CODEWITHSUNDEEP
pythonflasksqlalchemyceleryflask-sqlalchemy
Anconia
Anconia

Reputation: 4038

Celery with Flask and Flask-SQLAlchemy cannot update a database record

I'm creating a background celery task with Flask and Flask-SQLAlchemy to update a property of a database record. I am using the recommended documentation for the celery config and this is a simplified version of my code:

from flask import Flask
from celery import Celery

def make_celery(app):
    celery = Celery(app.import_name, broker=app.config['CELERY_BROKER_URL'])
    celery.conf.update(app.config)
    TaskBase = celery.Task
    class ContextTask(TaskBase):
        abstract = True
        def __call__(self, *args, **kwargs):
            with app.app_context():
                return TaskBase.__call__(self, *args, **kwargs)
    celery.Task = ContextTask
    return celery


app = Flask(__name__)

celery = make_celery(app)

class Stuff(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    processed = db.Column(db.Boolean)


@celery.task()
def process_stuff(stuff_id):
    stuff = Stuff.query.get(stuff_id)
    print("stuff.processed 1: {}".format(stuff.processed))
    stuff.processed = True
    print("stuff.processed 2: {}".format(stuff.processed))
    db.session.add(stuff)
    db.session.commit()
    print("stuff.processed 3: {}".format(stuff.processed))

@app.route("/process_stuff/<id>")
def do_process_stuff(id):
    stuff = Stuff.query.get_or_404(id)
    process_stuff.delay(stuff.id)
    return redirect(url_for("now_wait"))

And this is the output from the print statements:

[2017-07-11 07:32:01,281: WARNING/PoolWorker-4] stuff.processed 1: False
[2017-07-11 07:32:01,282: WARNING/PoolWorker-4] stuff.processed 2: False
[2017-07-11 07:32:01,285: WARNING/PoolWorker-4] stuff.processed 3: False

I can see in my celery worker logs that the task is being picked up and completed; however, the print statements show that the stuff.processed property is ALWAYS False - the print statement never shows True even after I update it manually (I've tested this outside of celery and I can update the property just fine).

There is a very similar problem here but that solution did not work for my situation

Library Versions

Update

Additional testing shows I can create and persist newly created objects to the database - updating pre-existing objects continues to fail.

Upvotes: 4

Views: 2537

Answers (1)

Anconia
Anconia

Reputation: 4038

In my question, I simplified the code substantially and when doing so I changed the reserved property to processed. My actual model looks more like this:

class Stuff(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    reserved = db.Column(db.Boolean)

It turns out that reserved is a function in celery, which is why the property could not be updated from my celery task. The solution was to rename the reserved property on the model.

Upvotes: 1

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