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!

Non-blocking tornado instance on Openshift?

I am trying to create tornado webserver and quick start made me standard project of tornado, but according to documentation this configuration is blocking.
I am new to non-blocking python.
I have this wsgi file that lies in root folder in my PAAS server
#!/usr/bin/env python
import os
import imp
import sys
#
# Below for testing only
#
if __name__ == '__main__':
ip = 'localhost'
port = 8051
zapp = imp.load_source('application', 'wsgi/application')
from wsgiref.simple_server import make_server
httpd = make_server(ip, port, zapp.application)
httpd.serve_forever()
This is main handler file
#!/usr/bin/env python
import tornado.web
class MainHandler(tornado.web.RequestHandler):
def get(self):
self.render('index.html')
And Application folder contains this
# Put here yours handlers.
import tornado.wsgi
from . import handlers
handlers = [(r'/',MainHandler),]
application = tornado.wsgi.WSGIApplication(handlers, **settings)
In WSGI mode asynchronous methods are not supported
uses WSGI to deploy the python applications
Is it possible to configure python application on openshift to be fully non-blocking
Though i have seen project that seemed to work

If you are talking about OpenShift V2 (not V3 which uses Kubernetes/Docker), then you need to use the app.py file as described in:
http://blog.dscpl.com.au/2015/08/running-async-web-applications-under.html

Deploying Watson Visual recognition app fails

I created some custom classifiers locally and then i try to deploy on bluemix an app that classifies an image based on the classifiers i made.
When I try to deploy it, it failes to start.
import os
import json
from os.path import join, dirname
from os import environ
from watson_developer_cloud import VisualRecognitionV3
import time
start_time = time.time()
visual_recognition = VisualRecognitionV3(VisualRecognitionV3.latest_version, api_key='*************')
with open(join(dirname(__file__), './test170.jpg'), 'rb') as image_file:
print(json.dumps(visual_recognition.classify(images_file=image_file,threshold=0, classifier_ids=['Angle_971786581']), indent=2))
print("--- %s seconds ---" % (time.time() - start_time))
Even if I try to deploy a simple print , it failes to deploy, but the starter app i get from bluemix, or a Flask tutorial (https://www.ibm.com/blogs/bluemix/2015/03/simple-hello-world-python-app-using-flask/) i found online deploy just fine.
I'm very new to web programming and using cloud services so i'm totally lost.
Thank you.

Bluemix is expecting your python application to serve on a port. If your application isn't serving some kind of response on the port, it assumes the application failed to start.
# On Bluemix, get the port number from the environment variable PORT
# When running this app on the local machine, default the port to 8080
port = int(os.getenv('PORT', 8080))
#app.route('/')
def hello_world():
return 'Hello World! I am running on port ' + str(port)
if __name__ == '__main__':
app.run(host='0.0.0.0', port=port)
It looks like you're writing your code to just execute once and stop. Instead, make it do the work when someone hits your URL, like shown in the hello_world() function above.
Think about what you want to happen when someone goes to YOUR_APP_NAME.mybluemix.net
If you do not want your application to be a WEB application, but instead just execute once (a background worker application), then use the --no-route option at the end of your cf push command. Then, look at the logs using cf logs appname --recent to see the output of your application
https://console.ng.bluemix.net/docs/manageapps/depapps.html#deployingapps

The main problem was watson-developer-cloud module, giving me an error that it could not be found.
I downgraded to python version 2.7.12, installing it for all users.
Modified runtime.exe and requirments.txt (requirments.txt possible not needed)
Staged with Diego, using no-route and set-health-check APP_NAME none command.
Those fixed the problem, but i still get an exit status 0.

when you deploy an app in bluemix,you should have a requirements.txt which include services you used in your app.
so ,you should checkout your requirements.txt,maybe you lost
watson_developer_cloud
and then, the requirements.txt likes this:
Flask==0.10.1
watson_developer_cloud

