How to run examples using Uvicorn?

[Scypio81]

Hi, I'm trying to learn how to use django-eventstream by running examples. But trying to use Uvicorn results only in getting asyncio errors. Is there a way to run them using Uvicorn?

Sorry if this is inappropriate question here.

[jkarneges]

What error do you get? Uvicorn 0.27.1 works for me with the chat example, by adding whitenoise (to make static files work) and then running:

uvicorn server.asgi:application

[Scypio81]

The problem:

1. python manage.py runserver - goes with a bunch of DB warnings ("Accessing the database during app initialization is discouraged") but works fine, example runs on http://127.0.0.1:8000/ and browser shows the time updates nicely.
2. uvicorn server.asgi:application --host 0.0.0.0 --port 4001 - crashes with SynchronousOnlyOperation error.

My best guess is this is somehow related to the DB warnings and I need to change something there? Like driver for async sqlite? I'm missing a step here, sorry.

Versions:

• Python 3.10
• Django==5.0.2
• django-eventstream==5.0.0
• uvicorn==0.27.1

Command I use to run: uvicorn server.asgi:application --host 0.0.0.0 --port 4001

Error: django.core.exceptions.SynchronousOnlyOperation: You cannot call this from an async context - use a thread or sync_to_async. Error trace:

Traceback (most recent call last):
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/bin/uvicorn", line 8, in <module>
    sys.exit(main())
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/uvicorn/main.py", line 418, in main
    run(
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/uvicorn/main.py", line 587, in run
    server.run()
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/uvicorn/server.py", line 62, in run
    return asyncio.run(self.serve(sockets=sockets))
  File "/usr/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.10/asyncio/base_events.py", line 649, in run_until_complete
    return future.result()
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/uvicorn/server.py", line 69, in serve
    config.load()
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/uvicorn/config.py", line 458, in load
    self.loaded_app = import_from_string(self.app)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/uvicorn/importer.py", line 21, in import_from_string
    module = importlib.import_module(module_str)
  File "/usr/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/django-eventstream/examples/time/server/asgi.py", line 23, in <module>
    application = get_asgi_application()
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/core/asgi.py", line 12, in get_asgi_application
    django.setup(set_prefix=False)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/apps/registry.py", line 124, in populate
    app_config.ready()
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/django-eventstream/examples/time/timeapp/apps.py", line 12, in ready
    ensure_worker_started()
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/django-eventstream/examples/time/timeapp/apps.py", line 24, in ensure_worker_started
    if not is_db_ready():
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/django-eventstream/examples/time/timeapp/apps.py", line 47, in is_db_ready
    Event.objects.count()
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/db/models/query.py", line 620, in count
    return self.query.get_count(using=self.db)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/db/models/sql/query.py", line 629, in get_count
    return obj.get_aggregation(using, {"__count": Count("*")})["__count"]
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/db/models/sql/query.py", line 615, in get_aggregation
    result = compiler.execute_sql(SINGLE)
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 1560, in execute_sql
    cursor = self.connection.cursor()
  File "/media/Storage/_SRC/PYTHON/django_eventstream_example/my_venv/lib/python3.10/site-packages/django/utils/asyncio.py", line 24, in inner
    raise SynchronousOnlyOperation(message)
django.core.exceptions.SynchronousOnlyOperation: You cannot call this from an async context - use a thread or sync_to_async.

[jkarneges]

Ah yeah, the time example tries to access the DB during startup. Offhand I'm not sure of the proper way to fix that, but you could try moving the ensure_worker_started() call from the app ready method to the view handler, so that the DB isn't accessed until the first request. You could also try the chat example.

[Scypio81]

Thanks, I'll try. Thank you for your help.