Deprecate service-to-driver mapping for backups

This mapping was introduced for backward compatibility in 2013 and
works only for Swift and Ceph. I don't think that somebody actually uses
such old way to configure backup service so if should be safe to
deprecate it.

Change-Id: Ifc5642d11edfaf200df00ae640f18c65451853ae

cinder/backup/manager.py

@@ -34,6 +34,7 @@ Volume backups can be created, restored, deleted and listed.
 import os
 from oslo_config import cfg
 from oslo_log import log as logging
+from oslo_log import versionutils
 import oslo_messaging as messaging
 from oslo_service import loopingcall
 from oslo_service import periodic_task
@@ -106,6 +107,11 @@ class BackupManager(manager.ThreadPoolManager):
         """Maps services to drivers."""
 
         if service in mapper:
+            msg = ("Using legacy backup service configuration like "
+                   "cinder.backup.services.* is deprecated and "
+                   "will be removed in the 'R' release. Please use "
+                   "the cinder.backup.drivers.* method instead.")
+            versionutils.report_deprecated_feature(LOG, msg)
             return mapper[service]
         return service
 

releasenotes/notes/deprecate-backup-service-to-driver-mapping-a3afabd4f55eca01.yaml

@@ -0,0 +1,8 @@
+---
+deprecations:
+  - |
+    Backup service to driver mapping is deprecated. If you use old values
+    like 'cinder.backup.services.swift' or 'cinder.backup.services.ceph'
+    it should be changed to 'cinder.backup.drivers.swift' or
+    'cinder.backup.drivers.ceph' accordingly to get your backup service
+    working in the 'R' release.