conf: Remove '[conductor] topic' opt

This should have been removed in '6ef30d5', but was missed as it used a
different name to the other opts.

Change-Id: I85cb86e0c203967da544750a9e52b207f707e8e5

nova/cmd/conductor.py

@@ -20,6 +20,7 @@ from oslo_concurrency import processutils
 from oslo_log import log as logging
 from oslo_reports import guru_meditation_report as gmr
 
+from nova.conductor import rpcapi
 import nova.conf
 from nova import config
 from nova import objects
@@ -40,7 +41,7 @@ def main():
     gmr.TextGuruMeditation.setup_autorun(version)
 
     server = service.Service.create(binary='nova-conductor',
-                                    topic=CONF.conductor.topic)
+                                    topic=rpcapi.RPC_TOPIC)
     workers = CONF.conductor.workers or processutils.get_worker_count()
     service.serve(server, workers=workers)
     service.wait()

nova/conductor/api.py

@@ -31,7 +31,7 @@ class API(object):
 
     def __init__(self):
         self.conductor_rpcapi = rpcapi.ConductorAPI()
-        self.base_rpcapi = baserpc.BaseAPI(topic=CONF.conductor.topic)
+        self.base_rpcapi = baserpc.BaseAPI(topic=rpcapi.RPC_TOPIC)
 
     def object_backport_versions(self, context, objinst, object_versions):
         return self.conductor_rpcapi.object_backport_versions(context, objinst,

nova/conductor/rpcapi.py

@@ -25,6 +25,7 @@ from nova import profiler
 from nova import rpc
 
 CONF = nova.conf.CONF
+RPC_TOPIC = 'conductor'
 
 
 @profiler.trace_cls("rpc")
@@ -211,7 +212,7 @@ class ConductorAPI(object):
 
     def __init__(self):
         super(ConductorAPI, self).__init__()
-        target = messaging.Target(topic=CONF.conductor.topic, version='3.0')
+        target = messaging.Target(topic=RPC_TOPIC, version='3.0')
         version_cap = self.VERSION_ALIASES.get(CONF.upgrade_levels.conductor,
                                                CONF.upgrade_levels.conductor)
         serializer = objects_base.NovaObjectSerializer()
@@ -278,7 +279,7 @@ class ComputeTaskAPI(object):
 
     def __init__(self):
         super(ComputeTaskAPI, self).__init__()
-        target = messaging.Target(topic=CONF.conductor.topic,
+        target = messaging.Target(topic=RPC_TOPIC,
                                   namespace='compute_task',
                                   version='1.0')
         serializer = objects_base.NovaObjectSerializer()

nova/conf/conductor.py

@@ -26,19 +26,6 @@ and finally, how many worker processes will be used.
 )
 
 ALL_OPTS = [
-    cfg.StrOpt(
-        'topic',
-        default='conductor',
-        deprecated_for_removal=True,
-        deprecated_since='15.0.0',
-        deprecated_reason="""
-There is no need to let users choose the RPC topic for all services - there
-is little gain from this. Furthermore, it makes it really easy to break Nova
-by using this option.
-""",
-        help="""
-Topic exchange name on which conductor nodes listen.
-"""),
     cfg.IntOpt(
         'workers',
         help="""

releasenotes/notes/remove-topic-config-opts-705ebd829a6e80b6.yaml

@@ -0,0 +1,7 @@
+---
+upgrade:
+  - |
+    The ``[conductor] topic`` configuration option was previously deprecated
+    and is now removed from nova.  There was no need to let users choose the
+    RPC topics for all services. There was little benefit from this and it made
+    it really easy to break nova by changing the value of topic options.