I have the following situation :
config.py
SQLALCHEMY_DATABASE_URI = 'postgresql://a:a#localhost/a'
SQLALCHEMY_POOL_SIZE = 5
SQLALCHEMY_TRACK_MODIFICATIONS = True
models.py
class account_map(db.Model):
__tablename__ = 'account_map'
account_id = db.Column(db.Integer, primary_key=True)
account_key_type = db.Column(db.Text, nullable=False)
account_key_value = db.Column(db.Text, nullable=False)
app.py
from flask import Flask, jsonify
from flask_sqlalchemy import SQLAlchemy
import models
app = Flask(__name__)
app.config.from_pyfile('config.py')
db = SQLAlchemy(app)
#app.route('/account/<int:account_id>', methods=['GET'])
def get_account(account_id):
account = models.account_map.query.get(account_id)
if account:
return jsonify(account.as_dict())
return jsonify(error=404, message=str("Not found"), timestamp=datetime.timestamp(datetime.utcnow())), 404
if __name__ == '__main__':
app.run()
To check how many connections are opened:
SELECT * FROM pg_stat_activity where datname = '...';
No matter how many requests are performed ( I've used JMeter with 25 concurrent users ) there is just only one connection in the database opened, and the Throughput is almost the same as like I'm using just one thread.
Update
I have found out why i don't see many connection is Postgresql : Flask is single threaded by default. It is needed to specify
threaded = True
when you start the application. SQLAlchemy connection pooling is working.
Related
I have this code that is trying to connect to a user table in a database:
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
import yaml
db_info = yaml.safe_load(open('db.yaml'))
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'mssql+pyodbc://{dbuser}:{dbpass}#{server}.database.windows.net/{' \
'dbname}?driver=ODBC+Driver+17+for+SQL+Server'.format(
dbuser=db_info['user'],
dbpass=db_info['password'],
server=db_info['server'],
dbname=db_info['name']
)
db = SQLAlchemy(app)
class Users(db.Model):
ID = db.Column(db.Integer, primary_key=True, nullable=False)
UserName = db.Column(db.Text)
PhoneNum = db.Column(db.Text)
Password = db.Column(db.Text)
YearOfStudy = db.Column(db.Integer)
def __repr__(self):
return '<User %r>' % self.ID
#app.route('/')
def hello_world(): # put application's code here
print(Users.query.all())
return "Hello World"
if __name__ == '__main__':
app.run()
However when I run it, the link generated by the flask application doesn't load and the program terminates from timing out.
I did some debugging and saw that Users.query call results in an error as such:
Working outside of application context.
This typically means that you attempted to use functionality that needed
the current application. To solve this, set up an application context
with app.app_context(). See the documentation for more information.
I tried using with app.app_context to run the program by using code as such:
def __repr__(self):
return '<User %r>' % self.username
if __name__ == '__main__':
with app.app_context():
print(User.query.all())
But it didn't work. I also tried doing this:
db = SQLAlchemy()
def create_app():
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'mssql+pyodbc://{dbuser}:{dbpass}#{server}.database.windows.net/{' \
'dbname}?driver=ODBC+Driver+17+for+SQL+Server'.format(
dbuser=db_info['user'],
dbpass=db_info['password'],
server=db_info['server'],
dbname=db_info['name']
)
db.init_app(app)
return app
app = create_app()
...
...
if __name__ == '__main__':
app.run()
Which had moderate success but the queries for User.query.all() still don't show, and filter_by() functions don't work either.
I also cannot use db.create_all() as this is a ready database, so I can't wipe the database I'm working on
I have been trying to solve an issue related to SQLALCHEMY in Flask as my db is not getting created even though I set the SQLACHEMY_DATABASE_URI to "app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db'".
In the warning it says the 'sqlite:///:memory:'. When db.create_all() is call test.sql file is not created and also in the UI I see errors as mentioned bellow:
Instance of 'SQLAlchemy' has no 'Column' memberpylint(no-member) and 3 others
Please help in resolving this issue and generating the db and SQL file.
from flask import Flask, render_template, url_for
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime
#Initializing database
app = Flask(__name__)
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db'
db = SQLAlchemy(app)
#Creating model
class Todo(db.Model):
id = db.Column(db.Integer, primary_key=True)
content = db.Column(db.String(200), nullable=False)
completed = db.Column(db.Integer, default=0)
date_created = db.Column(db.DateTime, default=datetime.utcnow)
def __repr__(self):
return '<Task %r>' % self.id
app = Flask(__name__)
#app.route('/')
def index():
return render_template('index.html')
if __name__ == "__main__":
app.run(debug=True)
First of all, I have tried looking for answers in this website. But no luck...
