diff --git a/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_base.py b/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_base.py
index 3c232e365..6b8a70bd9 100644
--- a/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_base.py
+++ b/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_base.py
@@ -12,11 +12,9 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import abc
 from concurrent import futures
 import logging
 
-import oslo_messaging
 from oslo_messaging._drivers import common as rpc_common
 from oslo_messaging._drivers.zmq_driver.client.publishers \
     import zmq_publisher_base
@@ -41,27 +39,17 @@ class DealerPublisherBase(zmq_publisher_base.PublisherBase):
         super(DealerPublisherBase, self).__init__(sockets_manager, sender,
                                                   receiver)
 
-    @staticmethod
-    def _check_pattern(request, supported_pattern):
-        if request.msg_type != supported_pattern:
-            raise zmq_publisher_base.UnsupportedSendPattern(
-                zmq_names.message_type_str(request.msg_type)
-            )
+    def _check_received_data(self, reply_id, reply, request):
+        assert isinstance(reply, zmq_response.Reply), "Reply expected!"
 
-    @staticmethod
-    def _raise_timeout(request):
-        raise oslo_messaging.MessagingTimeout(
-            "Timeout %(tout)s seconds was reached for message %(msg_id)s" %
-            {"tout": request.timeout, "msg_id": request.message_id}
-        )
-
-    def _recv_reply(self, request):
+    def _recv_reply(self, request, socket):
+        self.receiver.register_socket(socket)
         reply_future = \
             self.receiver.track_request(request)[zmq_names.REPLY_TYPE]
 
         try:
-            _, reply = reply_future.result(timeout=request.timeout)
-            assert isinstance(reply, zmq_response.Reply), "Reply expected!"
+            reply_id, reply = reply_future.result(timeout=request.timeout)
+            self._check_received_data(reply_id, reply, request)
         except AssertionError:
             LOG.error(_LE("Message format error in reply for %s"),
                       request.message_id)
@@ -77,30 +65,3 @@ class DealerPublisherBase(zmq_publisher_base.PublisherBase):
             )
         else:
             return reply.reply_body
-
-    def send_call(self, request):
-        self._check_pattern(request, zmq_names.CALL_TYPE)
-
-        socket = self.connect_socket(request)
-        if not socket:
-            self._raise_timeout(request)
-
-        self.sender.send(socket, request)
-        self.receiver.register_socket(socket)
-        return self._recv_reply(request)
-
-    @abc.abstractmethod
-    def _send_non_blocking(self, request):
-        pass
-
-    def send_cast(self, request):
-        self._check_pattern(request, zmq_names.CAST_TYPE)
-        self._send_non_blocking(request)
-
-    def send_fanout(self, request):
-        self._check_pattern(request, zmq_names.CAST_FANOUT_TYPE)
-        self._send_non_blocking(request)
-
-    def send_notify(self, request):
-        self._check_pattern(request, zmq_names.NOTIFY_TYPE)
-        self._send_non_blocking(request)
diff --git a/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_direct.py b/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_direct.py
index f6d30401c..9356ac623 100644
--- a/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_direct.py
+++ b/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_direct.py
@@ -40,19 +40,19 @@ class DealerPublisherDirect(zmq_dealer_publisher_base.DealerPublisherBase):
         super(DealerPublisherDirect, self).__init__(conf, matchmaker, sender,
                                                     receiver)
 
-    def connect_socket(self, request):
+    def _connect_socket(self, request):
         try:
             return self.sockets_manager.get_socket(request.target)
         except retrying.RetryError:
             return None
 
-    def _send_non_blocking(self, request):
-        socket = self.connect_socket(request)
+    def _send_request(self, request):
+        socket = self._connect_socket(request)
         if not socket:
-            return
-
+            return None
         if request.msg_type in zmq_names.MULTISEND_TYPES:
             for _ in range(socket.connections_count()):
                 self.sender.send(socket, request)
         else:
             self.sender.send(socket, request)
+        return socket
diff --git a/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_proxy.py b/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_proxy.py
index 1c29e5d7f..dce8c2ff0 100644
--- a/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_proxy.py
+++ b/oslo_messaging/_drivers/zmq_driver/client/publishers/dealer/zmq_dealer_publisher_proxy.py
@@ -55,15 +55,11 @@ class DealerPublisherProxy(zmq_dealer_publisher_base.DealerPublisherBase):
         return six.b(self.conf.oslo_messaging_zmq.rpc_zmq_host + "/" +
                      str(uuid.uuid4()))
 
