From 5fdef82a30bf36fbbe2073163e201fedb4849d1b Mon Sep 17 00:00:00 2001
From: Pavlo Shchelokovskyy <shchelokovskyy@gmail.com>
Date: Tue, 26 Jun 2018 17:38:13 +0300
Subject: [PATCH] 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                                  |  3 ++-
 designate/sink/__init__.py                        |  5 +++++
 designate/sink/service.py                         |  4 +++-
 .../notes/pool-listener-6689ffa50345ba6e.yaml     | 15 +++++++++++++++
 4 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 releasenotes/notes/pool-listener-6689ffa50345ba6e.yaml

diff --git a/designate/rpc.py b/designate/rpc.py
index e1ed5d8ea..8702f442c 100644
--- a/designate/rpc.py
+++ b/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)
 
 
diff --git a/designate/sink/__init__.py b/designate/sink/__init__.py
index adf4c2c51..c6557cfc6 100644
--- a/designate/sink/__init__.py
+++ b/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.'),
 ]
 
 
diff --git a/designate/sink/service.py b/designate/sink/service.py
index d8341c845..90db96db0 100644
--- a/designate/sink/service.py
+++ b/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()
diff --git a/releasenotes/notes/pool-listener-6689ffa50345ba6e.yaml b/releasenotes/notes/pool-listener-6689ffa50345ba6e.yaml
new file mode 100644
index 000000000..56f9216ee
--- /dev/null
+++ b/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.