What I wanna achieve is that starting an independent thread in the request handling thread to do some asynchronous task. The tricky point is that there are some database operations needed in this independent thread.
Here is an example. Five files included.
project
|__manager.py
|__config.py
|__deployer
|__`__init__.py`
|__models.py
|__views.py
|__operators.py
Detail code below...
# deployer/__init__.py
from flask import Flask
from deployer.models import db
def create_app():
app = Flask(__name__)
app.config.from_object(object_name)
db.init_app(app)
# Add route for index
#app.route('/')
def index():
return {'code': 200, 'message': 'OK'}
return app
# manager.py
from os import environ
from flask_script import Manager, Server
from deployer import create_app
from flask_restful import Api
from deployer.views import HostView
env = environ.get('APM_ENV', 'dev')
app = create_app('config.%sConfig' % env.capitalize())
api = Api(app)
api.add_resource(HostView, '/api/v1/hosts')
manager = Manager(app)
manager.add_command("server", Server(host='0.0.0.0', port=9527))
if __name__ == '__main__':
manager.run(default_command='server')
# deployer/views.py
from flask_restful import Resource, reqparse
from flask import jsonify
from deployer.models import db, Host
from deployer.operators import HostInitiator
parser = reqparse.RequestParser()
parser.add_argument('host', type=int, help='Specify an unique host.')
class HostView(Resource):
def get(self):
h = db.session.query(Host).filter(Host.id == 1).one()
return jsonify(
host_id=h.id,
host_code=h.code,
host_ip=h.ip_addr_v4
)
def post(self):
h = Host(
code='Harbor',
ip_addr_v4='10.10.10.199',
state='created'
)
db.session.add(h)
db.session.commit()
initiator = HostInitiator(host=h)
initiator.start()
return {
'code': 'Harbor',
'ip_addr_v4': '10.10.10.199',
'state': 'created'
}
# deployer/models.py
from sqlalchemy import Column, Integer, String
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
class Host(db.Model):
__tablename__ = 'br_host'
id = Column(Integer, primary_key=True, autoincrement=True)
code = Column(String(128), index=True, nullable=False)
ip_addr_v4 = Column(String(15), nullable=False)
state = Column(String(16), nullable=False)
# deployer/operators.py
from threading import Thread
from deployer.models import db
class HostInitiator(Thread):
def __init__(self, host):
super().__init__()
self.host = host
def run(self):
# Update Host.state [created-->initating]
db.session.query(Host).filter(Host.id == self.host.id).update({'state': 'initating'})
db.session.commit()
# do some initiating things...
# Update Host.state [initating-->ready]
db.session.query(Host).filter(Host.id == self.host.id).update({'state': 'ready'})
db.session.commit()
Always got outside application context error with code above. The error message indicates that no database operation is permitted in the HostInitiator thread.
It suggests me to push a context or move my code into a view function. I'm suffering this quite a while, please help out if you guys have any suggestions. Thanks in advance.
The code works for me
def test_multi_threading_query():
# module which i create Flask app instance
from app.main import app
# module which i create sqlalchemhy instance
from app.model.db import db, Post
with app.app_context():
posts = Post.query.all()
p = posts[0]
p.foo = 1
db.session.add(p)
db.session.commit()
print(p)
#api.route('/test')
def test_view():
from threading import Thread
t = Thread(target=test_multi_threading_query)
t.start()
return ''
# main.py
app = Flask(__main__)
#db.py
db = SQLAlchemy()
class Post(db.Model):
id = db.Column(db.Integer, primary_key=True)
foo = db.Column(db.Integer)
https://flask.palletsprojects.com/en/1.1.x/appcontext/
I've read many of the other posts on having models separated from the main app but I can't get it to work with just app.py (my actual app) and models.py (my database models).