-    def connect_socket(self, request):
-        return self.socket
-
-    def send_call(self, request):
-        request.routing_key = \
-            self.routing_table.get_routable_host(request.target)
-        if request.routing_key is None:
-            self._raise_timeout(request)
-        return super(DealerPublisherProxy, self).send_call(request)
+    def _check_received_data(self, reply_id, reply, request):
+        super(DealerPublisherProxy, self)._check_received_data(reply_id, reply,
+                                                               request)
+        assert reply_id == request.routing_key, \
+            "Reply from recipient expected!"
 
     def _get_routing_keys(self, request):
         if request.msg_type in zmq_names.DIRECT_TYPES:
@@ -74,16 +70,20 @@ class DealerPublisherProxy(zmq_dealer_publisher_base.DealerPublisherBase):
                 if self.conf.oslo_messaging_zmq.use_pub_sub else \
                 self.routing_table.get_all_hosts(request.target)
 
-    def _send_non_blocking(self, request):
-        for routing_key in self._get_routing_keys(request):
-            if routing_key is None:
-                LOG.warning(_LW("Matchmaker contains no record for specified "
-                                "target %(target)s. Dropping message %(id)s.")
-                            % {"target": request.target,
-                               "id": request.message_id})
-                continue
+    def _send_request(self, request):
+        routing_keys = [routing_key
+                        for routing_key in self._get_routing_keys(request)
+                        if routing_key is not None]
+        if not routing_keys:
+            LOG.warning(_LW("Matchmaker contains no records for specified "
+                            "target %(target)s. Dropping message %(msg_id)s.")
+                        % {"target": request.target,
+                           "msg_id": request.message_id})
+            return None
+        for routing_key in routing_keys:
             request.routing_key = routing_key
             self.sender.send(self.socket, request)
+        return self.socket
 
     def cleanup(self):
         super(DealerPublisherProxy, self).cleanup()
diff --git a/oslo_messaging/_drivers/zmq_driver/client/publishers/zmq_publisher_base.py b/oslo_messaging/_drivers/zmq_driver/client/publishers/zmq_publisher_base.py
index 8c6c100ed..c7c4cc8d4 100644
--- a/oslo_messaging/_drivers/zmq_driver/client/publishers/zmq_publisher_base.py
+++ b/oslo_messaging/_drivers/zmq_driver/client/publishers/zmq_publisher_base.py
@@ -17,8 +17,10 @@ import logging
 
 import six
 
+import oslo_messaging
 from oslo_messaging._drivers import common as rpc_common
 from oslo_messaging._drivers.zmq_driver import zmq_async
+from oslo_messaging._drivers.zmq_driver import zmq_names
 from oslo_messaging._i18n import _LE
 
 LOG = logging.getLogger(__name__)
@@ -72,27 +74,48 @@ class PublisherBase(object):
         self.sender = sender
         self.receiver = receiver
 
+    @staticmethod
+    def _check_message_pattern(expected, actual):
+        if expected != actual:
+            raise UnsupportedSendPattern(zmq_names.message_type_str(actual))
+
+    @staticmethod
+    def _raise_timeout(request):
+        raise oslo_messaging.MessagingTimeout(
+            "Timeout %(tout)s seconds was reached for message %(msg_id)s" %
+            {"tout": request.timeout, "msg_id": request.message_id}
+        )
+
     @abc.abstractmethod
-    def connect_socket(self, request):
-        """Get connected socket ready for sending given request
-        or None otherwise (i.e. if connection can't be established).
+    def _send_request(self, request):
+        """Send the request and return a socket used for that.
+        Return value of None means some failure (e.g. connection
+        can't be established, etc).
         """
 
     @abc.abstractmethod
+    def _recv_reply(self, request, socket):
+        """Wait for a reply via the socket used for sending the request."""
+
     def send_call(self, request):
-        pass
+        self._check_message_pattern(zmq_names.CALL_TYPE, request.msg_type)
+        socket = self._send_request(request)
+        if not socket:
+            raise self._raise_timeout(request)
+        return self._recv_reply(request, socket)
 
-    @abc.abstractmethod
     def send_cast(self, request):
-        pass
+        self._check_message_pattern(zmq_names.CAST_TYPE, request.msg_type)
+        self._send_request(request)
 
-    @abc.abstractmethod
     def send_fanout(self, request):
-        pass
+        self._check_message_pattern(zmq_names.CAST_FANOUT_TYPE,
+                                    request.msg_type)
+        self._send_request(request)
 
