Add 'in_memory' messaging backend and use it during build_module_locally to drop dependency on fedmsg-relay for local builds.

module_build_service/messaging.py

@@ -33,7 +33,7 @@ except ImportError:
     from funcsigs import signature
 
 from module_build_service import log
-
+import queue
 
 class BaseMessage(object):
     def __init__(self, msg_id):
@@ -330,6 +330,39 @@ def _amq_publish(topic, msg, conf, service):
     msngr.put(message)
     msngr.send()
 
+# Queue for "in_memory" messaging.
+_in_memory_work_queue = queue.Queue()
+
+# Message id for "in_memory" messaging.
+_in_memory_msg_id = 0
+
+def _in_memory_publish(topic, msg, conf, service):
+    """
+    Puts the message to _in_memory_work_queue".
+    """
+
+    # Increment the message ID.
+    global _in_memory_msg_id
+    _in_memory_msg_id += 1
+
+    # Create fake fedmsg from the message so we can reuse
+    # the BaseMessage.from_fedmsg code to get the particular BaseMessage
+    # class instance.
+    topic = service + "." + topic
+    wrapped_msg = {}
+    wrapped_msg["msg_id"] = str(_in_memory_msg_id)
+    wrapped_msg["msg"] = msg
+    wrapped_msg = BaseMessage.from_fedmsg(topic, wrapped_msg)
+
+    # Put the message to queue.
+    _in_memory_work_queue.put(wrapped_msg)
+
+def _in_memory_listen(conf, **kwargs):
+    """
+    Yields the message from the _in_memory_work_queue when ready.
+    """
+    while True:
+        yield _in_memory_work_queue.get(True)
 
 _messaging_backends = {
     'fedmsg': {
@@ -340,4 +373,8 @@ _messaging_backends = {
         'publish': _amq_publish,
         'listen': _amq_listen,
     },
+    'in_memory': {
+        'publish': _in_memory_publish,
+        'listen': _in_memory_listen,
+    },
 }