Exception running Python Flask app on AWS Elastic Beanstalk

Question

I'm running into an issue trying to run my python web app on EB. It runs fine locally, but I get the following exception when I run it on EB. The problem seems to be that it runs into an exception, but the stack trace is of an error that occurs after that original one, so I can't really determine what the root cause is:

Exception on /admin GET
Traceback (most recent call last):
File "/opt/python/run/venv/lib/python2.7/site-packages/flask/app.py", line 1817, in     wsgi_app
response = self.full_dispatch_request()
File "/opt/python/run/venv/lib/python2.7/site-packages/flask/app.py", line 1477, in     full_dispatch_request
rv = self.handle_user_exception(e)
File "/opt/python/run/venv/lib/python2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/opt/python/run/venv/lib/python2.7/site-packages/flask/app.py", line 1475, in     full_dispatch_request
rv = self.dispatch_request()
File "/opt/python/run/venv/lib/python2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functionshttp://rule.endpoint(**req.view_args)
File "/opt/python/run/venv/lib/python2.7/site-packages/sandman/sandman.py", line 459, in get_collection
cls = endpoint_class(collection)
File "/opt/python/run/venv/lib/python2.7/site-packages/sandman/sandman.py", line 185, in endpoint_class
cls = current_app.class_referencescollection
File "/opt/python/run/venv/lib/python2.7/site-packages/werkzeug/local.py", line 338, in __getattr__
return getattr(self._get_current_object(), name)
AttributeError: 'Flask' object has no attribute 'class_references'

When I manually start the app on port 5000 after SSHing into my instance, and attempted to load the same page from the console, I did not get any error (and the saved file contained the correct HTML):

wget http://127.0.0.1:5000/admin
--2014-03-23 17:01:13-- http://127.0.0.1:5000/admin
Connecting to 127.0.0.1:5000... connected.
HTTP request sent, awaiting response... 127.0.0.1 - - 23/Mar/2014 17:01:13 "GET /admin     HTTP/1.1" 301 -
301 MOVED PERMANENTLY
Location: http://127.0.0.1:5000/admin/ following
--2014-03-23 17:01:13-- http://127.0.0.1:5000/admin/
Connecting to 127.0.0.1:5000... connected.
HTTP request sent, awaiting response... 127.0.0.1 - - 23/Mar/2014 17:01:13 "GET /admin/     HTTP/1.1" 200 -
200 OK
Length: 1519 (1.5K) text/html
Saving to: ‘admin’

this is the python app code I'm running: http://pastebin.com/qgnWz6aK

Answer 1

I managed to work around this issue by using Tornado (though I'm still not sure what the underlying issue is):

from sandman import app
from sandman.model import activate
import logging
import os, sys
from tornado.wsgi import WSGIContainer
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop

app.config['SQLALCHEMY_DATABASE_URI'] = os.environ['DB']

@app.route("/")
def hello():
    return "Hello World!"

if __name__ == "__main__":
    activate(browser=False)
    app.debug = True
    http_server = HTTPServer(WSGIContainer(app))
    http_server.listen(os.environ['PORT'])
    IOLoop.instance().start()