Long running script from flask endpoint

I've been pulling my hair out trying to figure this one out, hoping someone else has already encountered this and knows how to solve it :)

I'm trying to build a very simple Flask endpoint that just needs to call a long running, blocking php script (think while true {...}). I've tried a few different methods to async launch the script, but the problem is my browser never actually receives the response back, even though the code for generating the response after running the script is executed.

I've tried using both multiprocessing and threading, neither seem to work:

# multiprocessing attempt
@app.route('/endpoint')
def endpoint():
  def worker():
    subprocess.Popen('nohup php script.php &', shell=True, preexec_fn=os.setpgrp)

  p = multiprocessing.Process(target=worker)
  print '111111'
  p.start()
  print '222222'
  return json.dumps({
    'success': True
  })

# threading attempt
@app.route('/endpoint')
def endpoint():
  def thread_func():
    subprocess.Popen('nohup php script.php &', shell=True, preexec_fn=os.setpgrp)

  t = threading.Thread(target=thread_func)
  print '111111'
  t.start()
  print '222222'
  return json.dumps({
    'success': True
  })

In both scenarios I see the 111111 and 222222, yet my browser still hangs on the response from the endpoint. I've tried p.daemon = True for the process, as well as p.terminate() but no luck. I had hoped launching a script with nohup in a different shell and separate processs/thread would just work, but somehow Flask or uWSGI is impacted by it.

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