-    @abc.abstractmethod
     def send_notify(self, request):
-        pass
+        self._check_message_pattern(zmq_names.NOTIFY_TYPE, request.msg_type)
+        self._send_request(request)
 
     def cleanup(self):
         """Cleanup publisher. Close allocated connections."""
diff --git a/oslo_messaging/_drivers/zmq_driver/client/zmq_ack_manager.py b/oslo_messaging/_drivers/zmq_driver/client/zmq_ack_manager.py
index 01bbc35a9..e1d9e8897 100644
--- a/oslo_messaging/_drivers/zmq_driver/client/zmq_ack_manager.py
+++ b/oslo_messaging/_drivers/zmq_driver/client/zmq_ack_manager.py
@@ -61,9 +61,11 @@ class AckManagerProxy(AckManagerBase):
         )
 
     def _wait_for_ack(self, ack_future):
-        request, socket = ack_future.args
+        request = ack_future.request
         retries = \
             request.retry or self.conf.oslo_messaging_zmq.rpc_retry_attempts
+        if retries is None:
+            retries = -1
         timeout = self.conf.oslo_messaging_zmq.rpc_ack_timeout_base
 
         done = False
@@ -72,8 +74,9 @@ class AckManagerProxy(AckManagerBase):
                 reply_id, response = ack_future.result(timeout=timeout)
                 done = True
                 assert response is None, "Ack expected!"
-                assert reply_id == request.routing_key, \
-                    "Ack from recipient expected!"
+                if reply_id is not None:
+                    assert reply_id == request.routing_key, \
+                        "Ack from recipient expected!"
             except AssertionError:
                 LOG.error(_LE("Message format error in ack for %s"),
                           request.message_id)
@@ -82,10 +85,10 @@ class AckManagerProxy(AckManagerBase):
                                 "for %(msg_id)s"),
                             {"tout": timeout,
                              "msg_id": request.message_id})
-                if retries is None or retries != 0:
-                    if retries is not None and retries > 0:
+                if retries != 0:
+                    if retries > 0:
                         retries -= 1
-                    self.sender.send(socket, request)
+                    self.sender.send(ack_future.socket, request)
                     timeout *= \
                         self.conf.oslo_messaging_zmq.rpc_ack_timeout_multiplier
                 else:
@@ -93,18 +96,35 @@ class AckManagerProxy(AckManagerBase):
                                 request.message_id)
                     done = True
 
-        self.receiver.untrack_request(request)
+        if request.msg_type != zmq_names.CALL_TYPE:
+            self.receiver.untrack_request(request)
 
-    def _get_ack_future(self, request):
-        socket = self.publisher.connect_socket(request)
+    def _send_request_and_get_ack_future(self, request):
+        socket = self.publisher._send_request(request)
+        if not socket:
+            return None
         self.receiver.register_socket(socket)
         ack_future = self.receiver.track_request(request)[zmq_names.ACK_TYPE]
-        ack_future.args = request, socket
+        ack_future.request = request
+        ack_future.socket = socket
         return ack_future
 
+    def send_call(self, request):
+        ack_future = self._send_request_and_get_ack_future(request)
+        if not ack_future:
+            self.publisher._raise_timeout(request)
+        self._pool.submit(self._wait_for_ack, ack_future)
+        try:
+            return self.publisher._recv_reply(request, ack_future.socket)
+        finally:
+            if not ack_future.done():
+                ack_future.set_result((None, None))
+
     def send_cast(self, request):
-        self.publisher.send_cast(request)
-        self._pool.submit(self._wait_for_ack, self._get_ack_future(request))
+        ack_future = self._send_request_and_get_ack_future(request)
+        if not ack_future:
+            return
+        self._pool.submit(self._wait_for_ack, ack_future)
 
     def cleanup(self):
         self._pool.shutdown(wait=True)
diff --git a/oslo_messaging/_drivers/zmq_driver/client/zmq_receivers.py b/oslo_messaging/_drivers/zmq_driver/client/zmq_receivers.py
index 9f7aeecf7..40c824e53 100644
--- a/oslo_messaging/_drivers/zmq_driver/client/zmq_receivers.py
+++ b/oslo_messaging/_drivers/zmq_driver/client/zmq_receivers.py
@@ -63,9 +63,12 @@ class ReceiverBase(object):
         a dict of futures for monitoring all types of responses.
         """
         futures = {}
+        message_id = request.message_id
         for message_type in self.message_types:
-            future = futurist.Future()
-            self._set_future(request.message_id, message_type, future)
+            future = self._get_future(message_id, message_type)
+            if future is None:
+                future = futurist.Future()
+                self._set_future(message_id, message_type, future)
             futures[message_type] = future
         return futures
 
