Use listener pools in designate-sink

configuring pools for notificaiton listeners is an alternative approach
to using per-component notification topics, however not all
oslo.messaging drivers support it (from currently available, zmq and
amqp1 do not, rabbit and kafka do support listener pools).

This patch adds a config option 'listener-pool-name' to [service:sink]
config section (defaults to None) that can be used to configure a common
pool for designate-sink notification listeners if the messaging driver
does support them.

Change-Id: I4fc1c7264671c3102c067beb7298879e62214d60

designate/rpc.py

@@ -198,7 +198,7 @@ def get_server(target, endpoints, serializer=None):
         TRANSPORT, target, dispatcher, 'eventlet')
 
 
-def get_listener(targets, endpoints, serializer=None):
+def get_listener(targets, endpoints, serializer=None, pool=None):
     assert TRANSPORT is not None
     if serializer is None:
         serializer = JsonPayloadSerializer()
@@ -206,6 +206,7 @@ def get_listener(targets, endpoints, serializer=None):
                                                targets,
                                                endpoints,
                                                executor='eventlet',
+                                               pool=pool,
                                                serializer=serializer)
 
 

designate/sink/__init__.py

@@ -26,6 +26,11 @@ OPTS = [
                help='Number of sink greenthreads to spawn'),
     cfg.ListOpt('enabled-notification-handlers', default=[],
                 help='Enabled Notification Handlers'),
+    cfg.StrOpt('listener-pool-name',
+               help='pool name to use for oslo.messaging '
+               'notification listener. '
+               'Note that listener pooling is not supported '
+               'by all oslo.messaging drivers.'),
 ]
 
 

designate/sink/service.py

@@ -68,7 +68,9 @@ class Service(service.Service):
 
         # TODO(ekarlso): Change this is to endpoint objects rather then
         # ourselves?
-        self._server = rpc.get_listener(targets, [self])
+        self._server = rpc.get_listener(
+            targets, [self],
+            pool=cfg.CONF['service:sink'].listener_pool_name)
 
         if len(targets) > 0:
             self._server.start()

releasenotes/notes/pool-listener-6689ffa50345ba6e.yaml

@@ -0,0 +1,15 @@
+---
+features:
+  - |
+    Designate-Sink service now supports notification listener pooling
+    for those oslo.messaging drivers that support this feature
+    (currently those are ``rabbit``/``kombu`` and ``kafka``).
+    `Listener pools <https://docs.openstack.org/oslo.messaging/latest/reference/notification_listener.html>`_
+    is an alternative to specifying several topics for notification consumers
+    in configuration of service that emits notifications.
+
+    To enable listener pooling, set the option
+    ``[service:sink]listener_pool_name`` to some string value, that must be the
+    same for all designate-sink service instances.
+    Default value of this option (``None``) disables notification listener
+    pooling.