Start working on a WebSocket interface server

channels/backends/base.py

@@ -1,3 +1,4 @@
+import time
 from channels.consumer_registry import ConsumerRegistry
 
 
@@ -31,10 +32,34 @@ class BaseChannelBackend(object):
 
     def receive_many(self, channels):
         """
-        Block and return the first message available on one of the
-        channels passed, as a (channel, message) tuple.
+        Return the first message available on one of the
+        channels passed, as a (channel, message) tuple, or return (None, None)
+        if no channels are available.
+
+        Should not block, but is allowed to be moderately slow/have a short
+        timeout - it needs to return so we can refresh the list of channels,
+        not because the rest of the process is waiting on it.
+
+        Better performance can be achieved for interface servers by directly
+        integrating the server and the backend code; this is merely for a
+        generic support-everything pattern.
         """
         raise NotImplementedError()
 
+    def receive_many_blocking(self, channels):
+        """
+        Blocking version of receive_many, if the calling context knows it
+        doesn't ever want to change the channels list until something happens.
+
+        This base class provides a default implementation; can be overridden
+        to be more efficient by subclasses.
+        """
+        while True:
+            channel, message = self.receive_many(channels)
+            if channel is None:
+                time.sleep(0.05)
+                continue
+            return channel, message
+
     def __str__(self):
         return self.__class__.__name__

channels/backends/database.py

@@ -60,16 +60,15 @@ class DatabaseChannelBackend(BaseChannelBackend):
     def receive_many(self, channels):
         if not channels:
             raise ValueError("Cannot receive on empty channel list!")
-        while True:
-            # Delete all expired messages (add 10 second grace period for clock sync)
-            self.model.objects.filter(expiry__lt=now() - datetime.timedelta(seconds=10)).delete()
-            # Get a message from one of our channels
-            message = self.model.objects.filter(channel__in=channels).order_by("id").first()
-            if message:
-                self.model.objects.filter(pk=message.pk).delete()
-                return message.channel, json.loads(message.content)
-            # If all empty, sleep for a little bit
-            time.sleep(0.1)
+        # Delete all expired messages (add 10 second grace period for clock sync)
+        self.model.objects.filter(expiry__lt=now() - datetime.timedelta(seconds=10)).delete()
+        # Get a message from one of our channels
+        message = self.model.objects.filter(channel__in=channels).order_by("id").first()
+        if message:
+            self.model.objects.filter(pk=message.pk).delete()
+            return message.channel, json.loads(message.content)
+        else:
+            return None, None
 
     def __str__(self):
         return "%s(alias=%s)" % (self.__class__.__name__, self.connection.alias)

channels/backends/memory.py

@@ -22,15 +22,13 @@ class InMemoryChannelBackend(BaseChannelBackend):
     def receive_many(self, channels):
         if not channels:
             raise ValueError("Cannot receive on empty channel list!")
-        while True:
-            # Try to pop a message from each channel
-            for channel in channels:
-                try:
-                    # This doesn't clean up empty channels - OK for testing.
-                    # For later versions, have cleanup w/lock.
-                    return channel, queues[channel].popleft()
-                except (IndexError, KeyError):
-                    pass
-            # If all empty, sleep for a little bit
-            time.sleep(0.01)
+        # Try to pop a message from each channel
+        for channel in channels:
+            try:
+                # This doesn't clean up empty channels - OK for testing.
+                # For later versions, have cleanup w/lock.
+                return channel, queues[channel].popleft()
+            except (IndexError, KeyError):
+                pass
+        return None, None
 

channels/channel.py

@@ -18,12 +18,15 @@ class Channel(object):
     "default" one by default.
     """
 
