Remove locks before RPC bus is started

A partner performing some testing recognized a case where if a request
is sent to the Ironic Conductor while it is in the process of starting,
and the request makes it into be processed, yet latter the operation
fails with errors such as NodeNotLocked exception. Notably they were
able to reproduce this by requesting the attachment or detachment of
a VIF at the same time as restarting the conductor.

In part, this condition is due to to the conductor being restarted
where the conductors table includes the node being restarted and
the webserver has not possibly had a chance to observe that the
conductor is in the process of restarting as the hash ring is
still valid.

In short - Incoming RPC requests can come in during the initialization
window and as such we should not remove locks while the conductor could
possibly already be receiving work.

As such, we've added a ``prepare_host`` method which initializes
the conductor database connection and removes the stale locks.
Under normal operating conditions, the database client is reused.

rhbz# 1847305

Change-Id: I8e759168f1dc81cdcf430f3e33be990731595ec3

6 files changed, 54 insertions, 6 deletions

diff --git a/ironic/common/rpc_service.py b/ironic/common/rpc_service.py
index 9df03b917..a38582250 100644
--- a/ironic/common/rpc_service.py
+++ b/ironic/common/rpc_service.py
@@ -48,6 +48,8 @@ class RPCService(service.Service):
         admin_context = context.get_admin_context()
 
         serializer = objects_base.IronicObjectSerializer(is_server=True)
+        # Perform preparatory actions before starting the RPC listener
+        self.manager.prepare_host()
         if CONF.rpc_transport == 'json-rpc':
             self.rpcserver = json_rpc.WSGIService(self.manager,
                                                   serializer)
diff --git a/ironic/conductor/base_manager.py b/ironic/conductor/base_manager.py
index cd63d875c..d4361dfa9 100644
--- a/ironic/conductor/base_manager.py
+++ b/ironic/conductor/base_manager.py
@@ -80,6 +80,33 @@ class BaseConductorManager(object):
         self._started = False
         self._shutdown = None
         self._zeroconf = None
+        self.dbapi = None
+
+    def prepare_host(self):
+        """Prepares host for initialization
+
+        Removes existing database entries involved with node locking for nodes
+        in a transitory power state and nodes that are presently locked by
+        the hostname of this conductor.
+
+        Under normal operation, this is also when the initial database
+        connectivity is established for the conductor's normal operation.
+        """
+        # NOTE(TheJulia) We need to clear locks early on in the process
+        # of starting where the database shows we still hold them.
+        # This must be done before we re-register our existence in the
+        # conductors table and begin accepting new requests via RPC as
+        # if we do not then we may squash our *new* locks from new work.
+
+        if not self.dbapi:
+            LOG.debug('Initializing database client for %s.', self.host)
+            self.dbapi = dbapi.get_instance()
+        LOG.debug('Removing stale locks from the database matching '
+                  'this conductor\'s hostname: %s', self.host)
+        # clear all target_power_state with locks by this conductor
+        self.dbapi.clear_node_target_power_state(self.host)
+        # clear all locks held by this conductor before registering
+        self.dbapi.clear_node_reservations_for_conductor(self.host)
 
     def init_host(self, admin_context=None):
         """Initialize the conductor host.
@@ -97,7 +124,8 @@ class BaseConductorManager(object):
                                  'conductor manager'))
         self._shutdown = False
 
-        self.dbapi = dbapi.get_instance()
+        if not self.dbapi:
+            self.dbapi = dbapi.get_instance()
 
         self._keepalive_evt = threading.Event()
         """Event for the keepalive thread."""
@@ -141,10 +169,6 @@ class BaseConductorManager(object):
 
         self._collect_periodic_tasks(admin_context)
 
-        # clear all target_power_state with locks by this conductor
-        self.dbapi.clear_node_target_power_state(self.host)
-        # clear all locks held by this conductor before registering
-        self.dbapi.clear_node_reservations_for_conductor(self.host)
         try:
             # Register this conductor with the cluster
             self.conductor = objects.Conductor.register(
diff --git a/ironic/tests/unit/common/test_rpc_service.py b/ironic/tests/unit/common/test_rpc_service.py
index ec440324c..f187ff7e0 100644
--- a/ironic/tests/unit/common/test_rpc_service.py
+++ b/ironic/tests/unit/common/test_rpc_service.py
@@ -36,13 +36,14 @@ class TestRPCService(base.TestCase):
         mgr_class = "ConductorManager"
         self.rpc_svc = rpc_service.RPCService(host, mgr_module, mgr_class)
 
