Comment connecter un sujet kafka avec un point de terminaison Web à l'aide du package Faust Python?

9

J'ai une application simple, avec deux fonctions, l'une pour écouter le sujet et l'autre pour le point de terminaison Web. Je veux créer un flux d'événements côté serveur (SSE), c'est-à-dire du texte / flux d'événements, afin que du côté client, je puisse l'écouter en utilisant EventSource.

J'ai le code suivant pour l'instant, où chaque fonction fait son travail particulier:

import faust

from faust.web import Response

app = faust.App("app1", broker="kafka://localhost:29092", value_serializer="raw")
test_topic = app.topic("test")


@app.agent(test_topic)
async def test_topic_agent(stream):
    async for value in stream:
        print(f"test_topic_agent RECEIVED -- {value!r}")
        yield value


@app.page("/")
async def index(self, request):
    return self.text("yey")

Maintenant, je veux dans l'index, quelque chose comme ce code, mais en utilisant faust:

import asyncio
from aiohttp import web
from aiohttp.web import Response
from aiohttp_sse import sse_response
from datetime import datetime


async def hello(request):
    loop = request.app.loop
    async with sse_response(request) as resp:
        while True:
            data = 'Server Time : {}'.format(datetime.now())
            print(data)
            await resp.send(data)
            await asyncio.sleep(1, loop=loop)
    return resp


async def index(request):
    d = """
        <html>
        <body>
            <script>
                var evtSource = new EventSource("/hello");
                evtSource.onmessage = function(e) {
                    document.getElementById('response').innerText = e.data
                }
            </script>
            <h1>Response from server:</h1>
            <div id="response"></div>
        </body>
    </html>
    """
    return Response(text=d, content_type='text/html')


app = web.Application()
app.router.add_route('GET', '/hello', hello)
app.router.add_route('GET', '/', index)
web.run_app(app, host='127.0.0.1', port=8080)

J'ai essayé ceci:

import faust

from faust.web import Response

app = faust.App("app1", broker="kafka://localhost:29092", value_serializer="raw")
test_topic = app.topic("test")


# @app.agent(test_topic)
# async def test_topic_agent(stream):
#     async for value in stream:
#         print(f"test_topic_agent RECEIVED -- {value!r}")
#         yield value


@app.page("/", name="t1")
@app.agent(test_topic, name="t")
async def index(self, request):
    return self.text("yey")

Mais cela me donne l'erreur suivante:

Traceback (most recent call last):
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/cli/base.py", line 299, in find_app
    val = symbol_by_name(app, imp=imp)
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/utils/imports.py", line 262, in symbol_by_name
    module = imp(  # type: ignore
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/utils/imports.py", line 376, in import_from_cwd
    return imp(module, package=package)
  File "/Users/maverick/.pyenv/versions/3.8.1/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/Users/maverick/company/demo1/baiohttp-demo/app1.py", line 18, in <module>
    async def index(self, request):
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/app/base.py", line 1231, in _decorator
    view = view_base.from_handler(cast(ViewHandlerFun, fun))
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/web/views.py", line 50, in from_handler
    return type(fun.__name__, (cls,), {
AttributeError: 'Agent' object has no attribute '__name__'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/maverick/.pyenv/versions/faust_demo/bin/faust", line 8, in <module>
    sys.exit(cli())
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/click/core.py", line 781, in main
    with self.make_context(prog_name, args, **extra) as ctx:
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/cli/base.py", line 407, in make_context
    self._maybe_import_app()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/cli/base.py", line 372, in _maybe_import_app
    find_app(appstr)
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/cli/base.py", line 303, in find_app
    val = imp(app)
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/utils/imports.py", line 376, in import_from_cwd
    return imp(module, package=package)
  File "/Users/maverick/.pyenv/versions/3.8.1/lib/python3.8/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/Users/maverick/company/demo1/baiohttp-demo/app1.py", line 18, in <module>
    async def index(self, request):
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/app/base.py", line 1231, in _decorator
    view = view_base.from_handler(cast(ViewHandlerFun, fun))
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/web/views.py", line 50, in from_handler
    return type(fun.__name__, (cls,), {
AttributeError: 'Agent' object has no attribute '__name__'

