Add the mandatory flag for direct send

With this feature, the server will raise and log a Message Undeliverable
exception. So it is possible to log immediately an error in case the
reply queue does not exist for some reason.

This is part of blueprint transport-options
The blueprint link is [1]
Please follow the link [2] to use and test the feature.

1-
https://blueprints.launchpad.net/oslo.messaging/+spec/transport-options
2- https://github.com/Gsantomaggio/rabbitmq-utils/
tree/master/openstack/mandatory_test

Change-Id: Iac7474c06ef425a2afe5bcd912e51510ba1c8fb3

oslo_messaging/_drivers/impl_rabbit.py

@@ -168,6 +168,12 @@ rabbit_opts = [
                default=2,
                help='How often times during the heartbeat_timeout_threshold '
                'we check the heartbeat.'),
+    cfg.IntOpt('direct_mandatory_flag',
+               default=True,
+               help='Enable/Disable the RabbitMQ mandatory flag '
+               'for direct send. The direct send is used as reply,'
+               'so the MessageUndeliverable exception is raised'
+               ' in case the client queue does not exist.'),
 ]
 
 LOG = logging.getLogger(__name__)
@@ -492,6 +498,7 @@ class Connection(object):
             # if it was already monkey patched by eventlet/greenlet.
             global threading
             threading = stdlib_threading
+        self.direct_mandatory_flag = driver_conf.direct_mandatory_flag
 
         if self.ssl:
             self.ssl_version = driver_conf.ssl_version
@@ -1291,9 +1298,11 @@ class Connection(object):
                                          durable=False,
                                          auto_delete=True,
                                          passive=True)
-
+        options = oslo_messaging.TransportOptions(
+            at_least_once=self.direct_mandatory_flag)
         self._ensure_publishing(self._publish_and_raises_on_missing_exchange,
-                                exchange, msg, routing_key=msg_id)
+                                exchange, msg, routing_key=msg_id,
+                                transport_options=options)
 
     def topic_send(self, exchange_name, topic, msg, timeout=None, retry=None,
                    transport_options=None):

oslo_messaging/rpc/server.py

@@ -1,4 +1,3 @@
-
 # Copyright 2013 Red Hat, Inc.
 #
 #    Licensed under the Apache License, Version 2.0 (the "License"); you may
@@ -124,6 +123,7 @@ A simple example of an RPC server with multiple endpoints might be::
 import logging
 import sys
 
+from oslo_messaging import exceptions
 from oslo_messaging.rpc import dispatcher as rpc_dispatcher
 from oslo_messaging import server as msg_server
 from oslo_messaging import transport as msg_transport
@@ -178,13 +178,19 @@ class RPCServer(msg_server.MessageHandlingServer):
                 message.reply(res)
             else:
                 message.reply(failure=failure)
+        except exceptions.MessageUndeliverable as e:
+            LOG.exception(
+                "MessageUndeliverable error, "
+                "source exception: %s, routing_key: %s, exchange: %s: ",
+                e.exception, e.routing_key, e.exchange
+            )
         except Exception:
             LOG.exception("Can not send reply for message")
         finally:
-                # NOTE(dhellmann): Remove circular object reference
-                # between the current stack frame and the traceback in
-                # exc_info.
-                del failure
+            # NOTE(dhellmann): Remove circular object reference
+            # between the current stack frame and the traceback in
+            # exc_info.
+            del failure
 
 
 def get_rpc_server(transport, target, endpoints,
@@ -222,6 +228,7 @@ def expected_exceptions(*exceptions):
     ExpectedException, which is used internally by the RPC sever. The RPC
     client will see the original exception type.
     """
+
     def outer(func):
         def inner(*args, **kwargs):
             try:
@@ -234,7 +241,9 @@ def expected_exceptions(*exceptions):
             # ignored and thrown as normal.
             except exceptions:
                 raise rpc_dispatcher.ExpectedException()
+
         return inner
+
     return outer