@@ -92,7 +95,8 @@ class ReceiverBase(object):
 
     def _run_loop(self):
         data, socket = self._poller.poll(
-            timeout=self.conf.oslo_messaging_zmq.rpc_poll_timeout)
+            timeout=self.conf.oslo_messaging_zmq.rpc_poll_timeout
+        )
         if data is None:
             return
         reply_id, message_type, message_id, response = data
diff --git a/oslo_messaging/_drivers/zmq_driver/client/zmq_routing_table.py b/oslo_messaging/_drivers/zmq_driver/client/zmq_routing_table.py
index d6f9b94ee..569826dd1 100644
--- a/oslo_messaging/_drivers/zmq_driver/client/zmq_routing_table.py
+++ b/oslo_messaging/_drivers/zmq_driver/client/zmq_routing_table.py
@@ -76,9 +76,9 @@ class RoutingTable(object):
         key = str(target)
         if key not in self.routing_table:
             try:
-                self.routing_table[key] = (get_hosts_retry(
-                    target, zmq_names.socket_type_str(zmq.DEALER)),
-                    time.time())
+                hosts = get_hosts_retry(
+                    target, zmq_names.socket_type_str(zmq.DEALER))
+                self.routing_table[key] = (hosts, time.time())
             except retrying.RetryError:
                 LOG.warning(_LW("Matchmaker contains no hosts for target %s")
                             % key)
diff --git a/oslo_messaging/_drivers/zmq_driver/matchmaker/zmq_matchmaker_redis.py b/oslo_messaging/_drivers/zmq_driver/matchmaker/zmq_matchmaker_redis.py
index ff2036800..22ad912fc 100644
--- a/oslo_messaging/_drivers/zmq_driver/matchmaker/zmq_matchmaker_redis.py
+++ b/oslo_messaging/_drivers/zmq_driver/matchmaker/zmq_matchmaker_redis.py
@@ -239,8 +239,6 @@ class MatchmakerRedis(zmq_matchmaker_base.MatchmakerBase):
 
     @redis_connection_warn
     def get_hosts_fanout(self, target, listener_type):
-        LOG.debug("[Redis] get_hosts for target %s", target)
-
         hosts = []
 
         if target.topic and target.server:
@@ -250,18 +248,19 @@ class MatchmakerRedis(zmq_matchmaker_base.MatchmakerBase):
         key = zmq_address.prefix_str(target.topic, listener_type)
         hosts.extend(self._get_hosts_by_key(key))
 
+        LOG.debug("[Redis] get_hosts_fanout for target %(target)s: %(hosts)s",
+                  {"target": target, "hosts": hosts})
+
         return hosts
 
     def get_hosts_fanout_retry(self, target, listener_type):
         return self._retry_method(target, listener_type, self.get_hosts_fanout)
 
     def _retry_method(self, target, listener_type, method):
-        conf = self.conf
-
         @retry(retry_on_result=retry_if_empty,
                wrap_exception=True,
-               wait_fixed=conf.matchmaker_redis.wait_timeout,
-               stop_max_delay=conf.matchmaker_redis.check_timeout)
+               wait_fixed=self.conf.matchmaker_redis.wait_timeout,
+               stop_max_delay=self.conf.matchmaker_redis.check_timeout)
         def _get_hosts_retry(target, listener_type):
             return method(target, listener_type)
         return _get_hosts_retry(target, listener_type)
diff --git a/oslo_messaging/_drivers/zmq_driver/server/consumers/zmq_dealer_consumer.py b/oslo_messaging/_drivers/zmq_driver/server/consumers/zmq_dealer_consumer.py
index 3e3e1107d..0ec03ceb3 100644
--- a/oslo_messaging/_drivers/zmq_driver/server/consumers/zmq_dealer_consumer.py
+++ b/oslo_messaging/_drivers/zmq_driver/server/consumers/zmq_dealer_consumer.py
@@ -40,7 +40,7 @@ class DealerConsumer(zmq_consumer_base.SingleSocketConsumer):
     def __init__(self, conf, poller, server):
         self.ack_sender = zmq_senders.AckSenderProxy(conf)
         self.reply_sender = zmq_senders.ReplySenderProxy(conf)
-        self.received_messages = zmq_ttl_cache.TTLCache(
+        self.messages_cache = zmq_ttl_cache.TTLCache(
             ttl=conf.oslo_messaging_zmq.rpc_message_ttl
         )
         self.sockets_manager = zmq_sockets_manager.SocketsManager(
@@ -92,11 +92,11 @@ class DealerConsumer(zmq_consumer_base.SingleSocketConsumer):
 
                 message = zmq_incoming_message.ZmqIncomingMessage(
                     context, message, reply_id, message_id, socket,
-                    ack_sender, reply_sender
+                    ack_sender, reply_sender, self.messages_cache
                 )
 
