Артём Малышев (Positive Technologies) - Django Channels - ответ современному вебу

Доклад с Moscow Python Conf 2016 (http://conf.python.ru)
Видео: https://conf.python.ru/django-channels-otvet-sovremennomu-vebu/

Я senior python developer в компании Positive Technologies. Последние два года занимаюсь разработкой распределённых систем. Спикер PyCon Russia, MoscowPython и Rannts Meetup. В докладе я расскажу о назначение и устройстве Django Channels. Давно прошли времена, когда все сайты работали в режиме "запрос-ответ". Пользователи хотят интерактивности и отзывчивости, программисты хотят websocket'ы, HTTP/2 стремительно набирает популярность. Классические WSGI фреймворки перестают соответствовать реалиям жизни. Вы узнаете каким образом в Django реализована поддержка асинхронных протоколов, решение каких задач можно отдать этой технологии, а где лучше использовать tornado или aiohttp.

Transcript

1. 1
   DJANGO CHANNELS
   ARTEM MALYSHEV
   @PROOFIT404
   

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2. 2
   BRING DJANGO
   TO THE ASYNC
   NETWORKING
   

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3. 3
   BUT WE ARE ALREADY THERE
   twisted
   eventlet
   gevent
   tornado
   asyncio
   

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4. 4
   AND DJANGO
   IS SYNC IN
   ITS CORE
   

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5. 5
   WSGI
   def app(environ, callback):
   status, headers = '200 OK', []
   callback(status, headers)
   return ['Hello world!\n']
   

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7. 7
   OK, BUT IT IS
   2016
   DUDE
   

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8. 8
   PROGRESSIVE WEB APPS
   interactive communication
   responsive design
   push notifications
   works offline
   

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10. 10
    IT'S ALL DIFFERENT
    PERSISTENT
    STATEFUL
    CONNECTIONS
    

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15. 15
    ASGI
    

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16. 16
    ASGI IS
    a standard interface between
    network protocol servers
    and Python applications
    

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17. 17
    CHANNEL
    

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18. 18
    CHANNEL IS
    an ordered,
    first-in first-out queue
    with message expiry
    and at-most-once delivery
    to only one listener at a time
    

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19. 19
    CONSUMERS
    

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20. 20
    ACCEPT WEBSOCKET MESSAGE
    def ws_message(message):
    message.reply_channel.send({
    'text': message.content['text'],
    })
    

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21. 21
    ROUTING
    from channels.routing import route
    from myapp.consumers import ws_message
    channel_routing = [
    route('websocket.receive', ws_message),
    ]
    

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22. 22
    SETTINGS
    CHANNEL_LAYERS = {
    'default': {
    'BACKEND': 'asgiref.inmemory',
    'ROUTING': 'myproject.routing',
    },
    }
    

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23. 23
    ASGI APP
    import os
    from channels.asgi import get_channel_layer
    os.environ.setdefault(
    'DJANGO_SETTINGS_MODULE',
    'myproject.settings',
    )
    channel_layer = get_channel_layer()
    

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24. 24
    DEPLOY
    $ gunicorn myproject.wsgi
    $ daphne myproject.asgi:channel_layer
    $ django-admin runworker
    

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25. 25
    REPLY CHANNEL
    

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27. 27
    GROUPS
    

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28. 28
    CONSUMERS
    from channels import Group
    def ws_connect(message):
    Group('chat').add(message.reply_channel)
    def ws_disconnect(message):
    Group('chat').discard(message.reply_channel)
    def ws_message(message):
    Group('chat').send({
    'text': message.content['text'],
    })
    

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29. 29
    ROUTING
    from channels.routing import route
    from myapp.consumers import *
    channel_routing = [
    route('websocket.connect', ws_connect),
    route('websocket.disconnect', ws_disconnect),
    route('websocket.receive', ws_message),
    ]
    

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30. 30
    GENERIC CONSUMERS
    

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31. 31
    BASE CONSUMER
    from channels.generic import BaseConsumer
    class MyConsumer(BaseConsumer):
    method_mapping = {
    'channel.name.here': 'method_name',
    }
    def method_name(self, message, **kwargs):
    pass
    

