Check if a thread is still running in Python Threading

Question

I have a Flask API where every time a POST request is sent to a specific URL, the job is put on a thread to run in parallel so that my request can continue its work. However, if a user sends multiple POST requests, the function will start the same jobs on several threads and I don't want that. I want only one thread to run and if other requests comes, I want it to send a message to the user saying a thread is already running instead of joining the thread. For that to happen, I need to check if the Thread is still alive and then execute my code. But I am having issues with that.

I achieved the following:

# [POST] Post a tweet in database
@jwt_required
def post(self):
    # Get json body from post request
    body = request.get_json()

    # Verify body format
    try:
        # Checks data
        value = body["value_flag"]

        if value == "start_live_tweet_streaming":

            stream = Coroutine.Thread(target=self.__twitterInstantiation)
            stream.start()

            if stream.is_alive():
                print("Thread still running")

        else:
            return Err.ERROR_FLAG_INCORRECT

    except Exception as e:
        return Err.ERROR_JSON_FORMAT_INCORRECT

    return Succ.SUCCESS_TWEETS_STARTED

My code never reaches the line print("Thread still running") because every time it enters the POST request function a new thread is created here stream = Coroutine.Thread(target=self.__twitterInstantiation) and therefore cannot see if the old one is alive.

Can someone please help me here ?

Answer 1

Enumerate alive threads

To get all the alive threads, you can use threading.enumerate().

Thread name

Every Thread can have a custom name. It is obtainable via the name property.

Solution

If you give a thread the name that indicates the job, you can get the thread's name and prevent spawning of the same operation.

if value == "start_live_tweet_streaming":
    for th in threading.enumerate():
        if th.name == job_name:
            print("Thread still running")
            break
    else:
        print("Starting a new job thread")
        stream = Coroutine.Thread(target=self.__twitterInstantiation, name=job_name)
        stream.start()