Make the event streamer transport URL configurable

This adds a way to configure the event streamer transport URL
so it can post to a different queue, e.g. Neutron's

Change-Id: I69d3d6d30e33878052f2c56b8c79a14cc4ec1b24

etc/octavia.conf

@@ -245,6 +245,14 @@
 # Topic for octavia's events sent to a queue
 # event_stream_topic = neutron_lbaas_event
 
+# Transport URL to use for the neutron-lbaas synchronization event stream
+# when neutron and octavia have separate queues.
+# For Single Host, specify one full transport URL:
+#   event_stream_transport_url = rabbit://<user>:<pass>@127.0.0.1:5672/<vhost>
+# For HA, specify queue nodes in cluster, comma delimited:
+#   event_stream_transport_url = rabbit://<user>:<pass>@server01,<user>:<pass>@server02/<vhost>
+# event_stream_transport_url =
+
 [house_keeping]
 # Interval in seconds to initiate spare amphora checks
 # spare_check_interval = 30

octavia/common/config.py

@@ -195,6 +195,10 @@ oslo_messaging_opts = [
     cfg.StrOpt('event_stream_topic',
                default='neutron_lbaas_event',
                help=_('topic name for communicating events through a queue')),
+    cfg.StrOpt('event_stream_transport_url', default=None,
+               help=_('Transport URL to use for the neutron-lbaas'
+                      'synchronization event stream when neutron and octavia'
+                      'have separate queues.')),
 ]
 
 haproxy_amphora_opts = [

octavia/controller/queue/event_queue.py

@@ -60,7 +60,12 @@ class EventStreamerNeutron(EventStreamerBase):
 
     def __init__(self):
         topic = cfg.CONF.oslo_messaging.event_stream_topic
-        self.transport = oslo_messaging.get_rpc_transport(cfg.CONF)
+        if cfg.CONF.oslo_messaging.event_stream_transport_url:
+            # Use custom URL
+            self.transport = oslo_messaging.get_rpc_transport(
+                cfg.CONF, cfg.CONF.oslo_messaging.event_stream_transport_url)
+        else:
+            self.transport = oslo_messaging.get_rpc_transport(cfg.CONF)
         self.target = oslo_messaging.Target(topic=topic, exchange="common",
                                             namespace='control', fanout=False,
                                             version='1.0')

releasenotes/notes/custom_eventstreamer_queue_url-7a98bd6a7e92e9de.yaml

@@ -0,0 +1,16 @@
+---
+features:
+  - |
+    In some enviornments (e.g. OSA) Neutron and Octavia use different queues
+    (at least different vhosts) and so if Octavia posts to the Octavia queue
+    and Neutron listens on the Neutron queue the events will never make it
+    over.
+
+    This adds a way to configure a custom queue for the event streamer thus
+    allowing to post messages to the Neutron queue if needed.
+security:
+  - |
+    Depending on how the other queue is set up additional passwords for the
+    other queue will be in the Octavia config file. Operators should take care
+    of setting up appropriate users with appropriate restrictions to the
+    topic(s) needed.