+    @mock.patch.object(manager.ConductorManager, 'prepare_host', autospec=True)
     @mock.patch.object(oslo_messaging, 'Target', autospec=True)
     @mock.patch.object(objects_base, 'IronicObjectSerializer', autospec=True)
     @mock.patch.object(rpc, 'get_server', autospec=True)
     @mock.patch.object(manager.ConductorManager, 'init_host', autospec=True)
     @mock.patch.object(context, 'get_admin_context', autospec=True)
     def test_start(self, mock_ctx, mock_init_method,
-                   mock_rpc, mock_ios, mock_target):
+                   mock_rpc, mock_ios, mock_target, mock_prepare_method):
         mock_rpc.return_value.start = mock.MagicMock()
         self.rpc_svc.handle_signal = mock.MagicMock()
         self.rpc_svc.start()
@@ -50,5 +51,6 @@ class TestRPCService(base.TestCase):
         mock_target.assert_called_once_with(topic=self.rpc_svc.topic,
                                             server="fake_host")
         mock_ios.assert_called_once_with(is_server=True)
+        mock_prepare_method.assert_called_once_with(self.rpc_svc.manager)
         mock_init_method.assert_called_once_with(self.rpc_svc.manager,
                                                  mock_ctx.return_value)
diff --git a/ironic/tests/unit/conductor/mgr_utils.py b/ironic/tests/unit/conductor/mgr_utils.py
index e5bc43bcb..9baadaf42 100644
--- a/ironic/tests/unit/conductor/mgr_utils.py
+++ b/ironic/tests/unit/conductor/mgr_utils.py
@@ -143,6 +143,7 @@ class ServiceSetUpMixin(object):
             self.service.init_host()
         else:
             with mock.patch.object(periodics, 'PeriodicWorker', autospec=True):
+                self.service.prepare_host()
                 self.service.init_host()
         self.addCleanup(self._stop_service)
 
diff --git a/ironic/tests/unit/conductor/test_base_manager.py b/ironic/tests/unit/conductor/test_base_manager.py
index 35d8146ed..7680af153 100644
--- a/ironic/tests/unit/conductor/test_base_manager.py
+++ b/ironic/tests/unit/conductor/test_base_manager.py
@@ -31,6 +31,7 @@ from ironic.conductor import base_manager
 from ironic.conductor import manager
 from ironic.conductor import notification_utils
 from ironic.conductor import task_manager
+from ironic.db import api as dbapi
 from ironic.drivers import fake_hardware
 from ironic.drivers import generic
 from ironic.drivers.modules import deploy_utils
@@ -300,6 +301,15 @@ class StartStopTestCase(mgr_utils.ServiceSetUpMixin, db_base.DbTestCase):
         mock_zc.close.assert_called_once_with()
         self.assertIsNone(self.service._zeroconf)
 
+    @mock.patch.object(dbapi, 'get_instance', autospec=True)
+    def test_start_dbapi_single_call(self, mock_dbapi):
+        self._start_service()
+        # NOTE(TheJulia): This seems like it should only be 1, but
+        # the hash ring initailization pulls it's own database connection
+        # instance, which is likely a good thing, thus this is 2 instead of
+        # 3 without reuse of the database connection.
+        self.assertEqual(2, mock_dbapi.call_count)
+
 
 class CheckInterfacesTestCase(mgr_utils.ServiceSetUpMixin, db_base.DbTestCase):
     def test__check_enabled_interfaces_success(self):
diff --git a/releasenotes/notes/remove-locks-first-d12ac27106f800f8.yaml b/releasenotes/notes/remove-locks-first-d12ac27106f800f8.yaml
new file mode 100644
index 000000000..a7e0cb958
--- /dev/null
+++ b/releasenotes/notes/remove-locks-first-d12ac27106f800f8.yaml
@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    Fixes an issue where ``ironic-conductor`` initialization could return a
+    ``NodeNotLocked`` error for requests requiring locks when the conductor
+    was starting. This was due to the conductor removing locks after
+    beginning accepting new work. The lock removal has been moved to after
+    the Database connectivity has been established but before the RPC bus
+    is initialized.