J'ai essayé ceci:

import faust

from faust.web import Response

app = faust.App("app1", broker="kafka://localhost:29092", value_serializer="raw")
test_topic = app.topic("test")


# @app.agent(test_topic)
# async def test_topic_agent(stream):
#     async for value in stream:
#         print(f"test_topic_agent RECEIVED -- {value!r}")
#         yield value


@app.agent(test_topic, name="t")
@app.page("/", name="t1")
async def index(self, request):
    return self.text("yey")

Mais j'obtiens l'erreur suivante:

[2020-03-28 10:32:50,676] [29976] [INFO] [^--Producer]: Creating topic 'app1-__assignor-__leader'
[2020-03-28 10:32:50,695] [29976] [INFO] [^--ReplyConsumer]: Starting...
[2020-03-28 10:32:50,695] [29976] [INFO] [^--AgentManager]: Starting...
[2020-03-28 10:32:50,695] [29976] [INFO] [^---Agent: app1.index]: Starting...
[2020-03-28 10:32:50,696] [29976] [ERROR] [^Worker]: Error: TypeError("__init__() missing 1 required positional argument: 'web'")
Traceback (most recent call last):
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/worker.py", line 273, in execute_from_commandline
    self.loop.run_until_complete(self._starting_fut)
  File "/Users/maverick/.pyenv/versions/3.8.1/lib/python3.8/asyncio/base_events.py", line 612, in run_until_complete
    return future.result()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 736, in start
    await self._default_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 743, in _default_start
    await self._actually_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 767, in _actually_start
    await child.maybe_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 795, in maybe_start
    await self.start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 736, in start
    await self._default_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 743, in _default_start
    await self._actually_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 767, in _actually_start
    await child.maybe_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 795, in maybe_start
    await self.start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 736, in start
    await self._default_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 743, in _default_start
    await self._actually_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 760, in _actually_start
    await self.on_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/agents/manager.py", line 58, in on_start
    await agent.maybe_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 795, in maybe_start
    await self.start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 736, in start
    await self._default_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 743, in _default_start
    await self._actually_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/mode/services.py", line 760, in _actually_start
    await self.on_start()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/agents/agent.py", line 282, in on_start
    await self._on_start_supervisor()
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/agents/agent.py", line 312, in _on_start_supervisor
    res = await self._start_one(
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/agents/agent.py", line 251, in _start_one
    return await self._start_task(
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/agents/agent.py", line 617, in _start_task
    actor = self(
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/agents/agent.py", line 525, in __call__
    return self.actor_from_stream(stream,
  File "/Users/maverick/.pyenv/versions/3.8.1/envs/faust_demo/lib/python3.8/site-packages/faust/agents/agent.py", line 552, in actor_from_stream
    res = self.fun(actual_stream)
TypeError: __init__() missing 1 required positional argument: 'web'
[2020-03-28 10:32:50,703] [29976] [INFO] [^Worker]: Stopping...
[2020-03-28 10:32:50,703] [29976] [INFO] [^-App]: Stopping...
[2020-03-28 10:32:50,703] [29976] [INFO] [^-App]: Flush producer buffer...
[2020-03-28 10:32:50,703] [29976] [INFO] [^--TableManager]: Stopping...

Pourrait-il y avoir un moyen pour cela? Merci beaucoup d'avance!

python  python-3.x  apache-kafka  aiohttp  faust 
— Maverick
source
Aucune expérience avec AIOHttp, mais je suggère d'essayer SocketIO
— cricket_007
'Agent' object has no attribute '__name__'... Avez-vous essayé de supprimer name="t"?
— cricket_007
Oui, j'ai essayé de supprimer name="t"doesnt help, même erreur. @ cricket_007
— Maverick
Avez-vous pu obtenir que Faust imprime des messages vers le terminal? L'erreur n'a rien à voir avec le SSE
— cricket_007
2
J'essaie de vous aider à déboguer. : / 1) Je ne connais pas le problème 2) Veuillez prouver que vous pouvez réellement lire les messages du sujet en montrant un exemple reproductible minimal
— cricket_007

Réponses:

4

L'ouvrier Faust exposera également un serveur Web sur chaque instance, qui s'exécute par défaut sur le port 6066.

