how to use streaming response with anyio stream queue properly

[DeoLeung]

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Example Code

send_stream, recv_stream = create_memory_object_stream[bytes]()
tg = create_task_group()
await tg.__aenter__()
tg.start_soon(generate_messages, send_stream)

async def response_stream():
  async with recv_stream:
    async for message in recv_stream:
      yield message

return StreamingResponse(response_stream(), background=BackgroundTask(tg.__aexit__))

Description

I used to above code to generate the streaming response, my question is

is there a simpler way to fire the generate_messages and leave it running?
or is there a simpler way to manage the task group?

previously I just using the generate_messages as generator and put it into StreamingResponse, but exceptions in AsyncGenerator has many problems, such as async generator ignored GeneratorExit

so I'm thinking the use a simpler queue method as the generator, hopefully to reduce the error and ease the maintenace.

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.112.1

Pydantic Version

2.8.2

Python Version

Python 3.11.9

Additional Context

No response

[YuriiMotov]

I think you don't need that construction. You can just put generate_messages into StreamingResponse.
The reason why you had async generator ignored GeneratorExit error was likely that you were catching all the exceptions (except Exception:).

To avoid such problems, you should catch specific exceptions instead of all exceptions.
Or, you can start with adding except block to re-raise GeneratorExit:

try:
    ...

except GeneratorExit as e: # Add these two lines
    raise e

except Exception as e:
    ...