-                # drop duplicate message
-                if message_id in self.received_messages:
+                # drop a duplicate message
+                if message_id in self.messages_cache:
                     LOG.warning(
                         _LW("[%(host)s] Dropping duplicate %(msg_type)s "
                             "message %(msg_id)s"),
@@ -104,10 +104,16 @@ class DealerConsumer(zmq_consumer_base.SingleSocketConsumer):
                          "msg_type": zmq_names.message_type_str(msg_type),
                          "msg_id": message_id}
                     )
+                    # NOTE(gdavoian): send yet another ack for the non-CALL
+                    # message, since the old one might be lost;
+                    # for the CALL message also try to resend its reply
+                    # (of course, if it was already obtained and cached).
                     message.acknowledge()
+                    if msg_type == zmq_names.CALL_TYPE:
+                        message.reply_from_cache()
                     return None
 
-                self.received_messages.add(message_id)
+                self.messages_cache.add(message_id)
                 LOG.debug(
                     "[%(host)s] Received %(msg_type)s message %(msg_id)s",
                     {"host": self.host,
@@ -124,7 +130,7 @@ class DealerConsumer(zmq_consumer_base.SingleSocketConsumer):
 
     def cleanup(self):
         LOG.info(_LI("[%s] Destroy DEALER consumer"), self.host)
-        self.received_messages.cleanup()
+        self.messages_cache.cleanup()
         self.connection_updater.cleanup()
         super(DealerConsumer, self).cleanup()
 
diff --git a/oslo_messaging/_drivers/zmq_driver/server/zmq_incoming_message.py b/oslo_messaging/_drivers/zmq_driver/server/zmq_incoming_message.py
index d6ab57328..493e50940 100644
--- a/oslo_messaging/_drivers/zmq_driver/server/zmq_incoming_message.py
+++ b/oslo_messaging/_drivers/zmq_driver/server/zmq_incoming_message.py
@@ -25,9 +25,14 @@ zmq = zmq_async.import_zmq()
 
 
 class ZmqIncomingMessage(base.RpcIncomingMessage):
+    """Base class for RPC-messages via ZMQ-driver.
+    Each message may send either acks/replies or just nothing
+    (if acks are disabled and replies are not supported).
+    """
 
     def __init__(self, context, message, reply_id=None, message_id=None,
-                 socket=None, ack_sender=None, reply_sender=None):
+                 socket=None, ack_sender=None, reply_sender=None,
+                 replies_cache=None):
 
         if ack_sender is not None or reply_sender is not None:
             assert socket is not None, "Valid socket expected!"
@@ -41,6 +46,7 @@ class ZmqIncomingMessage(base.RpcIncomingMessage):
         self.socket = socket
         self.ack_sender = ack_sender
         self.reply_sender = reply_sender
+        self.replies_cache = replies_cache
 
     def acknowledge(self):
         if self.ack_sender is not None:
@@ -57,6 +63,14 @@ class ZmqIncomingMessage(base.RpcIncomingMessage):
                                        reply_body=reply,
                                        failure=failure)
             self.reply_sender.send(self.socket, reply)
+            if self.replies_cache is not None:
+                self.replies_cache.add(self.message_id, reply)
+
+    def reply_from_cache(self):
+        if self.reply_sender is not None and self.replies_cache is not None:
+            reply = self.replies_cache.get(self.message_id)
+            if reply is not None:
+                self.reply_sender.send(self.socket, reply)
 
     def requeue(self):
         """Requeue is not supported"""
diff --git a/oslo_messaging/_drivers/zmq_driver/server/zmq_ttl_cache.py b/oslo_messaging/_drivers/zmq_driver/server/zmq_ttl_cache.py
index 963d2d912..49edfbc37 100644
--- a/oslo_messaging/_drivers/zmq_driver/server/zmq_ttl_cache.py
+++ b/oslo_messaging/_drivers/zmq_driver/server/zmq_ttl_cache.py
@@ -24,9 +24,11 @@ zmq = zmq_async.import_zmq()
 
 class TTLCache(object):
 
