Flask - 运行时错误：找不到应用程序。 在视图函数内工作或推送应用程序上下文

Question

I'm now trying to make an application that processes HTTP requests with REST APIs. The application uses Flask for the web framework, and it uses Celery for the asynchronous tasks.

Here's the application structure.

app.py
celery_app.py
controller/
    controller.py
task/
    task.py

(1) app.py

There are no lines for the Celery configuration.

from flask import Flask
...

app = Flask(__name__)
...


if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000, debug=True)

(2) celery.py

from consts.consts import Consts
from kombu.utils.url import quote
from celery import Celery
from config.config import Config

config = Config()
db_uri = 'db+' + config.get_db_uri()

aws_access_key = quote(config.get_config(Consts.AWS, Consts.AWS_ACCESS_KEY))
aws_secret_key = quote(config.get_config(Consts.AWS, Consts.AWS_SECRET_KEY))
broker_url = "sqs://{aws_access_key}:{aws_secret_key}@".format(
    aws_access_key=aws_access_key, aws_secret_key=aws_secret_key
)

celery = Celery(
    broker=broker_url,
    backend=db_uri,
    include=['task']
)

(3) task/task.py

I put all the tasks here.

from celery_app import celery
from flask import current_app as app
from model.model import db


@celery.task
def check_friend_status_from_db(user1, user2):
    status = db.engine.execute(
            "QUERY").fetchone()
    return status

Now, the controller/controller.py file imports and calls the tasks as follows.

(4) controller/controller.py

from flask import Blueprint, request, json, render_template, jsonify
from mysql.connector import Error
from sqlalchemy import or_, and_
from consts.consts import StatusCode
from consts.consts import Consts
from model.model import db, FriendRequest
from outbound.request import Request
from util.logging import logger
from task.task import check_friend_status_from_db


controller_blueprint = Blueprint('controller_blueprint', __name__)
outbound_request = Request()


@controller_blueprint.route('/friend/status/<requested_from>/<requested_to>', methods=['GET'])
def check_friend_status(requested_from, requested_to):
    logger.info('Checking the friend status')
    try:
        status = check_friend_status_from_db.apply_async((requested_from, requested_to)).get()

        if status is None:
            response = {
                Consts.STATUS_CODE: StatusCode.OK,
                Consts.FRIEND_STATUS: StatusCode.NO_RELATION
            }
        else:
            response = {
                Consts.STATUS_CODE: StatusCode.OK,
                Consts.FRIEND_STATUS: status
            }
    except Error as e:
        logger.error("TypeError:", e)
        response = {
            Consts.STATUS_CODE: StatusCode.ERROR
        }
    json_response = jsonify(response)
    logger.info(json_response)
    return json_response

When I run the code, I get the error as I mentioned on the title.

RuntimeError: No application found. Either work inside a view function or push an application context

and it turns out to be this part under the try block in the controller where the error is coming from.

status = check_friend_status_from_db.apply_async((requested_from, requested_to)).get()

Any solutions, please?

Answer 1

It looks like you need to register your blueprint controller_blueprint . Since this blueprint is not registered to your app , you are working outside the context of you application and hence the error.

You can do so in your app.py:

from controller.controller import controller_blueprint

app = Flask(__name__)
app.register_blueprint(controller_blueprint)