issue #212: service: support no_reply decorator.

mitogen/service.py

@@ -120,6 +120,18 @@ def expose(policy):
     return wrapper
 
 
+def no_reply():
+    """
+    Annotate a method as one that does not generate a response. Messages sent
+    by the method are done so explicitly. This can be used for fire-and-forget
+    endpoints where the requestee never receives a reply.
+    """
+    def wrapper(func):
+        func.mitogen_service__no_reply = True
+        return func
+    return wrapper
+
+
 class Service(object):
     #: Sentinel object to suppress reply generation, since returning ``None``
     #: will trigger a response message containing the pickled ``None``.
@@ -179,7 +191,20 @@ class Service(object):
         method = getattr(self, method_name)
         if 'msg' in method.func_code.co_varnames:
             kwargs['msg'] = msg  # TODO: hack
-        return method(**kwargs)
+
+        no_reply = getattr(method, 'mitogen_service__no_reply', False)
+        ret = None
+        try:
+            ret = method(**kwargs)
+            if no_reply:
+                return self.NO_REPLY
+            return ret
+        except Exception:
+            if no_reply:
+                LOG.exception('While calling no-reply method %s.%s',
+                              type(self).__name__, method.func_name)
+            else:
+                raise
 
     def on_receive_message(self, msg):
         try: