flask application with background threads

Try this example, tested on Python 3.4.3 / Flask 0.11.1

from flask import Flaskfrom time import sleepfrom concurrent.futures import ThreadPoolExecutor# DOCS https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.ThreadPoolExecutorexecutor = ThreadPoolExecutor(2)app = Flask(__name__)@app.route('/jobs')def run_jobs():    executor.submit(some_long_task1)    executor.submit(some_long_task2, 'hello', 123)    return 'Two jobs were launched in background!'def some_long_task1():    print("Task #1 started!")    sleep(10)    print("Task #1 is done!")def some_long_task2(arg1, arg2):    print("Task #2 started with args: %s %s!" % (arg1, arg2))    sleep(5)    print("Task #2 is done!")if __name__ == '__main__':    app.run()

Check out Flask-Executor which uses concurrent.futures in the background and makes your life very easy.

from flask_executor import Executorexecutor = Executor(app)@app.route('/someJob')def index():    executor.submit(long_running_job)    return 'Scheduled a job'def long_running_job    #some long running processing here

This not only runs jobs in the background but gives them access to the app context. It also provides a way to store jobs so users can check back in to get statuses.

The best thing to do for stuff like this is use a message broker. There is some excellent software in the python world meant for doing just this:

• Celery (http://www.celeryproject.org/), and
• RQ (http://python-rq.org/).

Both are excellent choices.

It's almost never a good idea to spawn a thread the way you're doing it, as this can cause issues processing incoming requests, among other things.

If you take a look at the celery or RQ getting started guides, they'll walk you through doing this the proper way!