+    _UNDEFINED = object()
+
     def __init__(self, ttl=None):
         self._lock = threading.Lock()
-        self._expiration_times = {}
+        self._cache = {}
         self._executor = None
 
         if not (ttl is None or isinstance(ttl, (int, float))):
@@ -47,30 +49,31 @@ class TTLCache(object):
     def _is_expired(expiration_time, current_time):
         return expiration_time <= current_time
 
-    def add(self, item):
+    def add(self, key, value=None):
         with self._lock:
-            self._expiration_times[item] = time.time() + self._ttl
+            expiration_time = time.time() + self._ttl
+            self._cache[key] = (value, expiration_time)
 
-    def discard(self, item):
+    def get(self, key, default=None):
         with self._lock:
-            self._expiration_times.pop(item, None)
-
-    def __contains__(self, item):
-        with self._lock:
-            expiration_time = self._expiration_times.get(item)
-            if expiration_time is None:
-                return False
+            data = self._cache.get(key)
+            if data is None:
+                return default
+            value, expiration_time = data
             if self._is_expired(expiration_time, time.time()):
-                self._expiration_times.pop(item)
-                return False
-            return True
+                del self._cache[key]
+                return default
+            return value
+
+    def __contains__(self, key):
+        return self.get(key, self._UNDEFINED) is not self._UNDEFINED
 
     def _update_cache(self):
         with self._lock:
             current_time = time.time()
-            self._expiration_times = \
-                {item: expiration_time for
-                 item, expiration_time in six.iteritems(self._expiration_times)
+            self._cache = \
+                {key: (value, expiration_time) for
+                 key, (value, expiration_time) in six.iteritems(self._cache)
                  if not self._is_expired(expiration_time, current_time)}
         time.sleep(self._ttl)
 
diff --git a/oslo_messaging/_drivers/zmq_driver/zmq_options.py b/oslo_messaging/_drivers/zmq_driver/zmq_options.py
index d59c9b0cd..f7150b156 100644
--- a/oslo_messaging/_drivers/zmq_driver/zmq_options.py
+++ b/oslo_messaging/_drivers/zmq_driver/zmq_options.py
@@ -117,10 +117,8 @@ zmq_opts = [
                      'True means not keeping a queue when server side '
                      'disconnects. False means to keep queue and messages '
                      'even if server is disconnected, when the server '
-                     'appears we send all accumulated messages to it.')
-]
+                     'appears we send all accumulated messages to it.'),
 
-zmq_ack_retry_opts = [
     cfg.IntOpt('rpc_thread_pool_size', default=100,
                help='Maximum number of (green) threads to work concurrently.'),
 
@@ -133,7 +131,7 @@ zmq_ack_retry_opts = [
                 help='Wait for message acknowledgements from receivers. '
                      'This mechanism works only via proxy without PUB/SUB.'),
 
