replace WorkerSupportServiceMixin with neutron-lib's WorkerBase

neutron-lib contains the WorkerBase class [1] that is the equivalent of
neutron's WorkerSupportServiceMixin. This patch switches over to
neutron-lib's version.

Note: IIUC no consumers are using WorkerSupportServiceMixin so this
patch can land without waiting for them to sync-up. I've included
the lib impact tag just in case.

NeutronLibImpact

[1] https://review.openstack.org/#/c/424151/
[2] http://codesearch.openstack.org/?q=WorkerSupportServiceMixin

Change-Id: Iacf1b6dfe318e3e6cfc76e61c65d407cf9ae7b36

neutron/db/l3_db.py

@@ -27,6 +27,7 @@ from neutron_lib import constants
 from neutron_lib import context as n_ctx
 from neutron_lib import exceptions as n_exc
 from neutron_lib.plugins import directory
+from neutron_lib.services import base as base_services
 from oslo_log import log as logging
 from oslo_utils import uuidutils
 import six
@@ -70,7 +71,7 @@ CORE_ROUTER_ATTRS = ('id', 'name', 'tenant_id', 'admin_state_up', 'status')
 
 @registry.has_registry_receivers
 class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
-                          neutron_worker.WorkerSupportServiceMixin,
+                          base_services.WorkerBase,
                           st_attr.StandardAttrDescriptionMixin):
     """Mixin class to add L3/NAT router methods to db_base_plugin_v2."""
 

neutron/neutron_plugin_base_v2.py

@@ -22,13 +22,12 @@ methods that needs to be implemented by a v2 Neutron Plug-in.
 
 import abc
 
+from neutron_lib.services import base as base_services
 import six
 
-from neutron import worker as neutron_worker
-
 
 @six.add_metaclass(abc.ABCMeta)
-class NeutronPluginBaseV2(neutron_worker.WorkerSupportServiceMixin):
+class NeutronPluginBaseV2(base_services.WorkerBase):
 
     @abc.abstractmethod
     def create_subnet(self, context, subnet):

neutron/worker.py

@@ -14,39 +14,6 @@ from neutron_lib import worker
 from oslo_service import loopingcall
 
 
-class WorkerSupportServiceMixin(object):
-
-    @property
-    def _workers(self):
-        try:
-            return self.__workers
-        except AttributeError:
-            self.__workers = []
-        return self.__workers
-
-    def get_workers(self):
-        """Returns a collection neutron_lib.worker.BaseWorker instances
-        needed by this service
-        """
-        return list(self._workers)
-
-    def add_worker(self, worker):
-        """Adds neutron_lib.worker.BaseWorker needed for this service
-
-        If a object needs to define workers thread/processes outside of API/RPC
-        workers then it will call this method to register worker. Should be
-        called on initialization stage before running services
-        """
-        self._workers.append(worker)
-
-    def add_workers(self, workers):
-        """Adds neutron_lib.worker.BaseWorker list needed for this service
-
-        The same as add_worker but adds a list of workers
-        """
-        self._workers.extend(workers)
-
-
 class PeriodicWorker(worker.BaseWorker):
     """A worker that runs a function at a fixed interval."""