Trouble Sending iOS push notifications from Google App Engine

I'm working on my first iOS app that uses push notifications. I have a python script that lets me to send push notifications from my machine but I'm unable to get this working with the Google App Engine Launcher.
When I run this on GAE I get nothing - no errors and no push notifications. What am I doing wrong? I know the code for sending the actual notification is working properly but I'm not able to duplicate this on Google's servers.
Here is the script I'm trying to run with GAE Launcher:
import os
import cgi
import webapp2
from google.appengine.ext.webapp.util import run_wsgi_app
import ssl
import json
import socket
import struct
import binascii
TOKEN = 'my_app_token'
PAYLOAD = {'aps': {'alert':'Push!','sound':'default'}}
class APNStest(webapp2.RequestHandler):
def send_push(token, payload):
# Your certificate file
cert = 'ck.pem'
# APNS development server
apns_address = ('gateway.sandbox.push.apple.com', 2195)
# Use a socket to connect to APNS over SSL
s = socket.socket()
sock = ssl.wrap_socket(s, ssl_version=ssl.PROTOCOL_SSLv3, certfile=cert)
sock.connect(apns_address)
# Generate a notification packet
token = binascii.unhexlify(token)
fmt = '!cH32sH{0:d}s'.format(len(payload))
cmd = '\x00'
message = struct.pack(fmt, cmd, len(token), token, len(payload), payload)
sock.write(message)
sock.close()
send_push(TOKEN, json.dumps(PAYLOAD))
application = webapp2.WSGIApplication([
('/apns', APNStest)
], debug=True)
def main():
run_wsgi_app(application)
if __name__ == "__main__":
main()

So the solution was very simple as I expected. I had enabled billing for the project on cloud.google.com but needed to have billing enabled at appengine.google.com as well. Stupid mistake that set me back 2 days.

Is there any way of detecting an automatic reload in flask's debug mode?

I have a flask app where I'd like to execute some code on the first time the app is run, not on the automatic reloads triggered by the debug mode. Is there any way of detecting when a reload is triggered so that I can do this?
To give an example, I might want to open a web browser every time I run the app from sublime text, but not when I subsequently edit the files, like so:
import webbrowser
if __name__ == '__main__':
webbrowser.open('http://localhost:5000')
app.run(host='localhost', port=5000, debug=True)

You can set an environment variable.
import os
if 'WERKZEUG_LOADED' in os.environ:
print 'Reloading...'
else:
print 'Starting...'
os.environ['WERKZEUG_LOADED']='TRUE'
I still don't know how to persist a reference that survives the reloading, though.

What about using Flask-Script to kick off a process before you start your server? Something like this (cribbed from their documentation and edited slightly):
# run_devserver.py
import webbrowser
from flask.ext.script import Manager
from myapp import app
manager = Manager(app)
if __name__ == "__main__":
webbrowser.open('http://localhost:5000')
manager.run(host='localhost', port=5000, debug=True)

I have a Flask app where it's not really practical to change the DEBUG flag or disable reloading, and the app is spun up in a more complex way than just flask run.
#osa's solution didn't work for me with flask debug on, because it doesn't have enough finesse to pick out the werkzeug watcher process from the worker process that gets reloaded.
I have this code in my main package's __init__.py (the package that defines the flask app). This code is run by another small module which has from <the_package_name> import app followed by app.run(debug=True, host='0.0.0.0', port=5000). Therefore this code is executed before the app starts.
import ptvsd
import os
my_pid = os.getpid()
if os.environ.get('PPID') == str(os.getppid()):
logger.debug('Reloading...')
logger.debug(f"Current process ID: {my_pid}")
try:
port = 5678
ptvsd.enable_attach(address=('0.0.0.0', port))
logger.debug(f'========================== PTVSD waiting on port {port} ==========================')
# ptvsd.wait_for_attach() # Not necessary for my app; YMMV
except Exception as ex:
logger.debug(f'PTVSD raised {ex}')
else:
logger.debug('Starting...')
os.environ['PPID'] = str(my_pid)
logger.debug(f"First process ID: {my_pid}")
NB: note the difference between os.getpid() and os.getppid() (the latter gets the parent process's ID).
I can attach at any point and it works great, even if the app has reloaded already before I attach. I can detach and re-attach. The debugger survives a reload.