-    cfg.IntOpt('rpc_ack_timeout_base', default=10,
+    cfg.IntOpt('rpc_ack_timeout_base', default=15,
                help='Number of seconds to wait for an ack from a cast/call. '
                     'After each retry attempt this timeout is multiplied by '
                     'some specified multiplier.'),
@@ -155,6 +153,5 @@ def register_opts(conf):
     opt_group = cfg.OptGroup(name='oslo_messaging_zmq',
                              title='ZeroMQ driver options')
     conf.register_opts(zmq_opts, group=opt_group)
-    conf.register_opts(zmq_ack_retry_opts, group=opt_group)
     conf.register_opts(server._pool_opts)
     conf.register_opts(base.base_opts)
diff --git a/oslo_messaging/tests/drivers/zmq/test_zmq_ack_manager.py b/oslo_messaging/tests/drivers/zmq/test_zmq_ack_manager.py
index 05a230198..744b9ba2b 100644
--- a/oslo_messaging/tests/drivers/zmq/test_zmq_ack_manager.py
+++ b/oslo_messaging/tests/drivers/zmq/test_zmq_ack_manager.py
@@ -43,7 +43,7 @@ class TestZmqAckManager(test_utils.BaseTestCase):
                   'use_router_proxy': True,
                   'rpc_thread_pool_size': 1,
                   'rpc_use_acks': True,
-                  'rpc_ack_timeout_base': 3,
+                  'rpc_ack_timeout_base': 5,
                   'rpc_ack_timeout_multiplier': 1,
                   'rpc_retry_attempts': 2}
         self.config(group='oslo_messaging_zmq', **kwargs)
@@ -104,8 +104,8 @@ class TestZmqAckManager(test_utils.BaseTestCase):
         result = self.driver.send(
             self.target, {}, self.message, wait_for_reply=False
         )
-        self.ack_manager._pool.shutdown(wait=True)
         self.assertIsNone(result)
+        self.ack_manager._pool.shutdown(wait=True)
         self.assertTrue(self.listener._received.isSet())
         self.assertEqual(self.message, self.listener.message.message)
         self.assertEqual(1, self.send.call_count)
@@ -119,21 +119,20 @@ class TestZmqAckManager(test_utils.BaseTestCase):
             result = self.driver.send(
                 self.target, {}, self.message, wait_for_reply=False
             )
-            self.listener._received.wait(3)
             self.assertIsNone(result)
+            self.listener._received.wait(5)
             self.assertTrue(self.listener._received.isSet())
             self.assertEqual(self.message, self.listener.message.message)
             self.assertEqual(1, self.send.call_count)
             self.assertEqual(1, lost_ack_mock.call_count)
             self.assertEqual(0, self.set_result.call_count)
+            self.listener._received.clear()
         with mock.patch.object(
             zmq_incoming_message.ZmqIncomingMessage, 'acknowledge',
             side_effect=zmq_incoming_message.ZmqIncomingMessage.acknowledge,
             autospec=True
         ) as received_ack_mock:
-            self.listener._received.clear()
             self.ack_manager._pool.shutdown(wait=True)
-            self.listener._received.wait(3)
             self.assertFalse(self.listener._received.isSet())
             self.assertEqual(2, self.send.call_count)
             self.assertEqual(1, received_ack_mock.call_count)
@@ -146,15 +145,15 @@ class TestZmqAckManager(test_utils.BaseTestCase):
             result = self.driver.send(
                 self.target, {}, self.message, wait_for_reply=False
             )
-            self.listener._received.wait(3)
             self.assertIsNone(result)
+            self.listener._received.wait(5)
             self.assertTrue(self.listener._received.isSet())
             self.assertEqual(self.message, self.listener.message.message)
             self.assertEqual(1, self.send.call_count)
             self.assertEqual(1, lost_ack_mock.call_count)
             self.assertEqual(0, self.set_result.call_count)
             self.listener._received.clear()
-            self.listener._received.wait(4.5)
+            self.listener._received.wait(7.5)
             self.assertFalse(self.listener._received.isSet())
             self.assertEqual(2, self.send.call_count)
             self.assertEqual(2, lost_ack_mock.call_count)
@@ -176,10 +175,53 @@ class TestZmqAckManager(test_utils.BaseTestCase):
         result = self.driver.send(
             self.target, {}, self.message, wait_for_reply=False
         )
-        self.ack_manager._pool.shutdown(wait=True)
         self.assertIsNone(result)
+        self.ack_manager._pool.shutdown(wait=True)
         self.assertTrue(self.listener._received.isSet())
         self.assertEqual(self.message, self.listener.message.message)
         self.assertEqual(3, self.send.call_count)
         self.assertEqual(3, lost_ack_mock.call_count)
         self.assertEqual(1, self.set_result.call_count)
+
+    @mock.patch.object(
+        zmq_incoming_message.ZmqIncomingMessage, 'acknowledge',
+        side_effect=zmq_incoming_message.ZmqIncomingMessage.acknowledge,
+        autospec=True
+    )
+    @mock.patch.object(
+        zmq_incoming_message.ZmqIncomingMessage, 'reply',
+        side_effect=zmq_incoming_message.ZmqIncomingMessage.reply,
+        autospec=True
+    )
+    def test_call_success_without_retries(self, received_reply_mock,
+                                          received_ack_mock):
+        self.listener.listen(self.target)
+        result = self.driver.send(
+            self.target, {}, self.message, wait_for_reply=True, timeout=10
+        )
+        self.assertIsNotNone(result)
+        self.ack_manager._pool.shutdown(wait=True)
+        self.assertTrue(self.listener._received.isSet())
+        self.assertEqual(self.message, self.listener.message.message)
+        self.assertEqual(1, self.send.call_count)
+        self.assertEqual(1, received_ack_mock.call_count)
+        self.assertEqual(3, self.set_result.call_count)
+        received_reply_mock.assert_called_once_with(mock.ANY, reply=True)
+
+    @mock.patch.object(zmq_incoming_message.ZmqIncomingMessage, 'acknowledge')
+    @mock.patch.object(zmq_incoming_message.ZmqIncomingMessage, 'reply')
+    def test_call_failure_exhausted_retries_and_timeout_error(self,
+                                                              lost_reply_mock,
+                                                              lost_ack_mock):
+        self.listener.listen(self.target)
+        self.assertRaises(oslo_messaging.MessagingTimeout,
+                          self.driver.send,
+                          self.target, {}, self.message,
+                          wait_for_reply=True, timeout=20)
+        self.ack_manager._pool.shutdown(wait=True)
+        self.assertTrue(self.listener._received.isSet())
+        self.assertEqual(self.message, self.listener.message.message)
+        self.assertEqual(3, self.send.call_count)
+        self.assertEqual(3, lost_ack_mock.call_count)
+        self.assertEqual(2, self.set_result.call_count)
+        lost_reply_mock.assert_called_once_with(reply=True)
diff --git a/oslo_messaging/tests/drivers/zmq/test_zmq_ttl_cache.py b/oslo_messaging/tests/drivers/zmq/test_zmq_ttl_cache.py
index fa2e2408e..60a5af0ac 100644
--- a/oslo_messaging/tests/drivers/zmq/test_zmq_ttl_cache.py
+++ b/oslo_messaging/tests/drivers/zmq/test_zmq_ttl_cache.py
@@ -35,6 +35,28 @@ class TestZmqTTLCache(test_utils.BaseTestCase):
 