If I do the following I get an app.db file with no tables:
from app import db
db.create_all()
If I do the following I get a RuntimeError: No application found. Either work inside a view function or push an application context.:
from app import db
db.create_all()
I have also looked at Introduction into Contexts page and can't work out where I put def create_app():, none of it seemed to work in my case.
Here is my app.py:
from flask import Flask, render_template, request
from flask_sqlalchemy import SQLAlchemy
from models import userTable
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)
#app.route('/', methods=['GET', 'POST'])
def home():
return "home"
if __name__ == '__main__':
app.run(debug=True)
Here is my models.py:
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
class userTable(db.Model):
__tablename__ = "userTable"
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True)
Perhaps you could try the following:
app.py
from flask import Flask, render_template, request
from flask_sqlalchemy import SQLAlchemy
import models
from models import initialize_db
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
initialize_db(app)
#app.route('/', methods=['GET', 'POST'])
def home():
return "home"
if __name__ == '__main__':
app.run(debug=True)
models.py
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
def initialize_db(app):
app.app_context().push()
db.init_app(app)
db.create_all()
class userTable(db.Model):
__tablename__ = "userTable"
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True)
The key is creating a database initialization function within models.py which takes the application instance as a parameter. This function only creates the database tables once it has its application instance. This will allow you to import the models module initially without an application instance and still have a modular design.
Ello ello,
I found similar questions on the bug i'm facing, and tried the solutions offered but it didn't work for me.
I'm trying to separate out my models in a different directory and import them into the app.py
When I try to import the db into the python terminal, i'm getting the no application found.
app.py code
from flask import Flask
from flask_restful import Resource, Api
# from flask_sqlalchemy import SQLAlchemy
from routes import test, root, user
from models.todo import db
app = Flask(__name__)
api = Api(app)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://username:pass123#localhost/db'
app.config['SECRET_KEY'] = 'thiskeyissecret'
# db.init_app(app)
with app.app_context():
api = Api(app)
db.init_app(app)
api.add_resource(root.HelloWorld, '/')
api.add_resource(test.Test, '/test')
api.add_resource(user.User, '/user')
if __name__ == '__main__':
app.run(debug=True)
models
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
class Todo(db.Model):
__tablename__ = 'Todos'
id = db.Column('id', db.Integer, primary_key=True)
data = db.Column('data', db.Unicode)
def __init__(self, id, data):
self.id = id
self.data = data
def __repr__(self):
return '<Todo %>' % self.id
my file directory looks like
Main_app
Models
Todo.py
routes
some routes
app.py
Flask-SQLAlchemy needs an active application context.
Try:
with app.app_context():
print(Todo.query.count())
From the flask documentation:
Purpose of the Context
The Flask application object has attributes, such as config, that are
useful to access within views and CLI commands. However, importing the
app instance within the modules in your project is prone to circular
import issues. When using the app factory pattern or writing reusable
blueprints or extensions there won’t be an app instance to import at
all.
Flask solves this issue with the application context. Rather than
referring to an app directly, you use the the current_app proxy, which
points to the application handling the current activity.
Flask automatically pushes an application context when handling a
request. View functions, error handlers, and other functions that run
during a request will have access to current_app.
It is ok to have db initialised in app.py
from flask import Flask
from flask_restful import Api
from flask_sqlalchemy import SQLAlchemy
from routes import test, root, user
app = Flask(__name__)
api = Api(app)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://username:pass123#localhost/db'
app.config['SECRET_KEY'] = 'thiskeyissecret'
db = SQLAlchemy(app)
api.add_resource(root.HelloWorld, '/')
api.add_resource(test.Test, '/test')
api.add_resource(user.User, '/user')
if __name__ == '__main__':
app.run(debug=True)
Then in your todo.py
from app import db
class Todo(db.Model):
__tablename__ = 'Todos'
id = db.Column('id', db.Integer, primary_key=True)
data = db.Column('data', db.Unicode)
def __init__(self, id, data):
self.id = id
self.data = data
def __repr__(self):
return '<Todo %>' % self.id
I get a same err
that err reason for just can operation db in viewfunc
def __init__(self, id, data):
self.id = id
self.data = data
try move that code operation to your viewfunc
In a nutshell, do something like this:
from yourapp import create_app
app = create_app()
app.app_context().push()