How to perform periodic task with Flask in Python

Question

I\'ve been using Flask to provide a simple web API for my k8055 USB interface board; fairly standard getters and putters, and Flask really made my life a lot easier.

<

Answer 1

For my Flask application, I contemplated using the cron approach described by Pashka in his answer, the schedule library, and APScheduler.

I found APScheduler to be simple and serving the periodic task run purpose, so went ahead with APScheduler.

Example code:

from flask import Flask

from apscheduler.schedulers.background import BackgroundScheduler


app = Flask(__name__)

def test_job():
    print('I am working...')

scheduler = BackgroundScheduler()
job = scheduler.add_job(test_job, 'interval', minutes=1)
scheduler.start()

Answer 2

You could use cron for simple tasks.

Create a flask view for your task.

# a separate view for periodic task
@app.route('/task')
def task():
    board.read()
    board.digital_outputs = board.digital_inputs

Then using cron, download from that url periodically

# cron task to run each minute
0-59 * * * * run_task.sh

Where run_task.sh contents are

wget http://localhost/task

Cron is unable to run more frequently than once a minute. If you need higher frequency, (say, each 5 seconds = 12 times per minute), you must do it in tun_task.sh in the following way

# loop 12 times with a delay
for i in 1 2 3 4 5 6 7 8 9 10 11 12
do
    # download url in background for not to affect delay interval much
    wget -b http://localhost/task
    sleep 5s
done

Answer 3

No there is not tasks support in Flask, but you can use flask-celery or simply run your function in separate thread(greenlet).