Django Async Safety Issue Analysis

The issue you're experiencing is related to Django's async safety mechanisms and how you're mixing synchronous and asynchronous code in your application.

The Root Problem

Looking at your code example:

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import asyncio
from asgiref.sync import async_to_sync

async def wait():
    await asyncio.sleep(1)

def get_publickey(request):
    time.sleep(50)  # Blocking the thread for 50 seconds
    async_to_sync(wait)()  # Trying to run async code from sync context
    return HttpResponse(json.dumps({}))

There are several issues here:

1. You're using a long-running synchronous operation (time.sleep(50)) which blocks the thread completely
2. After blocking the thread, you're trying to use async_to_sync to run an async function
3. When running under Daphne (an ASGI server), this creates thread management problems

Why This Happens

Daphne is an ASGI server that expects to work with asynchronous code. When you have a view function like get_publickey that:

1. Blocks for a long time (50 seconds)
2. Then tries to use async_to_sync

The server's application timeout mechanism kicks in because your function is taking too long to complete. The "took too long to shut down and was killed" message indicates that Daphne is forcibly terminating your application's processing.

How to Fix It

You have a few options:

Option 1: Make your view fully asynchronous

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import asyncio
import json
from django.http import HttpResponse

async def get_publickey(request):
    await asyncio.sleep(50)  # Non-blocking sleep
    await asyncio.sleep(1)   # Your wait function
    return HttpResponse(json.dumps({}))

Option 2: Use sync_to_async for the entire view

If you need to keep synchronous code:

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import asyncio
import time
import json
from asgiref.sync import sync_to_async
from django.http import HttpResponse

def sync_get_publickey():
    time.sleep(50)
    # Do other sync operations
    return json.dumps({})

async def get_publickey(request):
    result = await sync_to_async(sync_get_publickey)()
    return HttpResponse(result)

Option 3: Adjust your Daphne timeout settings

While this won't fix the underlying issue, you could increase the timeout values:

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daphne health_inspect.asgi:application --bind 127.0.0.1 --port 8002 --application_close_timeout 60

Best Practices

1. Avoid mixing sync and async code directly - use the appropriate wrappers
2. Don't use blocking operations like time.sleep() in Django views when using ASGI servers
3. Be aware that async_to_sync relies on proper thread management, which can be disrupted by long-running sync operations

This isn't necessarily a bug in Daphne, but rather an issue with how your code is structured in relation to Django's async safety mechanisms and Daphne's expectations for handling requests.