Develop Reference

Deploy a flask app in using Cloudera Application

I have been using the following python 3 script in a CDSW session which run just fine as long as the session is not killed.
I am able to click on the top-right grid and select my app
hello.py
from flask import Flask
import os
app = Flask(__name__)
#app.route('/')
def index():
return 'Web App with Python Flask!'
app.run(host=os.getenv("CDSW_IP_ADDRESS"), port=int(os.getenv('CDSW_PUBLIC_PORT')))
I would like this app to run 24/7, so instead of using a Session or scheduling a job that never ends, I would like to create a CDSW Application so that it doesn't stop.
This is the settings on my application:
Logs:
from flask import Flask
import os
app = Flask(__name__)
#app.route('/')
def index():
return 'Web App with Python Flask!'
app.run(host=os.getenv("CDSW_IP_ADDRESS"), port=int(os.getenv('CDSW_PUBLIC_PORT')))
* Serving Flask app "__main__" (lazy loading)
* Environment: production
WARNING: Do not use the development server in a production environment.
Use a production WSGI server instead.
* Debug mode: off
OSError: [Errno 98] Address already in use
I tried to change the port from CDSW_PUBLIC_PORT to CDSW_APP_PORT but it ends up the same.

As it mentions here maybe you need to change this line of code
app.run(host=os.getenv("CDSW_IP_ADDRESS"), port=int(os.getenv('CDSW_PUBLIC_PORT')))
to this
app.run(host="127.0.0.1", port=int(os.environ['CDSW_APP_PORT']))
Hope it works!

Why does htttp.get give me an Error in Flutter

im trying to get A Value from a Python Script which looks like that:
from flask import Flask, jsonify
app = Flask(__name__)
#app.route('/', methods = ['GET'])
def index():
return jsonify({"greetings" : "Hi this is Python"})
if __name__ == '__main__':
app.run(debug = True)
After launichg im getting the following Output:
C:\Users\finn1\PycharmProjects\FLASK_FLUTTER_APP\venv\Scripts\python.exe C:/Users/finn1/PycharmProjects/FLASK_FLUTTER_APP/main.py
* Serving Flask app "main" (lazy loading)
* Environment: production
WARNING: This is a development server. Do not use it in a production deployment.
Use a production WSGI server instead.
* Debug mode: on
* Restarting with stat
* Debugger is active!
* Debugger PIN: ***-***-***
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
Thei i imported the http libary in Flutter like that :
import 'package:http/http.dart';
Then i tried to get the Data with "http.get":
child: IconButton(
icon: new Icon(
Icons.settings,
),
onPressed: () async {
final response = await http.get("http://127.0.0.1:5000/");
But i am getting the following Error when launching my App:
Error: The getter 'http' isn't defined for the class '_HomepageState'.
- '_HomepageState' is from 'package:what_todo/screens/homepage.dart' ('lib/screens/homepage.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named 'http'.
final response = await http.get("http://127.0.0.1:5000/");
Thank You for Help!

Try to use import 'package:http/http.dart' as http;
package example

Flask app is not destroyed when server exits? [duplicate]

This question already has answers here:
__del__ on exit behavior
(1 answer)
I don't understand this python __del__ behaviour
(8 answers)
Closed 2 years ago.
I have the following, seemingly easy, issue which I cannot figure out.
I made a short, self-containing example below:
from flask import Flask
class MyFlask(Flask):
def __init__(self, name):
super().__init__(name)
print(f'Initialising Flask app {id(self)}')
def __del__(self):
print(f'Deleting Flask app {id(self)}')
if __name__ == "__main__":
app = MyFlask(__name__)
app.run(host='0.0.0.0', port=5000, debug=True)
When one runs this, you will see two instances of MyFlask being initialized, but only one being destroyed. I know why there are two calls to the init method (the way Werkzeug works), but why is only one destroyed?
See the sample output below:
(venv) D:\Onedrive\Documents\Projects\FlaskReloader>python example.py
Initialising Flask app 1944027544880
* Serving Flask app "example" (lazy loading)
* Environment: production
WARNING: This is a development server. Do not use it in a production deployment.
Use a production WSGI server instead.
* Debug mode: on
* Restarting with stat
Initialising Flask app 2213899877680
* Debugger is active!
* Debugger PIN: 247-475-647
* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
Deleting Flask app 1944027544880
Any ideas? Thanks!

