1 files changed, 108 insertions, 0 deletions
diff --git a/nova/virt/node.py b/nova/virt/node.py
new file mode 100644
index 0000000000..4cb3d0a573
--- /dev/null
+++ b/nova/virt/node.py
@@ -0,0 +1,108 @@
+#    Copyright 2022 Red Hat, inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import logging
+import os
+import uuid
+
+from oslo_utils import uuidutils
+
+import nova.conf
+from nova import exception
+
+CONF = nova.conf.CONF
+LOG = logging.getLogger(__name__)
+COMPUTE_ID_FILE = 'compute_id'
+LOCAL_NODE_UUID = None
+
+
+def write_local_node_uuid(node_uuid):
+    # We only ever write an identity file in the CONF.state_path
+    # location
+    fn = os.path.join(CONF.state_path, COMPUTE_ID_FILE)
+
+    # Try to create the identity file and write our uuid into it. Fail
+    # if the file exists (since it shouldn't if we made it here).
+    try:
+        with open(fn, 'x') as f:
+            f.write(node_uuid)
+    except FileExistsError:
+        # If the file exists, we must either fail or re-survey all the
+        # potential files. If we just read and return it, it could be
+        # inconsistent with files in the other locations.
+        raise exception.InvalidNodeConfiguration(
+            reason='Identity file %s appeared unexpectedly' % fn)
+    except Exception as e:
+        raise exception.InvalidNodeConfiguration(
+            reason='Unable to write uuid to %s: %s' % (fn, e))
+
+    LOG.info('Wrote node identity %s to %s', node_uuid, fn)
+
+
+def read_local_node_uuid():
+    locations = ([os.path.dirname(f) for f in CONF.config_file] +
+                 [CONF.state_path])
+
+    uuids = []
+    found = []
+    for location in locations:
+        fn = os.path.join(location, COMPUTE_ID_FILE)
+        try:
+            # UUIDs should be 36 characters in canonical format. Read
+            # a little more to be graceful about whitespace in/around
+            # the actual value we want to read. However, it must parse
+            # to a legit UUID once we strip the whitespace.
+            with open(fn) as f:
+                content = f.read(40)
+            node_uuid = str(uuid.UUID(content.strip()))
+        except FileNotFoundError:
+            continue
+        except ValueError:
+            raise exception.InvalidNodeConfiguration(
+                reason='Unable to parse UUID from %s' % fn)
+        uuids.append(node_uuid)
+        found.append(fn)
+
+    if uuids:
+        # Any identities we found must be consistent, or we fail
+        first = uuids[0]
+        for i, (node_uuid, fn) in enumerate(zip(uuids, found)):
+            if node_uuid != first:
+                raise exception.InvalidNodeConfiguration(
+                    reason='UUID %s in %s does not match %s' % (
+                        node_uuid, fn, uuids[i - 1]))
+        LOG.info('Determined node identity %s from %s', first, found[0])
+        return first
+    else:
+        return None
+
+
+def get_local_node_uuid():
+    """Read or create local node uuid file.
+
+    :returns: UUID string read from file, or generated
+    """
+    global LOCAL_NODE_UUID
+
+    if LOCAL_NODE_UUID is not None:
+        return LOCAL_NODE_UUID
+
+    node_uuid = read_local_node_uuid()
+    if not node_uuid:
+        node_uuid = uuidutils.generate_uuid()
+        LOG.info('Generated node identity %s', node_uuid)
+        write_local_node_uuid(node_uuid)
+
+    LOCAL_NODE_UUID = node_uuid
+    return node_uuid