Always start convergence worker service

The purpose of the cfg.CONF.convergence_engine option is to determine
whether new stacks will be created using convergence or not. For some
reason, however, the worker service was not started when the option was
disabled, meaning that previously-created convergence stacks could no
longer be updated (there was a hack in place to allow them to be deleted).

Always start the worker service and continue operating any existing
convergence stacks in convergence mode, regardless of the current setting
for new stacks.

Change-Id: Ic3574e4d15ac48b2bc8e0e8101c81d24f40f0606
Related-Bug: #1508324

2 files changed, 15 insertions, 14 deletions

diff --git a/heat/engine/service.py b/heat/engine/service.py
index 0101e5e3c..cffcbeffa 100644
--- a/heat/engine/service.py
+++ b/heat/engine/service.py
@@ -345,14 +345,13 @@ class EngineService(service.ServiceBase):
         LOG.debug("Starting listener for engine %s", self.engine_id)
         self.listener.start()
 
-        if cfg.CONF.convergence_engine:
-            self.worker_service = worker.WorkerService(
-                host=self.host,
-                topic=rpc_worker_api.TOPIC,
-                engine_id=self.engine_id,
-                thread_group_mgr=self.thread_group_mgr
-            )
-            self.worker_service.start()
+        self.worker_service = worker.WorkerService(
+            host=self.host,
+            topic=rpc_worker_api.TOPIC,
+            engine_id=self.engine_id,
+            thread_group_mgr=self.thread_group_mgr
+        )
+        self.worker_service.start()
 
         target = messaging.Target(
             version=self.RPC_API_VERSION, server=self.host,
@@ -401,8 +400,7 @@ class EngineService(service.ServiceBase):
         if self.listener:
             self.listener.stop()
 
-        if cfg.CONF.convergence_engine and self.worker_service:
-            # Stop the WorkerService
+        if self.worker_service:
             self.worker_service.stop()
 
         # Wait for all active threads to be finished
@@ -1373,7 +1371,7 @@ class EngineService(service.ServiceBase):
         stack = parser.Stack.load(cnxt, stack=st)
         self.resource_enforcer.enforce_stack(stack, is_registered_policy=True)
 
-        if stack.convergence and cfg.CONF.convergence_engine:
+        if stack.convergence:
             stack.thread_group_mgr = self.thread_group_mgr
             template = templatem.Template.create_empty_template(
                 from_template=stack.t)
diff --git a/heat/tests/engine/service/test_service_engine.py b/heat/tests/engine/service/test_service_engine.py
index a66e8e0de..421c2e359 100644
--- a/heat/tests/engine/service/test_service_engine.py
+++ b/heat/tests/engine/service/test_service_engine.py
@@ -227,6 +227,8 @@ class ServiceEngineTest(common.HeatTestCase):
                 return_value=mock.Mock())
     @mock.patch('heat.engine.service.EngineListener',
                 return_value=mock.Mock())
+    @mock.patch('heat.engine.worker.WorkerService',
+                return_value=mock.Mock())
     @mock.patch('oslo_service.threadgroup.ThreadGroup',
                 return_value=mock.Mock())
     @mock.patch.object(service.EngineService, '_configure_db_conn_pool_size')
@@ -234,16 +236,17 @@ class ServiceEngineTest(common.HeatTestCase):
             self,
             configure_db_conn_pool_size,
             thread_group_class,
+            worker_service_class,
             engine_listener_class,
             thread_group_manager_class,
             sample_uuid_method,
             rpc_client_class,
             target_class,
             rpc_server_method):
-        cfg.CONF.set_default('convergence_engine', False)
+        cfg.CONF.set_override('convergence_engine', False)
         self._test_engine_service_start(
             thread_group_class,
-            None,
+            worker_service_class,
             engine_listener_class,
             thread_group_manager_class,
             sample_uuid_method,
@@ -280,7 +283,7 @@ class ServiceEngineTest(common.HeatTestCase):
             rpc_client_class,
             target_class,
             rpc_server_method):
-        cfg.CONF.set_default('convergence_engine', True)
+        cfg.CONF.set_override('convergence_engine', True)
         self._test_engine_service_start(
             thread_group_class,
             worker_service_class,