pythonemailflaskwerkzeugflask-mail

Flask-mail send_async_email() generates an exception and RunTimeError: Working outside of application context


The whole thing works except for send_email(). I get the same exception whether I use localhost or remote host. My guess is I am not pushing the context in the right place, but I have been staring at this for a long time and I clearly don't see the error. Any help will be greatly appreciated!

__init__.py:

from flask import Flask, Blueprint, jsonify, ...

from config import config
from flask_login import LoginManager
from extensions import db, mail, moment

login_manager = LoginManager()
login_manager.login_view = 'auth.login'

def create_app():  
    app = Flask(__name__,
                static_url_path='',
                static_folder='../app/static',
                template_folder='../app/templates')

    app.config.from_object(config['default'])
    config['default'].init_app(app)
    
    db.init_app(app)
    mail.init_app(app)
    moment.init_app(app)

    with app.app_context():
        db.create_all()

    migrate = Migrate(app, db)
    from app import models
    
    from .templates.auth import auth_bp
    from .templates.main import main_bp

    app.register_blueprint(main_bp)
    app.register_blueprint(auth_bp, url_prefix='/auth')

    login_manager.init_app(app)

    return app

views.py:

from flask import abort, Blueprint, flash, ...
from flask.globals import current_app
from flask_login import current_user, login_required, login_user, logout_user
from werkzeug.security import generate_password_hash
from datetime import datetime, timezone

from wtforms.validators import UUID

from . import auth_bp

from extensions import db, common_context
from app.models. ...
from .forms import LoginForm, RegistrationForm, ...
from .email import send_email

@auth_bp.route('/register/', methods=['GET', 'POST'], defaults={'user_id': None})
def register(user_id):
    from sqlalchemy.exc import IntegrityError
    from .email import send_email

    if current_user.is_authenticated:
        return redirect(url_for('main.home'))
    form=RegistrationForm()

    if form.validate_on_submit():
        try:
            individual = Individual(...
            )
            db.session.add(individual)
            db.session.flush()

            individual_email = Individual_email(...
            )
            db.session.add(individual_email)

            user = User(...
            )
            db.session.add(user)
            db.session.commit()
            token = user.generate_confirmation_token()
            # with current_app.app_context():
            #     print(individual_email.email, user, individual.first_name, token) - this works!!!
            send_email(individual_email.email, 'Please Confirm Your Account',
                   'auth/email/confirm', user=user, token=token, individual=individual)
            flash('A confirmation email has been sent to you by email.')
        except AssertionError as err:
            db.session.rollback()
            abort(409, err) 
        except IntegrityError as err:
            db.session.rollback()
            abort(409, err.orig) 
        except Exception as err:
            db.session.rollback()
            abort(500, err)
        finally:
            db.session.close()
        return redirect(url_for('auth.login'))
    
    context = {
        'form': form,
        'title': 'Registration',
    }
    return render_template('auth/register.html', **context, **common_context)

email.py:

from flask import render_template, current_app
from flask_mail import Message
from threading import Thread
from app import mail

def send_async_email(app, msg):
    with app.app_context():
        mail.send(msg)

def send_email(to, subject, template, **kwargs):
    app=current_app
    msg = Message(app.config['MAIL_SUBJECT_PREFIX'] + subject, sender = app.config['MAIL_SENDER'], recipients=[to])
    msg.body = render_template(template + '.txt', **kwargs)
    msg.html = render_template(template + '.html', **kwargs)
    thr = Thread(target=send_async_email, args=[app, msg])
    thr.start()
    return thr

Config:

import os

from dotenv import load_dotenv

basedir = os.path.abspath(os.path.dirname(__file__))
load_dotenv(os.path.join(basedir, '.env'))

class Config(object):
    DEBUG = False
    TESTING = False
    CSRF_ENABLED = True

    SECRET_KEY = os.environ.get('SECRET_KEY')
    SQLALCHEMY_TRACK_MODIFICATIONS = False

    ...

