
+
+Move ironic nodes, along with any associated instances,
+between nova-compute services.
+
+This is useful when migrating away from using peer_list and multiple
+hash ring balanced nova-compute servers to the new ironic shard system.
+
+First you must turn off the nova-compute service that currently manages
+the Ironic host. Second you mark that nova-compute service as forced down
+via the Nova API. Third, you ensure the new nova-compute service is
+correctly configured to target the appropriate shard (and optionally
+also a conductor group). Finally, most Ironic nodes should now move to
+the new service, but any Ironic nodes with instances on them
+will need to be manually moved to their new Ironic service
+by using this nova-manage command.
+
+.. versionadded:: 28.0.0 (2023.2 Bobcat)
+
+.. rubric:: Options
+
+.. option:: --ironic-node-uuid <uuid>
+
+    Ironic node uuid to be moved (which is also the Nova compute node uuid
+    and the uuid of corresponding resource provider in Placement).
+
+    The Nova compute service that currently manages this Ironic node
+    must first be marked a "forced down" via the Nova API, in a similar
+    way to a down hypervisor that is about to have its VMs evacuated to
+    a replacement hypervisor.
+
+.. option:: --destination-host <host>
+
+    Destination ironic nova-compute service CONF.host.
 
 API Database Commands
 =====================

nova/cmd/manage.py

@@ -620,6 +620,47 @@ def online_data_migrations(self, max_count=None):
         # "there are more migrations, but not completable right now"
         return ran and 1 or 0
 
+    @args('--ironic-node-uuid', metavar='<uuid>', dest='compute_node_uuid',
+          help='UUID of Ironic node to be moved between services')
+    @args('--destination-host', metavar='<host>',
+          dest='destination_service_host',
+          help='Destination ironic nova-compute service CONF.host')
+    def ironic_compute_node_move(self, compute_node_uuid,
+                                 destination_service_host):
+        ctxt = context.get_admin_context()
+
+        destination_service = objects.Service.get_by_compute_host(
+            ctxt, destination_service_host)
+        if destination_service.forced_down:
+            raise exception.NovaException(
+                "Destination compute is forced down!")
+
+        target_compute_node = objects.ComputeNode.get_by_uuid(
+            ctxt, compute_node_uuid)
+        source_service = objects.Service.get_by_id(
+            ctxt, target_compute_node.service_id)
+        if not source_service.forced_down:
+            raise exception.NovaException(
+                "Source service is not yet forced down!")
+
+        instances = objects.InstanceList.get_by_host_and_node(
+            ctxt, target_compute_node.host,
+            target_compute_node.hypervisor_hostname)
+        if len(instances) > 1:
+            raise exception.NovaException(
+                "Found an ironic host with more than one instance! "
+                "Please delete all Nova instances that do not match "
+                "the instance uuid recorded on the Ironic node.")
+
+        target_compute_node.service_id = destination_service.id
+        target_compute_node.host = destination_service.host
+        target_compute_node.save()
+
+        for instance in instances:
+            # this is a bit like evacuate, except no need to rebuild
+            instance.host = destination_service.host
+            instance.save()
+
 
 class ApiDbCommands(object):
     """Class for managing the api database."""

nova/tests/functional/test_nova_manage.py

@@ -162,7 +162,9 @@ def setUp(self):
                                     user_id=self.context.user_id,
                                     project_id=self.context.project_id,
                                     flavor=flavor,
-                                    node=cn.hypervisor_hostname)
+                                    node=cn.hypervisor_hostname,
+                                    host=cn.host,
+                                    compute_id=cn.id)
             inst.create()
             self.insts.append(inst)
 
@@ -172,6 +174,57 @@ def setUp(self):
                            if i.node == self.cn4.hypervisor_hostname]
 
 
+class TestIronicComputeNodeMove(NovaManageDBIronicTest):
+    """Functional tests for "nova-manage db ironic_compute_node_move" CLI."""
+    api_major_version = 'v2.1'
+
+    def setUp(self):
+        super(TestIronicComputeNodeMove, self).setUp()
+        self.enforce_fk_constraints()
+        self.cli = manage.DbCommands()
+        self.output = StringIO()
+        self.useFixture(fixtures.MonkeyPatch('sys.stdout', self.output))
+
+    def test_ironic_compute_node_move_success(self):
+        self.service1.forced_down = True
+        self.service1.save()
+        self.assertEqual(self.service1.id, self.cn1.service_id)
+        # move cn1 on service1 to service2
+        node_uuid = self.cn1.uuid
+        dest_host = self.service2.host
+
+        self.commands.ironic_compute_node_move(node_uuid, dest_host)
+
+        # check the compute node got moved to service 2
+        updated_cn1 = objects.ComputeNode.get_by_id(self.context, self.cn1.id)
+        self.assertEqual(self.service2.id, updated_cn1.service_id)
+        self.assertEqual(self.service2.host, updated_cn1.host)
+        # check the instance got moved too
+        updated_instance = objects.Instance.get_by_id(
+            self.context, self.insts[0].id)
+        self.assertEqual(self.service2.host, updated_instance.host)
+
+    def test_ironic_compute_node_move_raise_not_forced_down(self):
+        node_uuid = self.cn1.uuid
+        dest_host = self.service2.host
+
+        self.assertRaises(exception.NovaException,
+                          self.commands.ironic_compute_node_move,
+                          node_uuid, dest_host)
+
+    def test_ironic_compute_node_move_raise_forced_down(self):
+        self.service1.forced_down = True
+        self.service1.save()
+        self.service2.forced_down = True
+        self.service2.save()
+        node_uuid = self.cn1.uuid
+        dest_host = self.service2.host
+
+        self.assertRaises(exception.NovaException,
+                          self.commands.ironic_compute_node_move,
+                          node_uuid, dest_host)
+
+
 class NovaManageCellV2Test(test.TestCase):
     def setUp(self):
         super(NovaManageCellV2Test, self).setUp()

releasenotes/notes/ironic-shards-5641e4b1ab5bb7aa.yaml

@@ -10,3 +10,8 @@ features:
     which ironic nodes are managed by each nova-compute service.
     Note that when you use ``[ironic]shard`` the ``[ironic]peer_list``
     is hard coded to a single nova-compute service.
+
+    There is a new nova-manage command ``db ironic_compute_node_move`` that
+    can be used to move ironic nodes, and the associated instances, between
+    nova-compute services. This is useful when migrating from the legacy
+    hash ring based HA towards the new sharding approach.