Enable mutable config in Watcher

New releases of oslo.config support a 'mutable' parameter to Opts.
Configuration options are mutable if their oslo.config Opt's
mutable=True is set. This mutable setting is respected when the oslo
method mutate_config_files is called instead of reload_config_files.
Icec3e664f3fe72614e373b2938e8dee53cf8bc5e allows services to tell
oslo.service they want mutate_config_files to be called by specifying
the 'restart_method=mutate' parameter, what this patch does.

The default mutable configuration options (set by oslo.config Opts'
mutable=True) are:
- [DEFAULT]/pin_release_version
- [DEFAULT]/debug
- [DEFAULT]/log_config_append

Concrete params, that made mutable in Watcher:

* watcher_decision_engine.action_plan_expiry
* watcher_decision_engine.check_periodic_interval
* watcher_decision_engine.continuous_audit_interval
* gnocchi_client.query_max_retries
* gnocchi_client.query_timeout
* DEFAULT.periodic_interval

Change-Id: If28f2de094d99471a3ab756c947e29ae3d8a28a2
Implements: bp mutable-config

watcher/common/service.py

@@ -289,7 +289,7 @@ class Service(service.ServiceBase):
         return api_manager_version
 
 
-def launch(conf, service_, workers=1, restart_method='reload'):
+def launch(conf, service_, workers=1, restart_method='mutate'):
     return service.launch(conf, service_, workers, restart_method)
 
 

watcher/conf/decision_engine.py

@@ -44,18 +44,21 @@ WATCHER_DECISION_ENGINE_OPTS = [
                     'execute strategies'),
     cfg.IntOpt('action_plan_expiry',
                default=24,
+               mutable=True,
                help='An expiry timespan(hours). Watcher invalidates any '
                     'action plan for which its creation time '
                     '-whose number of hours has been offset by this value-'
                     ' is older that the current time.'),
     cfg.IntOpt('check_periodic_interval',
                default=30 * 60,
+               mutable=True,
                help='Interval (in seconds) for checking action plan expiry.')
 ]
 
 WATCHER_CONTINUOUS_OPTS = [
     cfg.IntOpt('continuous_audit_interval',
                default=10,
+               mutable=True,
                help='Interval (in seconds) for checking newly created '
                     'continuous audits.')
 ]

watcher/conf/gnocchi_client.py

@@ -32,9 +32,11 @@ GNOCCHI_CLIENT_OPTS = [
                     'The default is public.'),
     cfg.IntOpt('query_max_retries',
                default=10,
+               mutable=True,
                help='How many times Watcher is trying to query again'),
     cfg.IntOpt('query_timeout',
                default=1,
+               mutable=True,
                help='How many seconds Watcher should wait to do query again')]
 
 

watcher/conf/service.py

@@ -25,6 +25,7 @@ from watcher._i18n import _
 SERVICE_OPTS = [
     cfg.IntOpt('periodic_interval',
                default=60,
+               mutable=True,
                help=_('Seconds between running periodic tasks.')),
     cfg.HostAddressOpt('host',
                        default=socket.gethostname(),