Force InnoDB engine on interfaces table

If the system is set to use MyISAM engine as default, during upgrade
a new conductor_hardware_interfaces table will be created with MyISAM
engine. This will cause a mix of InnoDB and MyISAM tables in single
database, and obsolete a foreign key to conductors table.

This bug in particular fails test_models_sync unit test, when it is
executed on a system, where MyISAM is set as default option for local
MySQL server.

Change-Id: Ic47426b1a12eda5728e9971a27ad3767c0245d50
Closes-Bug: 1702158

ironic/db/sqlalchemy/alembic/versions/2353895ecfae_add_conductor_hardware_interfaces_table.py

@@ -44,4 +44,6 @@ def upgrade():
                     sa.UniqueConstraint(
                         'conductor_id', 'hardware_type',
                         'interface_type', 'interface_name',
-                        name='uniq_conductorhardwareinterfaces0'))
+                        name='uniq_conductorhardwareinterfaces0'),
+                    mysql_charset='utf8',
+                    mysql_engine='InnoDB')

releasenotes/notes/bug-1702158-79bf57bd4d8087b6.yaml

@@ -0,0 +1,22 @@
+---
+fixes:
+  - |
+    Fixes a bug 1702158, where the wrong database engine is used for the
+    conductor_hardware_interfaces table, if the system is using MySQL prior to
+    version 5.5 (or the default_storage_engine option is set explicitly to
+    'MyISAM' in my.cnf). In this case, a table could be created with MyISAM
+    engine and foreign key constraint conductor_id(conductors.id) ignored.
+upgrade:
+  - |
+    Due to a bug 1702158, conductor_hardware_interfaces table could be created
+    with MyISAM database engine, while all other tables in ironic database are
+    using InnoDB engine. This could happen during initial installation, or
+    upgrade to ocata release, if the system is using MySQL prior to version 5.5
+    (or the default_storage_engine option is set explicitly to 'MyISAM' in
+    my.cnf). If this is the case, conductor_hardware_interfaces needs to be
+    manually migrated to InnoDB, and foreign key constraint re-created::
+
+      alter table conductor_hardware_interfaces engine='InnoDB';
+      alter table conductor_hardware_interfaces
+        add constraint conductor_hardware_interfaces_ibfk_1
+        foreign key (conductor_id) references conductors(id);