Implement the server side of ZmqDriver

This implements the server side of the driver without modifying the
existing code by allowing the driver to spawn off multiple greenthreads
as before, but queueing any dispatched messages so that the executor
can still do listener.poll() to dispatch messages itself.

This is a hack, but it's a starting point.

Change-Id: Ie299c2695d81d0473cea81d40114326b89de0011

oslo/messaging/_drivers/impl_zmq.py

@@ -14,12 +14,15 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import collections
 import logging
 import os
 import pprint
+import Queue
 import re
 import socket
 import sys
+import threading
 import types
 import uuid
 
@@ -77,7 +80,12 @@ zmq_opts = [
 
     cfg.StrOpt('rpc_zmq_host', default=socket.gethostname(),
                help='Name of this node. Must be a valid hostname, FQDN, or '
-                    'IP address. Must match "host" option, if running Nova.')
+                    'IP address. Must match "host" option, if running Nova.'),
+
+    cfg.IntOpt('rpc_cast_timeout',
+               default=30,
+               help='Seconds to wait before a cast expires (TTL). '
+                    'Only supported by impl_zmq.'),
 ]
 
 CONF = cfg.CONF
@@ -621,7 +629,7 @@ class Connection(rpc_common.Connection):
 
 
 def _cast(addr, context, topic, msg, timeout=None, envelope=False,
-          _msg_id=None):
+          _msg_id=None, allowed_remote_exmods=[]):
     timeout_cast = timeout or CONF.rpc_cast_timeout
     payload = [RpcContext.marshal(context), msg]
 
@@ -639,7 +647,7 @@ def _cast(addr, context, topic, msg, timeout=None, envelope=False,
 
 
 def _call(addr, context, topic, msg, timeout=None,
-          envelope=False):
+          envelope=False, allowed_remote_exmods=[]):
     # timeout_response is how long we wait for a response
     timeout = timeout or CONF.rpc_response_timeout
 
@@ -709,13 +717,14 @@ def _call(addr, context, topic, msg, timeout=None,
     # responses for Exceptions.
     for resp in responses:
         if isinstance(resp, types.DictType) and 'exc' in resp:
-            raise rpc_common.deserialize_remote_exception(CONF, resp['exc'])
+            raise rpc_common.deserialize_remote_exception(
+                resp['exc'], allowed_remote_exmods)
 
     return responses[-1]
 
 
 def _multi_send(method, context, topic, msg, timeout=None,
-                envelope=False, _msg_id=None):
+                envelope=False, _msg_id=None, allowed_remote_exmods=[]):
     """Wraps the sending of messages.
 
     Dispatches to the matchmaker and sends message to all relevant hosts.
@@ -744,7 +753,7 @@ def _multi_send(method, context, topic, msg, timeout=None,
                              _msg_id)
             return
         return method(_addr, context, _topic, msg, timeout,
-                      envelope)
+                      envelope, allowed_remote_exmods)
 
 
 def create_connection(conf, new=True):
@@ -820,6 +829,59 @@ def _get_matchmaker(*args, **kwargs):
     return matchmaker
 
 
+class ZmqIncomingMessage(base.IncomingMessage):
+
+    ReceivedReply = collections.namedtuple(
+        'ReceivedReply', ['reply', 'failure', 'log_failure'])
+
+    def __init__(self, listener, ctxt, message):
+        super(ZmqIncomingMessage, self).__init__(listener, ctxt, message)
+        self.condition = threading.Condition()
+        self.received = None
+
+    def reply(self, reply=None, failure=None, log_failure=True):
+        self.received = self.ReceivedReply(reply, failure, log_failure)
+        with self.condition:
+            self.condition.notify()
+
+
+class ZmqListener(base.Listener):
+
+    def __init__(self, driver, target):
+        super(ZmqListener, self).__init__(driver, target)
+        self.incoming_queue = Queue.Queue()
+
+    def dispatch(self, ctxt, version, method, namespace, **kwargs):
+        message = {
+            'method': method,
+            'args': kwargs
+        }
+        if version:
+            message['version'] = version
+        if namespace:
+            message['namespace'] = namespace
+
+        incoming = ZmqIncomingMessage(self,
+                                      ctxt.to_dict(),
+                                      message)
+
+        self.incoming_queue.put(incoming)
+
+        with incoming.condition:
+            incoming.condition.wait()
+
+        assert incoming.received
+
+        if incoming.received.failure:
+            raise incoming.received.failure
+        else:
+            return incoming.received.reply
+
+    def poll(self):
+        while True:
+            return self.incoming_queue.get()
+
+
 class ZmqDriver(base.BaseDriver):
 
     # FIXME(markmc): allow this driver to be used without eventlet
@@ -869,7 +931,8 @@ class ZmqDriver(base.BaseDriver):
             topic = 'fanout~' + topic
 
         reply = _multi_send(method, context, topic, message,
-                            envelope=envelope)
+                            envelope=envelope,
+                            allowed_remote_exmods=self._allowed_remote_exmods)
 
         if wait_for_reply:
             return reply[-1]
@@ -884,7 +947,18 @@ class ZmqDriver(base.BaseDriver):
         return self._send(target, ctxt, message, envelope=(version == 2.0))
 
     def listen(self, target):
-        raise NotImplementedError()
+        conn = create_connection(self.conf)
+
+        listener = ZmqListener(self, target)
+
+        conn.create_consumer(target.topic, listener)
+        conn.create_consumer('%s.%s' % (target.topic, target.server),
+                             listener)
+        conn.create_consumer(target.topic, listener, fanout=True)
+
+        conn.consume_in_thread()
+
+        return listener
 
     def cleanup(self):
         cleanup()