concurrency: Deprecate 'TpoolDbapiWrapper'

This has been marked as experimented since before oslo.db was split out
of nova. We've no test coverage and no idea of whether it even works
nowadays. It's time to plan for its eventual removal.

Change-Id: Ib7a5a6e1124c44a742b003442f815022a866bcbb
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

oslo_db/concurrency.py

@@ -17,23 +17,40 @@ import copy
 import logging
 import threading
 
+from debtcollector import removals
 from oslo_config import cfg
 
 from oslo_db import api
 
-
 LOG = logging.getLogger(__name__)
 
 tpool_opts = [
-    cfg.BoolOpt('use_tpool',
-                default=False,
-                deprecated_name='dbapi_use_tpool',
-                deprecated_group='DEFAULT',
-                help='Enable the experimental use of thread pooling for '
-                     'all DB API calls'),
+    cfg.BoolOpt(
+        'use_tpool',
+        default=False,
+        deprecated_name='dbapi_use_tpool',
+        deprecated_group='DEFAULT',
+        deprecated_for_removal=True,
+        deprecated_since='10.0.0',
+        deprecated_reason=(
+            'This feature has never graduated from experimental status and is '
+            'now being removed due to lack of maintenance and test coverage'
+        ),
+        help=(
+            'Enable the experimental use of thread pooling for '
+            'all DB API calls'
+        ),
+    ),
 ]
 
+_removed_msg = (
+    'Thread pool support in oslo_db is deprecated; you should use '
+    'oslo_db.api.DBAPI.from_config directly'
+)
 
+
+@removals.removed_class(
+    'TpoolDbapiWrapper', message=_removed_msg, version='10.0.0')
 class TpoolDbapiWrapper(object):
     """DB API wrapper class.
 

releasenotes/notes/deprecate-TpoolDbapiWrapper-2ce78aa7cbb9e585.yaml

@@ -0,0 +1,9 @@
+---
+deprecations:
+  - |
+    The ``oslo_db.concurrency.TpoolDbapiWrapper`` class and supporting
+    ``[database] use_tpool`` config option are now deprecated.
+    This feature never graduated from experimental status and is slated for
+    removal due to lack of maintenance and test coverage. Users should switch
+    to ``oslo_db.api.DBAPI.from_config`` and remove references to the
+    deprecated config option from their documentation.