Lowercase ironic driver hash ring and ignore case in cache

Recently we had a customer case where attempts to add new ironic nodes
to an existing undercloud resulted in half of the nodes failing to be
detected and added to nova. Ironic API returned all of the newly added
nodes when called by the driver, but half of the nodes were not
returned to the compute manager by the driver.

There was only one nova-compute service managing all of the ironic
nodes of the all-in-one typical undercloud deployment.

After days of investigation and examination of a database dump from the
customer, we noticed that at some point the customer had changed the
hostname of the machine from something containing uppercase letters to
the same name but all lowercase. The nova-compute service record had
the mixed case name and the CONF.host (socket.gethostname()) had the
lowercase name.

The hash ring logic adds all of the nova-compute service hostnames plus
CONF.host to hash ring, then the ironic driver reports only the nodes
it owns by retrieving a service hostname from the ring based on a hash
of each ironic node UUID.

Because of the machine hostname change, the hash ring contained, for
example: {'MachineHostName', 'machinehostname'} when it should have
contained only one hostname. And because the hash ring contained two
hostnames, the driver was able to retrieve only half of the nodes as
nodes that it owned. So half of the new nodes were excluded and not
added as new compute nodes.

This adds lowercasing of hosts that are added to the hash ring and
ignores case when comparing the CONF.host to the hash ring members
to avoid unnecessary pain and confusion for users that make hostname
changes that are otherwise functionally harmless.

This also adds logging of the set of hash ring members at level DEBUG
to help enable easier debugging of hash ring related situations.

Closes-Bug: #1866380

Change-Id: I617fd59de327de05a198f12b75a381f21945afb0
(cherry picked from commit 7145100ee4)
(cherry picked from commit 588b0484bf)

nova/tests/unit/virt/ironic/test_driver.py

@@ -3308,17 +3308,28 @@ class HashRingTestCase(test.NoDBTestCase):
         self.assertEqual(SENTINEL, self.driver.hash_ring)
         self.mock_is_up.assert_has_calls(is_up_calls)
 
+    def test__refresh_hash_ring_same_host_different_case(self):
+        # Test that we treat Host1 and host1 as the same host
+        # CONF.host is set to 'host1' in __test_refresh_hash_ring
+        services = ['Host1']
+        expected_hosts = {'host1'}
+        self.mock_is_up.return_value = True
+        self._test__refresh_hash_ring(services, expected_hosts)
+
     def test__refresh_hash_ring_one_compute(self):
         services = ['host1']
         expected_hosts = {'host1'}
         self.mock_is_up.return_value = True
         self._test__refresh_hash_ring(services, expected_hosts)
 
-    def test__refresh_hash_ring_many_computes(self):
+    @mock.patch('nova.virt.ironic.driver.LOG.debug')
+    def test__refresh_hash_ring_many_computes(self, mock_log_debug):
         services = ['host1', 'host2', 'host3']
         expected_hosts = {'host1', 'host2', 'host3'}
         self.mock_is_up.return_value = True
         self._test__refresh_hash_ring(services, expected_hosts)
+        expected_msg = 'Hash ring members are %s'
+        mock_log_debug.assert_called_once_with(expected_msg, set(services))
 
     def test__refresh_hash_ring_one_compute_new_compute(self):
         services = []
@@ -3443,6 +3454,26 @@ class NodeCacheTestCase(test.NoDBTestCase):
                                            limit=0, **kwargs)
         self.assertIsNotNone(self.driver.node_cache_time)
 
+    def test__refresh_cache_same_host_different_case(self):
+        # Test that we treat Host1 and host1 as the same host
+        self.host = 'Host1'
+        self.flags(host=self.host)
+        instances = []
+        nodes = [
+            _get_cached_node(
+                uuid=uuidutils.generate_uuid(), instance_uuid=None),
+            _get_cached_node(
+                uuid=uuidutils.generate_uuid(), instance_uuid=None),
+            _get_cached_node(
+                uuid=uuidutils.generate_uuid(), instance_uuid=None),
+        ]
+        hosts = ['host1', 'host1', 'host1']
+
+        self._test__refresh_cache(instances, nodes, hosts)
+
+        expected_cache = {n.uuid: n for n in nodes}
+        self.assertEqual(expected_cache, self.driver.node_cache)
+
     def test__refresh_cache(self):
         # normal operation, one compute service
         instances = []

nova/virt/ironic/driver.py

@@ -724,14 +724,15 @@ class IronicDriver(virt_driver.ComputeDriver):
             if peer_list is None or svc.host in peer_list:
                 is_up = self.servicegroup_api.service_is_up(svc)
                 if is_up:
-                    services.add(svc.host)
+                    services.add(svc.host.lower())
         # NOTE(jroll): always make sure this service is in the list, because
         # only services that have something registered in the compute_nodes
         # table will be here so far, and we might be brand new.
-        services.add(CONF.host)
+        services.add(CONF.host.lower())
 
         self.hash_ring = hash_ring.HashRing(services,
                                             partitions=_HASH_RING_PARTITIONS)
+        LOG.debug('Hash ring members are %s', services)
 
     def _refresh_cache(self):
         # NOTE(lucasagomes): limit == 0 is an indicator to continue
@@ -777,7 +778,7 @@ class IronicDriver(virt_driver.ComputeDriver):
             # nova while the service was down, and not yet reaped, will not be
             # reported until the periodic task cleans it up.
             elif (node.instance_uuid is None and
-                  CONF.host in
+                  CONF.host.lower() in
                   self.hash_ring.get_nodes(node.uuid.encode('utf-8'))):
                 node_cache[node.uuid] = node