I think it cause by the override of Flask.__del__
Call super on that __del__ or don't override
print(f'Deleting Flask app {id(self)}')
super().__del__(self)

How to get arrived timestamp of a request in flask

I have an ordinary Flask application, with just one thread to process requests. There are many requests arriving at the same time. They queue up to wait for be processed. How can I get the waiting time in queue of each request?
from flask import Flask, g
import time
app = Flask(__name__)
#app.before_request()
def before_request():
g.start = time.time()
g.end = None
#app.teardown_request
def teardown_request(exc):
g.end = time.time()
print g.end - g.start
#app.route('/', methods=['POST'])
def serve_run():
pass
if __name__ == '__main__':
app.debug = True
app.run()

There is no way to do that using Flask's debug server in single-threaded mode (which is what your example code uses). That's because by default, the Flask debug server merely inherits from Python's standard HTTPServer, which is single-threaded. (And the underlying call to select.select() does not return a timestamp.)
I just have one thread to process requests.
OK, but would it suffice to spawn multiple threads, but prevent them from doing "real" work in parallel? If so, you might try app.run(..., threaded=True), to allow the requests to start immediately (in their own thread). After the start timestamp is recorded, use a threading.Lock to force the requests to execute serially.
Another option is to use a different WSGI server (not the Flask debug server). I suspect there's a way to achieve what you want using GUnicorn, configured with asynchronous workers in a single thread.

You can doing something like this
from flask import Flask, current_app, jsonify
import time
app = Flask(__name__)
#app.before_request
def before_request():
Flask.custom_profiler = {"start": time.time()}
#app.after_request
def after_request(response):
current_app.custom_profiler["end"] = time.time()
print(current_app.custom_profiler)
print(f"""execution time: {current_app.custom_profiler["end"] - current_app.custom_profiler["start"]}""")
return response
#app.route('/', methods=['GET'])
def main():
return jsonify({
"message": "Hello world"
})
if __name__ == '__main__':
app.run()
And testing like this
→ curl http://localhost:5000
{"message":"Hello world"}
Flask message
→ python main.py
* Serving Flask app "main" (lazy loading)
* Environment: production
WARNING: This is a development server. Do not use it in a production deployment.
Use a production WSGI server instead.
* Debug mode: off
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
{'start': 1622960256.215391, 'end': 1622960256.215549}
execution time: 0.00015807151794433594
127.0.0.1 - - [06/Jun/2021 13:17:36] "GET / HTTP/1.1" 200 -

Flask and uWSGI - unable to load app 0 (mountpoint='') (callable not found or import error)

I get the below error when I try and start Flask using uWSGI.
Here is how I start:
> # cd ..
> root#localhost:# uwsgi --socket 127.0.0.1:6000 --file /path/to/folder/run.py --callable app - -processes 2
Here is my directory structure:
-/path/to/folder/run.py
-|app
-|__init__.py
-|views.py
-|templates
-|static
Contents of /path/to/folder/run.py
if __name__ == '__main__':
from app import app
#app.run(debug = True)
app.run()
Contents of /path/to/folder/app/__init__.py
import os
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
from flask.ext.login import LoginManager
#from flaskext.babel import Babel
from config import basedir
app = Flask(__name__)
app.config.from_object('config')
#app.config.from_pyfile('babel.cfg')
db = SQLAlchemy(app)
login_manager = LoginManager()
login_manager.setup_app(app)
login_manager.login_view = 'login'
login_manager.login_message = u"Please log in to access this page."
from app import views
*** Operational MODE: preforking ***
unable to find "application" callable in file /path/to/folder/run.py
unable to load app 0 (mountpoint='') (callable not found or import error)
*** no app loaded. going in full dynamic mode ***
*** uWSGI is running in multiple interpreter mode ***
spawned uWSGI worker 1 (pid: 26972, cores: 1)
spawned uWSGI worker 2 (pid: 26973, cores: 1)

I had problems with the accepted solution because my flask app was in a variable called app. You can solve that with putting just this in your wsgi:
from module_with_your_flask_app import app as application
So the problem was simply that uwsgi expects a variable called application.

uWSGI doesn't load your app as __main__, so it never will find the app (since that only gets loaded when the app is run as name __main__). Thus, you need to import it outside of the if __name__ == "__main__": block.
Really simple change:
from app import app as application # for example, should be app
if __name__ == "__main__":
application.run()
Now you can run the app directly with python run.py or run it through uWSGI the way you have it.
NOTE: if you set --callable myapp, you'd need to change it from as application to myapp (by default uwsgi expects application

The uWSGI error unable to load app 0 (mountpoint='') (callable not found or import error) occured for me if I left out the last two lines of the following minimal working example for Flask application
from flask import Flask
app = Flask(__name__)
#app.route("/")
def hello():
return "Hello world!"
if __name__ == "__main__":
app.run()
else:
application = app
I am aware that this already implicitly said within the comments to another answer, but it still took me a while to figure that out, so I hope to save others' time.
In the case of a pure Python Dash application, I can offer the following minimal viable code snippet:
import dash
import dash_core_components as dcc
import dash_html_components as html
app = dash.Dash()
app.layout = html.Div( html.H1(children="Hello World") )
application = app.server
if __name__ == "__main__":
app.run_server(debug=True)
Again, the application = app.server is the essential part here.