[PLS HELP] Flask-Appbuilder - accessing scheduler from views.py

[palkoc]

Hi all,
I would like to ask you for a help. I have a Flask application (based on flask-appbuilder). The scheduler is initialized and started in __init__.py:

..
# Create application, instance of flask-appbuilder
app.config['APP_NAME'] = app.config['APP_NAME']+" "+'.'.join(map(str,app.config['VERSION']))

db = SQLA(app)
migrate = Migrate(app, db)

appbuilder = AppBuilder(app, db.session, indexview=MyIndexView, base_template="mybase.html", security_manager_class=MySecurityManager, menu=Menu(extra_classes="navbar-fixed-top "))
from . import models, views, ap

...
# Task function for the scheduler
def collect_master(master_hostname=None):
    with app.app_context():
        logging.debug(f'Master {master_hostname} collection in progress')
        nbkt_check_api.get_master_events(master_name=master_hostname, internal=True)
        logging.debug('------------------------------------------------------')

# initialize scheduler
scheduler = APScheduler()
# if you don't wanna use a config, you can set options here:
# scheduler.api_enabled = True
scheduler.init_app(app)
scheduler.start()
...

# Create scheduler..
if app.config['SCHEDULER_DEFAULT_COLLECTION_INTERVAL'] >0:
    for master in active_masters:
        logging.debug(f"Starting scheduled job for: {master.hostname}, default collection interval: {app.config['SCHEDULER_DEFAULT_COLLECTION_INTERVAL']}")

        job = scheduler.add_job(
                trigger = 'interval', 
                id=f"{master.hostname}", 
                name = f"{master.hostname}", 
                seconds=app.config['SCHEDULER_DEFAULT_COLLECTION_INTERVAL'], 
                misfire_grace_time=900,
                replace_existing=True,
                func = collect_master,
                args = [master.hostname],
        )
        scheduled_jobs.append(job)

I have views.py where the data views are defined. There is a post_update method invoked when a model data are modified. I would like to add/remove/modify a scheduler task based on model changes - using scheduler.add_job,scheduler.remove_job

Here's a snippet from views.py

...
# I have updated a data model and I need to delete the scheduled job here

def post_update(self, item):
    super()
    logging.debug(f"Master server has been deactivated: [{item}]")
    logging.debug(f"Stopping scheduled collection")
    
    # Here I don't know how to access the scheduler created in __init__.py. ...
    scheduler.delete_job(item) # How to access it?
...

My question is: How to access the scheduler created in __init__.py from within views.py?

Thanks a lot.
Pavol

[christopherpickering]

I do something similar.. here's how I'm doing it:

1. file called extensions.py where scheduler is initialized.. an also sqlachemy if you are using it.

from flask_apscheduler import APScheduler
from flask_sqlalchemy import SQLAlchemy # optional for sqlalchemy
from flask_sqlalchemy_caching import CachingQuery  # for sqlalchemy

db = SQLAlchemy(query_class=CachingQuery)  # for sqlalchemy
atlas_scheduler = APScheduler()

2. then in __init__.py you can import it.

from scheduler.extensions import atlas_scheduler, db

...
# set it up inside you create_app()

db.init_app(app)

 with app.app_context():
        # pylint: disable=W0611
        if atlas_scheduler.running is False:
            # pytest imports twice. this will save us on the
            # second import.
            atlas_scheduler.start()
     # here you should also add event listeners if you want them.

you can now import the scheduler from the extensions.py wherever you want to use it. You will probably need to wrap w/ an app_context to make everything work.

Here's a link to my project: https://github.com/atlas-bi/atlas-automation-hub/tree/main/scheduler

[palkoc]

Hi @christopherpickering
Thanks a lot for your hint. It's helped and now the code is working fine! Here's my version:

extenstions.py:

from flask_apscheduler import APScheduler
from flask_apscheduler.auth import HTTPBasicAuth
import logging
from .. import api

def collect_master(master_hostname=None):
    nbkt_check_api = api.NetbackupCheckApi()
    logging.debug(f'Master {master_hostname} collection in progress')
    nbkt_check_api.get_master_events(master_name=master_hostname, internal=True)
    logging.debug('------------------------------------------------------')

scheduler = APScheduler()
scheduler.api_enabled = True
scheduler.auth = HTTPBasicAuth() 

@scheduler.authenticate
def authenticate(auth):
    """Check auth."""
    return auth["username"] == "guest" and auth["password"] == "guest"

Initializing from __init___.py:

...

app = Flask(__name__)
app.config.from_object("config")

app.config['APP_NAME'] = app.config['APP_NAME']+" "+'.'.join(map(str,app.config['VERSION']))

db = SQLA(app)
migrate = Migrate(app, db)

appbuilder = AppBuilder(app, db.session, indexview=MyIndexView, base_template="mybase.html", security_manager_class=MySecurityManager, menu=Menu(extra_classes="navbar-fixed-top "))
from . import models, views, api# noqa
from .scheduler.extensions import scheduler, collect_master
scheduler.start()
# Add tasks to collect data from active masters
active_masters = db.session.query(models.MasterServer).filter_by(active=true()).all()
if active_masters is not None:
    logging.debug(f"Active masters found: {active_masters}")
    if app.config['SCHEDULER_DEFAULT_COLLECTION_INTERVAL'] >0:
        for master in active_masters:
            logging.debug(f"Starting scheduled job for: {master.hostname}, default collection interval: {app.config['SCHEDULER_DEFAULT_COLLECTION_INTERVAL']}")
            with app.app_context():
                job = scheduler.add_job(
                        trigger = 'interval', 
                        id=f"{master.hostname}", 
                        name = f"{master.hostname}", 
                        seconds=app.config['SCHEDULER_DEFAULT_COLLECTION_INTERVAL'], 
                        misfire_grace_time=900,
                        replace_existing=True,
                        func = collect_master,
                        args = [master.hostname],
                )

And finally views.py:

...
from .scheduler.extensions import scheduler, collect_master
...
    def post_update(self, item):
        super()
        logging.debug(f"Currently scheduled jobs: [{scheduler.get_jobs()}]")
        logging.debug(f"Is current item scheduled? [{scheduler.get_job(item.hostname)}]")
        if not item.active and scheduler.get_job(item.hostname):
            logging.debug(f"Master {item} is not active anymore, removing if from the scheduler")
            scheduler.remove_job(item.hostname)
            logging.debug(f"Currently scheduled jobs: [{scheduler.get_jobs()}]")
        if item.active and  scheduler.get_job(item.hostname) is None:
            logging.debug(f"Master {item} is active now, adding it to the scheduler")
            scheduler.add_job(
                    trigger = 'interval', 
                    id=f"{item.hostname}", 
                    name = f"{item.hostname}", 
                    seconds=appbuilder.app.config['SCHEDULER_DEFAULT_COLLECTION_INTERVAL'], 
                    misfire_grace_time=900,
                    replace_existing=True,
                    func = collect_master,
                    args = [item.hostname],
            )
            logging.debug(f"Currently scheduled jobs: [{scheduler.get_jobs()}]")

Thanks again and Happy New year :)