-    def __init__(self, name, alias=DEFAULT_CHANNEL_BACKEND):
+    def __init__(self, name, alias=DEFAULT_CHANNEL_BACKEND, channel_backend=None):
         """
         Create an instance for the channel named "name"
         """
         self.name = name
-        self.channel_backend = channel_backends[alias]
+        if channel_backend:
+            self.channel_backend = channel_backend
+        else:
+            self.channel_backend = channel_backends[alias]
 
     def send(self, **kwargs):
         """

channels/interfaces/websocket_twisted.py

@@ -0,0 +1,106 @@
+import django
+import time
+from collections import deque
+from twisted.internet import reactor
+from channels import Channel, channel_backends, DEFAULT_CHANNEL_BACKEND
+from autobahn.twisted.websocket import WebSocketServerProtocol, WebSocketServerFactory
+
+
+class InterfaceProtocol(WebSocketServerProtocol):
+    """
+    Protocol which supports WebSockets and forwards incoming messages to
+    the django.websocket channels.
+    """
+
+    def onConnect(self, request):
+        self.channel_backend = channel_backends[DEFAULT_CHANNEL_BACKEND]
+        self.request = request
+
+    def onOpen(self):
+        # Make sending channel
+        self.send_channel = Channel.new_name("django.websocket.send")
+        self.factory.protocols[self.send_channel] = self
+        # Send news that this channel is open
+        Channel("django.websocket.connect").send(
+            send_channel = self.send_channel,
+        )
+
+    def onMessage(self, payload, isBinary):
+        if isBinary:
+            Channel("django.websocket.receive").send(
+                send_channel = self.send_channel,
+                content = payload,
+                binary = True,
+            )
+        else:
+            Channel("django.websocket.receive").send(
+                send_channel = self.send_channel,
+                content = payload.decode("utf8"),
+                binary = False,
+            )
+
+    def onChannelSend(self, content, binary=False, **kwargs):
+        self.sendMessage(content, binary)
+
+    def onClose(self, wasClean, code, reason):
+        del self.factory.protocols[self.send_channel]
+        Channel("django.websocket.disconnect").send(
+            send_channel = self.send_channel,
+        )
+
+
+class InterfaceFactory(WebSocketServerFactory):
+    """
+    Factory which keeps track of its open protocols' receive channels
+    and can dispatch to them.
+    """
+
+    # TODO: Clean up dead protocols if needed?
+
+    def __init__(self, *args, **kwargs):
+        super(InterfaceFactory, self).__init__(*args, **kwargs)
+        self.protocols = {}
+
+    def send_channels(self):
+        return self.protocols.keys()
+
+    def dispatch_send(self, channel, message):
+        self.protocols[channel].onChannelSend(**message)
+
+
+class WebsocketTwistedInterface(object):
+    """
+    Easy API to run a WebSocket interface server using Twisted.
+    Integrates the channel backend by running it in a separate thread, as we don't
+    know if the backend is Twisted-compliant.
+    """
+
+    def __init__(self, channel_backend, port=9000):
+        self.channel_backend = channel_backend
+        self.port = port
+
+    def run(self):
+        self.factory = InterfaceFactory("ws://localhost:%i" % self.port, debug=False)
+        self.factory.protocol = InterfaceProtocol
+        reactor.listenTCP(self.port, self.factory)
+        reactor.callInThread(self.backend_reader)
+        reactor.run()
+
+    def backend_reader(self):
+        """
+        Run in a separate thread; reads messages from the backend.
+        """
+        while True:
+            channels = self.factory.send_channels()
+            # Don't do anything if there's no channels to listen on
+            if channels:
+                channel, message = self.channel_backend.receive_many(channels)
+            else:
+                time.sleep(0.1)
+                continue
+            # Wait around if there's nothing received
+            if channel is None:
+                time.sleep(0.05)
+                continue
+            # Deal with the message
+            self.factory.dispatch_send(channel, message)

channels/interfaces/wsgi.py

@@ -0,0 +1,21 @@
+import django
+from django.core.handlers.wsgi import WSGIHandler
+from django.http import HttpResponse
+from channels import Channel
+
+
+class WSGIInterface(WSGIHandler):
+    """
+    WSGI application that pushes requests to channels.
+    """
+
+    def __init__(self, channel_backend, *args, **kwargs):
+        self.channel_backend = channel_backend
+        django.setup()
+        super(WSGIInterface, self).__init__(*args, **kwargs)
+
+    def get_response(self, request):
+        request.response_channel = Channel.new_name("django.wsgi.response")
+        Channel("django.wsgi.request", channel_backend=self.channel_backend).send(**request.channel_encode())
+        channel, message = self.channel_backend.receive_many_blocking([request.response_channel])
+        return HttpResponse.channel_decode(message)

