deque.popleft may raise IndexError

celery/events/__init__.py

@@ -52,7 +52,8 @@ class EventDispatcher(object):
     """
 
     def __init__(self, connection=None, hostname=None, enabled=True,
-            channel=None, buffer_while_offline=True, app=None):
+            channel=None, buffer_while_offline=True, app=None,
+            serializer=None):
         self.app = app_or_default(app)
         self.connection = connection
         self.channel = channel
@@ -62,6 +63,7 @@ class EventDispatcher(object):
         self._lock = threading.Lock()
         self.publisher = None
         self._outbound_buffer = deque()
+        self.serializer = serializer or self.app.conf.CELERY_EVENT_SERIALIZER
 
         if self.enabled:
             self.enable()
@@ -70,9 +72,8 @@ class EventDispatcher(object):
         conf = self.app.conf
         self.enabled = True
         channel = self.channel or self.connection.channel()
-        self.publisher = Producer(channel,
-                                  exchange=event_exchange,
-                                  serializer=conf.CELERY_EVENT_SERIALIZER)
+        self.publisher = Producer(channel, exchange=event_exchange,
+                                  serializer=self.serializer)
 
     def disable(self):
         self.enabled = False
@@ -106,7 +107,10 @@ class EventDispatcher(object):
 
     def flush(self):
         while self._outbound_buffer:
-            type, fields, _ = self._outbound_buffer.popleft()
+            try:
+                type, fields, _ = self._outbound_buffer.popleft()
+            except IndexError:
+                return
             self.send(type, **fields)
 
     def copy_buffer(self, other):