Send messages after the end of consumers

channels/channel.py

@@ -29,13 +29,20 @@ class Channel(object):
         else:
             self.channel_layer = channel_layers[alias]
 
-    def send(self, content):
+    def send(self, content, immediately=False):
         """
         Send a message over the channel - messages are always dicts.
+
+        Sends are delayed until consumer completion. To override this, you
+        may pass immediately=True.
         """
         if not isinstance(content, dict):
             raise TypeError("You can only send dicts as content on channels.")
-        self.channel_layer.send(self.name, content)
+        if immediately:
+            self.channel_layer.send(self.name, content)
+        else:
+            from .message import pending_message_store
+            pending_message_store.append(self, content)
 
     def __str__(self):
         return self.name
@@ -66,7 +73,17 @@ class Group(object):
             channel = channel.name
         self.channel_layer.group_discard(self.name, channel)
 
-    def send(self, content):
+    def send(self, content, immediately=False):
+        """
+        Send a message to all channels in the group.
+
+        Sends are delayed until consumer completion. To override this, you
+        may pass immediately=True.
+        """
         if not isinstance(content, dict):
             raise ValueError("You can only send dicts as content on channels.")
-        self.channel_layer.send_group(self.name, content)
+        if immediately:
+            self.channel_layer.send_group(self.name, content)
+        else:
+            from .message import pending_message_store
+            pending_message_store.append(self, content)

channels/generic/websockets.py

@@ -23,7 +23,7 @@ class WebsocketConsumer(BaseConsumer):
     # implies channel_session_user
     http_user = False
 
-    # Set one to True if you want the class to enforce ordering for you
+    # Set to True if you want the class to enforce ordering for you
     slight_ordering = False
     strict_ordering = False
 
@@ -47,7 +47,7 @@ class WebsocketConsumer(BaseConsumer):
         if self.strict_ordering:
             return enforce_ordering(handler, slight=False)
         elif self.slight_ordering:
-            return enforce_ordering(handler, slight=True)
+            raise ValueError("Slight ordering is now always on. Please remove `slight_ordering=True`.")
         else:
             return handler
 

channels/message.py

@@ -1,7 +1,9 @@
 from __future__ import unicode_literals
 import copy
+import threading
 
 from .channel import Channel
+from .signals import consumer_finished
 
 
 class Message(object):
@@ -58,3 +60,25 @@ class Message(object):
             self.channel.name,
             self.channel_layer,
         )
+
+
+class PendingMessageStore(object):
+    """
+    Singleton object used for storing pending messages that should be sent
+    to a channel or group when a consumer finishes.
+    """
+
+    threadlocal = threading.local()
+
+    def append(self, sender, message):
+        if not hasattr(self.threadlocal, "messages"):
+            self.threadlocal.messages = []
+        self.threadlocal.messages.append((sender, message))
+
+    def send_and_flush(self, **kwargs):
+        for sender, message in getattr(self.threadlocal, "messages", []):
+            sender.send(message, immediately=True)
+        self.threadlocal.messages = []
+
+pending_message_store = PendingMessageStore()
+consumer_finished.connect(pending_message_store.send_and_flush)

channels/sessions.py

@@ -71,15 +71,14 @@ def channel_session(func):
 
 def enforce_ordering(func=None, slight=False):
     """
-    Enforces either slight (order=0 comes first, everything else isn't ordered)
-    or strict (all messages exactly ordered) ordering against a reply_channel.
+    Enforces strict (all messages exactly ordered) ordering against a reply_channel.
 
     Uses sessions to track ordering and socket-specific wait channels for unordered messages.
-
-    You cannot mix slight ordering and strict ordering on a channel; slight
-    ordering does not write to the session after the first message to improve
-    performance.
     """
+    # Slight is deprecated
+    if slight:
+        raise ValueError("Slight ordering is now always on due to Channels changes. Please remove the decorator.")
+    # Main decorator
     def decorator(func):
         @channel_session
         @functools.wraps(func)
@@ -93,13 +92,12 @@ def enforce_ordering(func=None, slight=False):
             order = int(message.content['order'])
             # See what the current next order should be
             next_order = message.channel_session.get("__channels_next_order", 0)
-            if order == next_order or (slight and next_order > 0):
+            if order == next_order:
                 # Run consumer
                 func(message, *args, **kwargs)
                 # Mark next message order as available for running
-                if order == 0 or not slight:
-                    message.channel_session["__channels_next_order"] = order + 1
-                    message.channel_session.save()
+                message.channel_session["__channels_next_order"] = order + 1
+                message.channel_session.save()
                 # Requeue any pending wait channel messages for this socket connection back onto it's original channel
                 while True:
                     wait_channel = "__wait__.%s" % message.reply_channel.name

channels/worker.py

@@ -145,7 +145,7 @@ class Worker(object):
                         break
             except:
                 logger.exception("Error processing message with consumer %s:", name_that_thing(consumer))
-            else:
+            finally:
                 # Send consumer finished so DB conns close etc.
                 consumer_finished.send(sender=self.__class__)