celery: daemonic processes are not allowed to have children (with concurrent.futures)

Question

In Python (3.6) I try to create processes (with multiprocessing) in a celery task (celery 3.1.17) but it gives the error:

daemonic processes are not allowed to have children

code

def mp():
  with concurrent.futures.ProcessPoolExecutor(max_workers=90) as executor:
                    data = executor.map(pdfocr,[no for no in list(json.keys())])

Answer 1

Start worker with -P threads argument:

celery worker -P threads

Celery version >= 4.4.0 has been officially supported

Refer: https://github.com/celery/celery/issues/4525#issuecomment-566503932