Starlette: accumulated tasks. Why?

[DeaD_EyE]

The BackgroundTasks are not deleted when the tasks has been finished, so it's executing all time all existing tasks.

Remove line 32: tasks = BackgroundTasks()

In line 23 replace:

task = BackgroundTask(parse_json, json_data)

# don't forget to import BackgroundTask
# don't use BackgroundTasks

And change

    return JSONResponse({"status": "OK"}, background=tasks, status_code=200)

to

    return JSONResponse({"status": "OK"}, background=task, status_code=200)

Output:
INFO:     Application startup complete.
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     127.0.0.1:61469 - "POST /testbground HTTP/1.1" 200 OK
5
INFO:     127.0.0.1:61471 - "POST /testbground HTTP/1.1" 200 OK
6
INFO:     127.0.0.1:61474 - "POST /testbground HTTP/1.1" 200 OK
0
INFO:     127.0.0.1:61476 - "POST /testbground HTTP/1.1" 200 OK
1
INFO:     127.0.0.1:61478 - "POST /testbground HTTP/1.1" 200 OK
2
INFO:     127.0.0.1:61480 - "POST /testbground HTTP/1.1" 200 OK
3
INFO:     127.0.0.1:61482 - "POST /testbground HTTP/1.1" 200 OK
4

The implementation of these classes are simple: https://github.com/encode/starlette/blob...ound.py#L7
The Response class takes the background and run it as a coroutine or as a thread if it's not a coroutine.

Why the error happens, is also self-explanatory. In BackgroundTasks class is no automagically method to remove a task.