Failing on create_engine while using SQLAlchemy on ElasticBeanstalk - python-2.7

Question

I am attempting to deploy a Flask application which uses SQLAlchemy to an AWS ElasticBeanstalk environment. I can deploy and see a running application, but when I attempt to use create_engine to connect to my database the whole thing crashes. I can run the run the whole app locally on a linux vm (including using the database within the ElasticBeanstalk environment.) I can ssh into the app server and print to the terminal.
I think something about how the application runs when being accessed from a browser (via the application url) is causing the problem. I would be immensely grateful if someone can point me in the right direction. I've been working on this problem for 3 days and I'm starting to go nuts.
This is the code I am using to create my session:
from sqlalchemy import create_engine, Column, ForeignKey, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, sessionmaker
from sqlalchemy.engine.url import URL
import settings
Base = declarative_base()
# establish connection to database
def db_connect():
"""
Performs database connection using database settings from settings.py.
Returns sqlalchemy engine instance
"""
print ".............................................."
print "...Connecting to Database at URL : "
print "...attempting URL(**settings.DATABASE)"
print "... ", URL(**settings.DATABASE)
print "...above should read: "
print "... postgresql://ebroot:42Snails#aa12jlddfw2awrj.cc6p0ojvcx3g.us-east-1.rds.amazonaws.com:5432/ebdb"
print ".............................................."
print "...attempting engine = create_engine(URL(**settings.DATABASE))..."
try:
engine = create_engine(URL(**settings.DATABASE))
print "...Succeeded in creating engine.................."
return engine
except:
print "..................................................."
print "...Failed to create engine in database_setup.py...."
print "..................................................."
raise
def makeSession():
# Establishes a session called session which allows you to work with the DB
try:
print "....trying to create session.................."
engine = db_connect()
print "....succeeded in db_connect().................."
Base.metadata.bind = engine
print "....succeeded in Base.metadata.bind = engine..."
# create a configured "Session" class
Session = sessionmaker(bind=engine)
print "....succeeded in Session = sessionmaker(bind=engine)..."
# create a Session
session = Session()
print ".............................................."
print "...Succeeded in creating session.............."
print ".............................................."
return session
except:
print "................................................."
print "...Failed to create session in application.py...."
print "................................................."
raise
print "finally.... session.close()"
session.close()
This is a snippet from /var/log/httpd/error_log. Lines beggining with "..." are print statements I am using to isolate the issue. I have altered the url I use to get to the database to frustrate the robots. The address I use works perfectly from my local machine and from the terminal when I ssh into the app server.
[Sat Mar 19 20:16:00.159375 2016] [mpm_prefork:notice] [pid 670] AH00169: caught SIGTERM, shutting down
[Sat Mar 19 20:16:01.259575 2016] [suexec:notice] [pid 1077] AH01232: suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
[Sat Mar 19 20:16:01.270801 2016] [so:warn] [pid 1077] AH01574: module wsgi_module is already loaded, skipping
[Sat Mar 19 20:16:01.273963 2016] [auth_digest:notice] [pid 1077] AH01757: generating secret for digest authentication ...
[Sat Mar 19 20:16:01.274662 2016] [lbmethod_heartbeat:notice] [pid 1077] AH02282: No slotmem from mod_heartmonitor
[Sat Mar 19 20:16:01.274712 2016] [:warn] [pid 1077] mod_wsgi: Compiled for Python/2.7.9.
[Sat Mar 19 20:16:01.274719 2016] [:warn] [pid 1077] mod_wsgi: Runtime using Python/2.7.10.
[Sat Mar 19 20:16:01.276674 2016] [mpm_prefork:notice] [pid 1077] AH00163: Apache/2.4.16 (Amazon) mod_wsgi/3.5 Python/2.7.10 configured -- resuming normal operations
[Sat Mar 19 20:16:01.276690 2016] [core:notice] [pid 1077] AH00094: Command line: '/usr/sbin/httpd -D FOREGROUND'
[Sat Mar 19 20:16:04.069713 2016] [:error] [pid 1080] ...in settings.py.......
[Sat Mar 19 20:19:53.419659 2016] [:error] [pid 1080] ....trying to create session..................
[Sat Mar 19 20:19:53.419702 2016] [:error] [pid 1080] ..............................................
[Sat Mar 19 20:19:53.419707 2016] [:error] [pid 1080] ...Connecting to Database at URL :
[Sat Mar 19 20:19:53.419711 2016] [:error] [pid 1080] ...attempting URL(**settings.DATABASE)
[Sat Mar 19 20:19:53.419876 2016] [:error] [pid 1080] ... postgresql://user:password#aa12jlddfw2awrj.cc6p9990ojvcx3g.us-east-1.rds.amazonaws.com:5432/ebdb
[Sat Mar 19 20:19:53.419884 2016] [:error] [pid 1080] ...above should read:
[Sat Mar 19 20:19:53.419889 2016] [:error] [pid 1080] ... postgresql://user:password#aa12jlddfw2awrj.cc6p9990ojvcx3g.us-east-1.rds.amazonaws.com:5432/ebdb
[Sat Mar 19 20:19:53.419893 2016] [:error] [pid 1080] ..............................................
[Sat Mar 19 20:19:53.419897 2016] [:error] [pid 1080] ...attempting engine = create_engine(URL(**settings.DATABASE))...
[Sat Mar 19 20:19:53.427168 2016] [:error] [pid 1080] ...................................................
[Sat Mar 19 20:19:53.427189 2016] [:error] [pid 1080] ...Failed to create engine in database_setup.py....
[Sat Mar 19 20:19:53.427193 2016] [:error] [pid 1080] ...................................................
[Sat Mar 19 20:19:53.427200 2016] [:error] [pid 1080] .................................................
[Sat Mar 19 20:19:53.427203 2016] [:error] [pid 1080] ...Failed to create session in application.py....
[Sat Mar 19 20:19:53.427206 2016] [:error] [pid 1080] .................................................
Here is the url for the running app:
http://keirseysorterapp.9yk6hymk2z.us-east-1.elasticbeanstalk.com/testApp

Answer 1

I was never able to get this to work. I ended up following this tutorial:
https://medium.com/#rodkey/deploying-a-flask-application-on-aws-a72daba6bb80#.t2lbbv5q3
The tutorial uses the Flask-SQLAlchemy module instead of importing Flask and SQLAlchemy separately. Once I used this method I had no problems. Good luck!