channels/management/commands/runserver.py

@@ -2,12 +2,11 @@ import django
 import threading
 from django.core.management.commands.runserver import Command as RunserverCommand
 from django.core.management import CommandError
-from django.core.handlers.wsgi import WSGIHandler
-from django.http import HttpResponse
-from channels import Channel, channel_backends, DEFAULT_CHANNEL_BACKEND
+from channels import channel_backends, DEFAULT_CHANNEL_BACKEND
 from channels.worker import Worker
 from channels.utils import auto_import_consumers
 from channels.adapters import UrlConsumer
+from channels.interfaces.wsgi import WSGIInterface
 
 
 class Command(RunserverCommand):
@@ -16,38 +15,25 @@ class Command(RunserverCommand):
         """
         Returns the default WSGI handler for the runner.
         """
-        django.setup()
-        return WSGIInterfaceHandler()
+        return WSGIInterface(self.channel_backend)
 
     def run(self, *args, **options):
         # Force disable reloader for now
         options['use_reloader'] = False
         # Check a handler is registered for http reqs
-        channel_backend = channel_backends[DEFAULT_CHANNEL_BACKEND]
+        self.channel_backend = channel_backends[DEFAULT_CHANNEL_BACKEND]
         auto_import_consumers()
-        if not channel_backend.registry.consumer_for_channel("django.wsgi.request"):
+        if not self.channel_backend.registry.consumer_for_channel("django.wsgi.request"):
             # Register the default one
-            channel_backend.registry.add_consumer(UrlConsumer(), ["django.wsgi.request"])
+            self.channel_backend.registry.add_consumer(UrlConsumer(), ["django.wsgi.request"])
         # Launch a worker thread
-        worker = WorkerThread(channel_backend)
+        worker = WorkerThread(self.channel_backend)
         worker.daemon = True
         worker.start()
         # Run the rest
         return super(Command, self).run(*args, **options)
 
 
-class WSGIInterfaceHandler(WSGIHandler):
-    """
-    New WSGI handler that pushes requests to channels.
-    """
-
-    def get_response(self, request):
-        request.response_channel = Channel.new_name("django.wsgi.response")
-        Channel("django.wsgi.request").send(**request.channel_encode())
-        channel, message = channel_backends[DEFAULT_CHANNEL_BACKEND].receive_many([request.response_channel])
-        return HttpResponse.channel_decode(message)
-
-
 class WorkerThread(threading.Thread):
     """
     Class that runs a worker

channels/management/commands/runwsserver.py

@@ -0,0 +1,25 @@
+import time
+from django.core.management import BaseCommand, CommandError
+from channels import channel_backends, DEFAULT_CHANNEL_BACKEND
+from channels.interfaces.websocket_twisted import WebsocketTwistedInterface
+from channels.utils import auto_import_consumers
+
+
+class Command(BaseCommand):
+
+    def handle(self, *args, **options):
+        # Get the backend to use
+        channel_backend = channel_backends[DEFAULT_CHANNEL_BACKEND]
+        auto_import_consumers()
+        if channel_backend.local_only:
+            raise CommandError(
+                "You have a process-local channel backend configured, and so cannot run separate interface servers.\n"
+                "Configure a network-based backend in CHANNEL_BACKENDS to use this command."
+            )
+        # Launch a worker
+        self.stdout.write("Running Twisted/Autobahn WebSocket interface against backend %s" % channel_backend)
+        # Run the interface
+        try:
+            WebsocketTwistedInterface(channel_backend=channel_backend).run()
+        except KeyboardInterrupt:
+            pass

channels/worker.py

@@ -1,3 +1,6 @@
+import time
+
+
 class Worker(object):
     """
     A "worker" process that continually looks for available messages to run
@@ -12,10 +15,10 @@ class Worker(object):
         """
         Tries to continually dispatch messages to consumers.
         """
-
         channels = self.channel_backend.registry.all_channel_names()
         while True:
-            channel, message = self.channel_backend.receive_many(channels)
+            channel, message = self.channel_backend.receive_many_blocking(channels)
+            # Handle the message
             consumer = self.channel_backend.registry.consumer_for_channel(channel)
             if self.callback:
                 self.callback(channel, message)