[FIXED] How to stop start_background_task in Flask-Socket.io

Issue

I have a background process started, but I have no idea how to stop the process. I've read through the documentation but there doesn't seem to be any built in function to kill the task. How should I resolve this? I am specifically referring to the stopCollectingLiveData() section.

@socketio.on('collectLiveData')
def collectLiveData():
    global thread
    with thread_lock:
        if thread is None:
            thread = socketio.start_background_task(background_thread)

def background_thread():
    """Example of how to send server generated events to clients."""
    count = 0
    while True:
        socketio.sleep(1)
        count += 1
        socketio.emit('my_response', {'count': count})

@socketio.on("stopCollectingLiveData")
def stopCollectingLiveData():
    print('')
    socketio.sleep()

Solution

You can stop the background thread with an event object, which you can pass as a parameter. As long as the event is set, the thread runs. When the event is cleared, the thread's execution is suspended.

# ...

from threading import Event

thread_event = Event()

# ...

@socketio.on('collectLiveData')
def collectLiveData():
    global thread
    with thread_lock:
        if thread is None:
            thread_event.set()
            thread = socketio.start_background_task(background_thread, thread_event)

def background_thread(event):
    """Example of how to send server generated events to clients."""
    global thread
    count = 0
    try:
        while event.is_set():
            socketio.sleep(1)
            count += 1
            socketio.emit('my_response', {'count': count})
    finally: 
        event.clear()
        thread = None

@socketio.on("stopCollectingLiveData")
def stopCollectingLiveData():
    global thread
    thread_event.clear()
    with thread_lock:
        if thread is not None:
            thread.join()
            thread = None

Answered By - Detlef