Display the reply queue's name in timeout logs

It would be helpful if "Timed out waiting for <service>" log messages at least
specified on which `reply_q` it was waited for.

Example without the reply_q:

```
12228 2020-09-14 14:56:37.187 7 WARNING nova.conductor.api
[req-1e081db6-808b-4af1-afc1-b87db7839394 - - - - -] Timed out waiting for
nova-conductor.  Is it running? Or did this service start before
nova-conductor?  Reattempting establishment of nova-conductor connection...:
oslo_messaging.exceptions.MessagingTimeout: Timed out waiting for a reply to
message ID 1640e7ef6f314451ba9a75d9ff6136ad
```

Example after adding the reply_q:

```
12228 2020-09-14 14:56:37.187 7 WARNING nova.conductor.api
[req-1e081db6-808b-4af1-afc1-b87db7839394 - - - - -] Timed out waiting for
nova-conductor.  Is it running? Or did this service start before
nova-conductor?  Reattempting establishment of nova-conductor connection...:
oslo_messaging.exceptions.MessagingTimeout: Timed out waiting for a reply
(reply_2882766a63b540dabaf7d019cf0c0cda)
to message ID 1640e7ef6f314451ba9a75d9ff6136ad
```

It could help us to more merely debug and observe if something went
wrong with a reply queue.

Change-Id: Ied2c881c71930dc631919113adc00112648f9d72
Closes-Bug: #1896925

oslo_messaging/_drivers/amqpdriver.py

@@ -583,9 +583,11 @@ class ReplyWaiter(object):
         self.waiters.remove(msg_id)
 
     @staticmethod
-    def _raise_timeout_exception(msg_id):
+    def _raise_timeout_exception(msg_id, reply_q):
         raise oslo_messaging.MessagingTimeout(
-            'Timed out waiting for a reply to message ID %s.', msg_id)
+            'Timed out waiting for a reply %(reply_q)s '
+            'to message ID %(msg_id)s.',
+            {'msg_id': msg_id, 'reply_q': reply_q})
 
     def _process_reply(self, data):
         self.msg_id_cache.check_duplicate_message(data)
@@ -599,7 +601,7 @@ class ReplyWaiter(object):
         ending = data.get('ending', False)
         return result, ending
 
-    def wait(self, msg_id, timeout, call_monitor_timeout):
+    def wait(self, msg_id, timeout, call_monitor_timeout, reply_q):
         # NOTE(sileht): for each msg_id we receive two amqp message
         # first one with the payload, a second one to ensure the other
         # have finish to send the payload
@@ -617,16 +619,26 @@ class ReplyWaiter(object):
         final_reply = None
         ending = False
         while not ending:
-            timeout = timer.check_return(self._raise_timeout_exception, msg_id)
+            timeout = timer.check_return(
+                self._raise_timeout_exception,
+                msg_id,
+                reply_q
+            )
             if call_monitor_timer and timeout > 0:
                 cm_timeout = call_monitor_timer.check_return(
-                    self._raise_timeout_exception, msg_id)
+                    self._raise_timeout_exception,
+                    msg_id,
+                    reply_q
+                )
                 if cm_timeout < timeout:
                     timeout = cm_timeout
             try:
                 message = self.waiters.get(msg_id, timeout=timeout)
             except queue.Empty:
-                self._raise_timeout_exception(msg_id)
+                self._raise_timeout_exception(
+                    msg_id,
+                    reply_q
+                )
 
             reply, ending = self._process_reply(message)
             if reply is not None:
@@ -700,6 +712,7 @@ class AMQPDriverBase(base.BaseDriver):
               envelope=True, notify=False, retry=None, transport_options=None):
 
         msg = message
+        reply_q = None
         if 'method' in msg:
             LOG.debug('Calling RPC method %s on target %s', msg.get('method'),
                       target.topic)
@@ -707,13 +720,13 @@ class AMQPDriverBase(base.BaseDriver):
             LOG.debug('Sending message to topic %s', target.topic)
 
         if wait_for_reply:
-            _reply_q = self._get_reply_q()
+            reply_q = self._get_reply_q()
             msg_id = uuid.uuid4().hex
             msg.update({'_msg_id': msg_id})
-            msg.update({'_reply_q': _reply_q})
+            msg.update({'_reply_q': reply_q})
             msg.update({'_timeout': call_monitor_timeout})
             LOG.info('Expecting reply to msg %s in queue %s', msg_id,
-                     _reply_q)
+                     reply_q)
 
         rpc_amqp._add_unique_id(msg)
         unique_id = msg[rpc_amqp.UNIQUE_ID]
@@ -756,7 +769,7 @@ class AMQPDriverBase(base.BaseDriver):
 
             if wait_for_reply:
                 result = self._waiter.wait(msg_id, timeout,
-                                           call_monitor_timeout)
+                                           call_monitor_timeout, reply_q)
                 if isinstance(result, Exception):
                     raise result
                 return result

oslo_messaging/tests/drivers/test_impl_rabbit.py

@@ -668,7 +668,7 @@ class TestRacyWaitForReply(test_utils.BaseTestCase):
         wait_conditions = []
         orig_reply_waiter = amqpdriver.ReplyWaiter.wait
 
-        def reply_waiter(self, msg_id, timeout, call_monitor_timeout):
+        def reply_waiter(self, msg_id, timeout, call_monitor_timeout, reply_q):
             if wait_conditions:
                 cond = wait_conditions.pop()
                 with cond:
@@ -676,7 +676,7 @@ class TestRacyWaitForReply(test_utils.BaseTestCase):
                 with cond:
                     cond.wait()
             return orig_reply_waiter(self, msg_id, timeout,
-                                     call_monitor_timeout)
+                                     call_monitor_timeout, reply_q)
 
         self.useFixture(fixtures.MockPatchObject(
             amqpdriver.ReplyWaiter, 'wait', reply_waiter))

releasenotes/notes/reply_q-timeout-e3c3bae636e8bc74.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    The name of the ``reply_q`` is now logged when a timeout occurs while waiting for a reply.