Generate version_id upon add_node

The version_id isn't set during add_node() call. This function is called
when introspection starts for both "new" and existing node_info records.
As a result, race conditions can appear in an HA inspector deployment (see
the refered bug).

This patch makes sure a version_id is generated during the add_node() call
so stale record updates can be detected through the version_id mismatch
between the inspector memory and the DB record.

Change-Id: I422473e888e5e49abb3e598fc2cf2f330620bdcd
Closes-Bug: #1719627

ironic_inspector/node_cache.py

@@ -686,9 +686,12 @@ def add_node(uuid, state, **attributes):
     started_at = timeutils.utcnow()
     with db.ensure_transaction() as session:
         _delete_node(uuid)
-        db.Node(uuid=uuid, state=state, started_at=started_at).save(session)
+        version_id = uuidutils.generate_uuid()
+        db.Node(uuid=uuid, state=state, version_id=version_id,
+                started_at=started_at).save(session)
 
         node_info = NodeInfo(uuid=uuid, state=state, started_at=started_at,
+                             version_id=version_id,
                              ironic=attributes.pop('ironic', None))
         for (name, value) in attributes.items():
             if not value:

releasenotes/notes/add_node-with-version_id-24f51e5888480aa0.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    A ``version_id`` is now explicitly generated during the
+    ``node_cache.start_introspection/.add_node`` call to avoid race conditions
+    such as in case of the `two concurrent introspection calls bug`_.
+
+    .. _two concurrent introspection calls bug: https://bugs.launchpad.net/ironic-inspector/+bug/1719627