Deprecate idle_timeout in api_database

In oslo.db, the 'idle_timeout' has been renamed to
'connection_recycle_time' in
I5e39d5ac81eaa8d85b1dfb18862fe27695ab8b96.

So the 'idle_timeout' in 'api_database' group is
renamed to 'connection_recycle_time' as well.

Change-Id: Ie6e003be241d071904a99fdf6d83bc1186602f99
Closes-Bug: #1716786

nova/conf/database.py

@@ -63,8 +63,9 @@ api_db_opts = [
     cfg.StrOpt('mysql_sql_mode',
                default='TRADITIONAL',
                help=''),
-    cfg.IntOpt('idle_timeout',
+    cfg.IntOpt('connection_recycle_time',
                default=3600,
+               deprecated_name='idle_timeout',
                help=''),
     # TODO(markus_z): We should probably default this to 5 to not rely on the
     # SQLAlchemy default. Otherwise we wouldn't provide a stable default.

nova/db/sqlalchemy/api.py

@@ -87,7 +87,7 @@ def _get_db_conf(conf_group, connection=None):
         __autocommit=True,
         expire_on_commit=False,
         mysql_sql_mode=conf_group.mysql_sql_mode,
-        idle_timeout=conf_group.idle_timeout,
+        connection_recycle_time=conf_group.connection_recycle_time,
         connection_debug=conf_group.connection_debug,
         max_pool_size=conf_group.max_pool_size,
         max_overflow=conf_group.max_overflow,

releasenotes/notes/bug-1716786-7c3fc081f29f4dac.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    The ``idle_timeout`` option in the ``api_database`` group
+    has been renamed to ``connection_recycle_time``.