Job is not performed by APScheduler's BackgroundScheduler

Question

I have a Django application that I'm running on Docker. I'm trying to launch an APScheduler scheduler when I run the docker container.

I created a scheduler and I simply added it a job that I called test1, and that sends an email to my address.

This is the Python script that is launched when I run the container.

from apscheduler.schedulers.blocking import BlockingScheduler
from apscheduler.schedulers.background import BackgroundScheduler

#scheduler = BlockingScheduler()
scheduler = BackgroundScheduler()

def test1():
    ... (code to send email)

scheduler.add_job(test1, 'interval', seconds = 20)
scheduler.start()

This is the results I obtained with each of the two kind of schedulers:

• BlockingScheduler: the scheduler works, I receive an email every 20 seconds. However I can't access the app. I presume this is normal due to the very nature of the BlockingScheduler.

screenshot1

screenshot2

• BackgroundScheduler: no problem to access the application. However, I receive no email.

Since the emails were sent in one of the two cases I guess the problem is neither Django nor Docker related, but purely about APScheduler. I did my research but I couldn't find why the BackgroundScheduler didn't work as in the tutorials I read, the developper set up the scheduler the same way I did.

Any help would be much appreciated, thanks!

UPDATE 1

I tried the two following things, both made the BackgroundScheduler behave like a BlockingScheduler (which is not what I want)

1) Setting the daemon option to False when initialising the scheduler instance:

scheduler = BackgroundScheduler(daemon = False)

2) "Trying to keep the main thread alive", as explained in these:

how-do-i-schedule-an-interval-job-with-apscheduler

apscheduler-inside-a-class-object

I added this right after scheduler.starts():

while True:
    time.sleep(1)
scheduler.shutdown()

UPDATE 2

When I try to setup a BackgroundScheduler in a single Python file (outside of any application context), it works very well:

from apscheduler.schedulers.background import BackgroundScheduler
from apscheduler.schedulers.blocking import BlockingScheduler


def test1():
    print('issou')

scheduler = BackgroundScheduler()
scheduler.start()
scheduler.add_job(test1, 'interval', seconds=5)

print('yatangaki')

'yatangaki' is first printed, and then 'issou' every 5 seconds, so everything seems fine.

UPDATE 3

Now I've tried to start the scheduler on a Django app that I ran locally with python manage.py runserver, without using Docker.

It works perfectly: the emails are sent and I can access the main view of the application.

Note: the BackgroundScheduler is started by a function called start_test1. In this app, I run start_test1 in the top-level urls.py file. On the other app - the one that I run with Docker, which is the one I want to use in the end - start_test1 is started in a Python script, that is itself triggered in a .sh file, which I run via the CMD Docker command.

Alliteration

"However I can't access the app" what did you mean by this? – Kinna

I mean when I go to localhost:8000, I get "This site can't be reached, localhost refused to connect", which is not the case when I use the BackgroundScheduler. I'm going to add a screenshot to my post to make it clearer – Alliteration

do you see anything else in the terminal console, where you did the manage.py runserver? – Kinna

Oh I see your screenshot, in the first screenshot you have a wrong url, which should be: localhost:8000 instead of localhost8000.com I guess – Kinna

How do you send email? – Meteoric

screenshot1 was wrong, I just edited it. What I get is actually "localhost didn't send any data" – Alliteration

BackgroundScheduler use a threadpool as executor, so maybe the problem is about threading. – Meteoric

I send the emails thanks to the smtplib library. Works very well in the case of BlockingScheduler – Alliteration

Answer 1

It appears it was all about where to start the scheduler and to add the job.

In what I did initially (putting the code in a .sh file), the BackgroundScheduler started but the Python script immediately ended after being ran, as it didn't have a blocking behaviour and the sh. file wasn't really part of the app (it's used by the Dockerfile, not by the app).

I ended up finding the solution here: execute-code-when-django-starts-once-only There was no apps.py file inside my application so I created one and followed the instruction in this thread.

It works fine now.

Alliteration

I also have this problem, I put the apscheduler start function in urls.py, but the job still stop working after a while. – Antennule

Answer 2

I have a similar problem but it got solved only by not blocking the worker:

# working:
def worker():

    phone_elm = ....
    thread = threading.Thread(target=work, args=(phone_elm,))
    thread.start()

# not working:
def worker():
    phone_elm = ....
    work(phone_elm)

scheduler2 = BackgroundScheduler(timezone="Asia/Kolkata")
# schedule scanning running of folder's running file
scheduler2.add_job(worker, 'interval', seconds=15,  max_instances=5000)

scheduler1.start()

I mean the not working, is that after 10 ~ time it triggered it was stopped for no reason, started again after 1 of the 10 stopped (work exited)

It is also part of Django, but it is clear that start is not exiting...

Godred