    @staticmethod
    def init_app(app):
        pass

class ProductionConfig(Config):
    DEBUG = False
    SQLALCHEMY_DATABASE_URI = os.environ.get('DATABASE_URI')
    MAIL_SERVER = os.environ.get('MAIL_SERVER', 'smtp.gmail.com')
    MAIL_PORT = int(os.environ.get('MAIL_PORT', '587'))
    MAIL_USE_TLS = os.environ.get('MAIL_USE_TLS', 'true').lower() in \
        ['true', 'on', '1']
    MAIL_USE_SSL = os.environ.get('MAIL_USE_SSL', 'false').lower()
    MAIL_USERNAME = os.environ.get('MAIL_USERNAME')
    MAIL_PASSWORD = os.environ.get('MAIL_PASSWORD')
    MAIL_SUBJECT_PREFIX = '[...]'
    MAIL_SENDER = '... <...>'
    MAIL_ADMIN = os.environ.get('MAIL_ADMIN')

class DevelopmentConfig(Config):
    DEVELOPMENT = True
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = os.environ.get('DEV_DATABASE_URI')

    MAIL_SERVER = 'localhost'
    MAIL_PORT = 25
    MAIL_USE_TLS = False
    MAIL_USE_SSL = False
    # MAIL_DEBUG = app.debug
    MAIL_USERNAME = '...'
    MAIL_PASSWORD = os.environ.get('MAIL_PASSWORD')
    MAIL_DEFAULT_SENDER = '... <...>'
    MAIL_MAX_EMAILS = None
    # MAIL_SUPPRESS_SEND = app.testing
    MAIL_ASCII_ATTACHMENTS = False
    MAIL_SUBJECT_PREFIX = '[...]'
    MAIL_SENDER = '... <...>'
    MAIL_ADMIN = '...'

    config = {
    'development': DevelopmentConfig,
    'testing': TestingConfig,
    'production': ProductionConfig,

    'default': DevelopmentConfig
    }

Output:

Exception in thread Thread-23:
Traceback (most recent call last):
  File "C:\...\Python38\lib\threading.py", line 932, in _bootstrap_inner
127.0.0.1 - - [11/Feb/2021 21:04:21] "POST /auth/register/ HTTP/1.1" 302 -
    self.run()
  File "C:\...\Python38\lib\threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "C:\...\app\templates\auth\email.py", line 7, in send_async_email
    with app.app_context():
127.0.0.1 - - [11/Feb/2021 21:04:21] "GET /auth/login HTTP/1.1" 200 -
  File "c:\...\venv\lib\site-packages\werkzeug\local.py", line 347, in __getattr__
    return getattr(self._get_current_object(), name)
  File "c:\...\venv\lib\site-packages\werkzeug\local.py", line 306, in _get_current_object
    return self.__local()
  File "c:\...\venv\lib\site-packages\flask\globals.py", line 52, in _find_app
    raise RuntimeError(_app_ctx_err_msg)
RuntimeError: Working outside of application context.

This typically means that you attempted to use functionality that needed
to interface with the current application object in some way. To solve
this, set up an application context with app.app_context().  See the
documentation for more information.

Solution

  • Combined two functions in email.py into one to avoid context issues:

    def send_email(to, subject, template, **kwargs):
        app=current_app
        with app.app_context():
            msg = Message(app.config['MAIL_SUBJECT_PREFIX'] + subject, sender = 
                  app.config['MAIL_SENDER'], recipients=[to])
            msg.body = render_template(template + '.txt', **kwargs)
            msg.html = render_template(template + '.html', **kwargs)
            Thread(target=mail.send(msg)).start()
    

    It worked fine on the first try. I reviewed other Stackoverflow posts and received advice to import create_app into this module. I advise against that route. I've got either two instances instead of one or the same exception, depending on the placement of create_app() call.