         self.cache = zmq_ttl_cache.TTLCache(ttl=1)
 
+        self.addCleanup(lambda: self.cache.cleanup())
+
+    def _test_add_get(self):
+        self.cache.add('x', 'a')
+
+        self.assertEqual(self.cache.get('x'), 'a')
+        self.assertEqual(self.cache.get('x', 'b'), 'a')
+        self.assertEqual(self.cache.get('y'), None)
+        self.assertEqual(self.cache.get('y', 'b'), 'b')
+
+        time.sleep(1)
+
+        self.assertEqual(self.cache.get('x'), None)
+        self.assertEqual(self.cache.get('x', 'b'), 'b')
+
+    def test_add_get_with_executor(self):
+        self._test_add_get()
+
+    def test_add_get_without_executor(self):
+        self.cache._executor.stop()
+        self._test_add_get()
+
     def _test_in_operator(self):
         self.cache.add(1)
 
@@ -67,15 +89,15 @@ class TestZmqTTLCache(test_utils.BaseTestCase):
         self.cache._executor.stop()
         self._test_in_operator()
 
-    def _is_expired(self, item):
+    def _is_expired(self, key):
         with self.cache._lock:
-            return self.cache._is_expired(self.cache._expiration_times[item],
-                                          time.time())
+            _, expiration_time = self.cache._cache[key]
+            return self.cache._is_expired(expiration_time, time.time())
 
     def test_executor(self):
         self.cache.add(1)
 
-        self.assertEqual([1], sorted(self.cache._expiration_times.keys()))
+        self.assertEqual([1], sorted(self.cache._cache.keys()))
         self.assertFalse(self._is_expired(1))
 
         time.sleep(0.75)
@@ -84,7 +106,7 @@ class TestZmqTTLCache(test_utils.BaseTestCase):
 
         self.cache.add(2)
 
-        self.assertEqual([1, 2], sorted(self.cache._expiration_times.keys()))
+        self.assertEqual([1, 2], sorted(self.cache._cache.keys()))
         self.assertFalse(self._is_expired(1))
         self.assertFalse(self._is_expired(2))
 
@@ -95,12 +117,10 @@ class TestZmqTTLCache(test_utils.BaseTestCase):
         self.cache.add(3)
 
         if 1 in self.cache:
-            self.assertEqual([1, 2, 3],
-                             sorted(self.cache._expiration_times.keys()))
+            self.assertEqual([1, 2, 3], sorted(self.cache._cache.keys()))
             self.assertTrue(self._is_expired(1))
         else:
-            self.assertEqual([2, 3],
-                             sorted(self.cache._expiration_times.keys()))
+            self.assertEqual([2, 3], sorted(self.cache._cache.keys()))
         self.assertFalse(self._is_expired(2))
         self.assertFalse(self._is_expired(3))
 
@@ -108,9 +128,5 @@ class TestZmqTTLCache(test_utils.BaseTestCase):
 
         self.assertEqual(3, self.cache._update_cache.call_count)
 
-        self.assertEqual([3], sorted(self.cache._expiration_times.keys()))
+        self.assertEqual([3], sorted(self.cache._cache.keys()))
         self.assertFalse(self._is_expired(3))
-
-    def cleanUp(self):
-        self.cache.cleanup()
-        super(TestZmqTTLCache, self).cleanUp()