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32. 32
    WEBSOCKET CONSUMER
    from channels.generic import WebsocketConsumer
    class MyConsumer(WebsocketConsumer):
    def connection_groups(self):
    return ['chat']
    def connect(self, message):
    pass
    def receive(self, text=None, bytes=None):
    self.send(text=text, bytes=bytes)
    

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33. 33
    ROUTING
    from channels import route_class
    from myapp import consumers
    channel_routing = [
    route_class(consumers.MyConsumer),
    ]
    

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34. 34
    ROUTING
    

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35. 35
    FILTERS
    // app.js
    s = new WebSocket('ws://localhost:8000/chat/')
    # routing.py
    route('websocket.connect', ws_connect,
    path=r'^/chat/$')
    

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36. 36
    INCLUDES
    from channels import route, include
    blog_routes = [
    route('websocket.connect', blog,
    path=r'^/stream/'),
    ]
    routing = [
    include(blog_routes, path=r'^/blog'),
    ]
    

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37. 37
    MULTIPLEXING
    

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38. 38
    DEFINE MAPPING
    from channels import WebsocketDemultiplexer
    class Demultiplexer(WebsocketDemultiplexer):
    mapping = {
    'intval': 'binding.intval',
    }
    

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39. 39
    ROUTING
    from channels import route_class, route
    from .consumers import Demultiplexer, ws_message
    channel_routing = [
    route_class(Demultiplexer, path='^/binding/'),
    route('binding.intval', ws_message),
    ]
    

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40. 40
    MESSAGE CONTENT
    {
    "stream": "intval",
    "payload": {
    ...
    }
    }
    

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41. 41
    SESSIONS
    

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42. 42
    CHANNEL SESSION
    from channels.sessions import channel_session
    @channel_session
    def ws_connect(message):
    room = message.content['path']
    message.channel_session['room'] = room
    Group('chat-%s' % room).add(
    message.reply_channel
    )
    

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43. 43
    HTTP SESSION
    from channels.sessions import http_session_user
    @http_session_user
    def ws_connect(message):
    message.http_session['room'] = room
    if message.user.username:
    ...
    

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44. 44
    MESSAGE ORDER
    

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45. 45
    ENFORCE ORDERING
    from channels.generic import WebsocketConsumer
    class MyConsumer(WebsocketConsumer):
    http_user = True
    slight_ordering = True
    strict_ordering = False
    def connection_groups(self, **kwargs):
    return ['chat']
    

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46. 46
    DATA BINDING
    

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47. 47
    BIND MODEL
    class IntegerValueBinding(WebsocketBinding):
    model = IntegerValue
    stream = 'intval'
    fields = ['name', 'value']
    def group_names(self, instance, action):
    return ['intval-updates']
    def has_permission(self, user, action, pk):
    return True
    

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48. 48
    REDIS LAYER
    

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49. 49
    REDIS LAYER
    SINC ON WORKERS
    ASYNC ON DAPHNE
    MSGPACK
    SHARDING
    

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50. 50
    CHANNEL IMPLEMENTATION
    >> SET "b6dc0dfce" "\x81\xa4text\xachello"
    >> RPUSH "websocket.send!sGOpfny" "b6dc0dfce"
    >> EXPIRE "b6dc0dfce" "60"
    >> EXPIRE "websocket.send!sGOpfny" "61"
    

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51. 51
    GROUP IMPLEMENTATION
    >> type group:chat
    zset
    >> ZRANGE group:chat 0 1 WITHSCORES
    1) "websocket.send!sGOpfny"
    2) "1476199781.8159261"
    

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52. 52
    PROBLEMS
    

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53. 53
    CALLBACK
    HELL
    

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54. 54
    CELERY
    

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55. 55
    CHANNELS
    IS NOT A
    TASK QUEUE
    

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56. 56
    CHANNELS CAN'T
    RETRY
    CANVAS
    ETA
    

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57. 57
    DJANGO
    FOR TODAY'S WEB
    

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58. 58
    QUESTIONS?
    

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