Le serveur utilisera la bibliothèque de serveur HTTP aiohttp et vous pouvez profiter de cette chose et créer un flux d'événements côté serveur (SSE) comme dans votre exemple de code.

Vous pouvez créer un agent qui lira à partir du sujet Kafka testet mettra à jour une variable last_message_from_topicavec le dernier message du sujet, cette variable sera également visible à partir de vos pages Web.

Dans la page d'index ( @app.page('/')), l'interface EventSource est utilisée pour recevoir les événements envoyés par le serveur. Il se connecte au serveur via HTTP et reçoit des événements au format texte / flux d'événements depuis la page /hellosans fermer la connexion.

La page Web /helloenvoie à chaque seconde un texte de message avec le dernier message du sujet Kafka testet l'heure actuelle du serveur.

voici mon my_worker.pycode de fichier :

import asyncio
from datetime import datetime

import faust
from aiohttp.web import Response
from aiohttp_sse import sse_response

app = faust.App(
    "app1",
    broker='kafka://localhost:9092',
    value_serializer='json',
)
test_topic = app.topic("test")

last_message_from_topic = ['No messages yet']


@app.agent(test_topic)
async def greet(greetings):
    async for greeting in greetings:
        last_message_from_topic[0] = greeting


@app.page('/hello')
async def hello(self, request):
    loop = request.app.loop
    async with sse_response(request) as resp:
        while True:
            data = f'last message from topic_test: {last_message_from_topic[0]} | '
            data += f'Server Time : {datetime.now()}'

            print(data)
            await resp.send(data)
            await asyncio.sleep(1, loop=loop)
    return resp


@app.page('/')
async def index(self, request):
    d = """
        <html>
        <body>
            <script>
                var evtSource = new EventSource("/hello");
                evtSource.onmessage = function(e) {
                    document.getElementById('response').innerText = e.data
                }
            </script>
            <h1>Response from server:</h1>
            <div id="response"></div>
        </body>
    </html>
    """
    return Response(text=d, content_type='text/html')

vous devez maintenant démarrer l'ouvrier Faust avec la commande suivante:

faust -A my_worker worker -l info

sur votre navigateur Web, vous pouvez accéder à http://localhost:6066/:

entrez la description de l'image ici

voici le code pour envoyer des messages à Kafka sur le sujet test(à partir d'un autre fichier python):

import time
import json

from kafka import  KafkaProducer

producer = KafkaProducer(bootstrap_servers=['localhost:9092'],value_serializer=lambda x: json.dumps(x).encode('utf-8'))


for i in range(220):
    time.sleep(1)
    producer.send('test', value=f'Some message from kafka id {i}')
— kederrac
source
1

La lecture de la documentation Web faust ne semble pas gérer SSE.

@app.agentest rappelé lorsqu'un message kafka est consommé et @app.pagelorsqu'une demande http est traitée. Leur combinaison n'est probablement pas possible.

Une autre approche à l'aide faust.webconsiste à interroger à partir du javascript.
Par exemple en utilisant:

import faust
from faust.web import Response

app = faust.App("myapp", broker="kafka://kafka:9092", value_serializer="raw")
test_topic = app.topic("test")
app.lastmsg = ""

@app.agent(test_topic)
async def test_topic_agent(stream):
    async for value in stream:
        app.lastmsg = str(value)
        yield value

@app.page("/msg")
async def msg(self, request):
    return self.text(app.lastmsg)

@app.page("/")
async def index(self, request):
    body = """
        <html>
        <body>
            <script>
                setInterval(()=>{
                    let xhr = new XMLHttpRequest();
                    xhr.open('GET', '/msg');
                    xhr.send();
                    xhr.onload = function() {
                        if (xhr.status == 200) {
                            document.getElementById('response').innerText = xhr.response
                        }
                    }
                },1000);
            </script>
            <h1>Response from server:</h1>
            <div id="response"></div>
        </body>
    </html>
    """
    return self.html(body)

Cette implémentation naïve stocke le message kafka app.lastmsgqui pourrait être obtenu par l'API /msg.

Pour utiliser SSE, vous pouvez l'utiliser asynciopour le composant WebPart et faustpour le consommateur Kafka.

— mpromonet
source
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