我一直在尝试从daphne切换到uvicorn，以便使用django 3和通道进行生产。我在加载通道的经典asgi文件时遇到了错误。由于同步调用django.setup或get_application，我无法使用它。我试图用sync_to_async调用调整这个文件，但没有成功。有人设法做到了吗？
原始asgi.py
代码
import os
import django
from channels.routing import get_default_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "config.settings")
django.setup()
application = get_default_application()
StackTrace
Traceback (most recent call last):
File "/usr/local/lib/python3.8/multiprocessing/process.py", line 315, in _bootstrap
self.run()
File "/usr/local/lib/python3.8/multiprocessing/process.py", line 108, in run
self._target(*self._args, **self._kwargs)
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/uvicorn/subprocess.py", line 61, in subprocess_started
target(sockets=sockets)
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/uvicorn/main.py", line 407, in run
loop.run_until_complete(self.serve(sockets=sockets))
File "/usr/local/lib/python3.8/asyncio/base_events.py", line 612, in run_until_complete
return future.result()
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/uvicorn/main.py", line 414, in serve
config.load()
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/uvicorn/config.py", line 300, in load
self.loaded_app = import_from_string(self.app)
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/uvicorn/importer.py", line 20, in import_from_string
module = importlib.import_module(module_str)
File "/usr/local/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 "./config/asgi.py", line 16, in <module>
django.setup()
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django/__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django/apps/registry.py", line 122, in populate
app_config.ready()
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django_prometheus/apps.py", line 23, in ready
ExportMigrations()
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django_prometheus/migrations.py", line 52, in ExportMigrations
executor = MigrationExecutor(connections[alias])
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django/db/migrations/executor.py", line 18, in __init__
self.loader = MigrationLoader(self.connection)
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django/db/migrations/loader.py", line 49, in __init__
self.build_graph()
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django/db/migrations/loader.py", line 212, in build_graph
self.applied_migrations = recorder.applied_migrations()
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django/db/migrations/recorder.py", line 76, in applied_migrations
if self.has_table():
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/django/db/migrations/recorder.py", line 56, in has_table
return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/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.
修改为asgi.py
代码
import os
import django
from asgiref.sync import sync_to_async
from channels.routing import get_default_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "config.settings")
sync_to_async(django.setup, thread_sensitive=True)
application = sync_to_async(get_default_application, thread_sensitive=True)
Stacktrace
Traceback (most recent call last):
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/uvicorn/lifespan/on.py", line 55, in main
await app(scope, self.receive, self.send)
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/uvicorn/middleware/proxy_headers.py", line 45, in __call__
return await self.app(scope, receive, send)
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/asgiref/sync.py", line 296, in __call__
ret = await asyncio.wait_for(future, timeout=None)
File "/usr/local/lib/python3.8/asyncio/tasks.py", line 455, in wait_for
return await fut
File "/usr/local/lib/python3.8/concurrent/futures/thread.py", line 57, in run
result = self.fn(*self.args, **self.kwargs)
File "/var/www/.cache/pypoetry/virtualenvs/project-4ffvdAoS-py3.8/lib/python3.8/site-packages/asgiref/sync.py", line 334, in thread_handler
return func(*args, **kwargs)
TypeError: get_default_application() takes 0 positional arguments but 3 were given
ERROR: Application startup failed. Exiting.
感谢阅读我的文章伙计们
- 传递给uvicorn的可调用函数将按照此函数在事件循环中运行
- 因为1。
django.setup()需要转换为协同例程 get_default_application()不应该异步运行，它将自动神奇地返回路由器应用程序。这就是uvicorn应该指出的django.setup()必须在主事件循环启动之前返回
给定这四点，您的代码应该如下：
import os
import django
from asgiref.sync import sync_to_async
from channels.routing import get_default_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "config.settings")
await sync_to_async(django.setup, thread_sensitive=True)()
application = get_default_application()
但是，在撰写本文时，您不能将wait用作顶级指令，如果删除它，则不能保证在模块解析之前完成设置(不会(。因此，如果在启动应用程序之前要运行同步代码，则不能使用uvicorn的命令行。
然而，您可以通过程序启动它：
# server.py
import uvicorn
import os
import django
from channels.routing import get_default_application
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "config.settings")
django.setup()
app = get_default_application()
if __name__ == "__main__":
uvicorn.run("server:app") # Pass additional command line options as kwargs
我对这个问题做了一个稍微不同的(在我看来更容易使用(方法，那就是在启动uvicorn服务器之前执行Django东西的同步初始化。
只需创建一个具有执行权限的python文件uvicorn-django，内容如下：
#!/usr/bin/env python
# Patch uvicorn to work properly with django setup
import uvicorn
import importlib
# monkeypatch uvicorn run function to import app before launching server
orig_run = uvicorn.run
def run(*args, **kwargs):
# import application entrypoint before running uvicorn
importlib.import_module(args[0])
orig_run(*args, **kwargs)
uvicorn.run = run
if __name__ == "__main__":
# start uvicorn programmatically after initializing django application
# - django needs to be initialized in non async context (which is not the case if application is started from uvicorn directly)
# - uvicorn.main is the cli (click) implementation that would be executed when starting uvicorn from shell, therefore parsing all the passed arguments as if uvicorn was started directly
uvicorn.main()
通过这种方式，您可以像启动uvicornCLI本身一样使用此python脚本，包括uvicorn提供的所有参数：
$ uvicorn-django --host 0.0.0.0 --port 8080 YOUR_MODULE:YOUR_APPLICATION
另一个解决方案是将gunicorn与uvicorn工作程序一起使用，后者也没有异步问题：
$ gunicorn -k uvicorn.workers.UvicornWorker YOUR_MODULE:YOUR_APPLICATION