Understanding the populate_mongodb_backend() function

[oshihirii]

simple_webapp_using_mongodb.py starts with a function:

populate_mongodb_backend()

I understand that it populates the database with:

• admin user to users collection
• admin, editor and user roles to roles collection

but I ran my app containing this function once and it went through fine, I ran it again and I got:

pymongo.errors.DuplicateKeyError: E11000 duplicate key error index: cork-example
.users.$login_1  dup key: { : "admin" }

I understand the error, that there is a duplicate, but I don't understand why the function is included like that - is it intended to run every time the program is run?

Or is it intended to just be run once and then commented out?

I don't think I could do the latter as it is intertwined with the next part of the code:

mb = populate_mongodb_backend()
aaa = Cork(backend=mb, email_sender='federico.ceratto@gmail.com', smtp_url='smtp://smtp.magnet.ie')

and aaa is then used frequently thoughout the rest of the code.

[FedericoCeratto]

The example application is meant to be start and populate the database under the assumption that the database is empty.

[oshihirii]

The function that populates the database is assigned to the variable mb.

Then mb is a value assigned to the backend parameter of aaa, an instantiation of the Cork class.

aaa is then used throughout the rest of the program (aaa.login and aaa.register etc).

I cannot therefore comment out the function, because aaa seems to depend on it being there.

I cannot leave the function in though, because it seems it is causing the duplicate error?

To clarify:

• I delete cork-example database.
• I run the application once (database is created and populated).
• I run the application again, and a duplicate error occurs.

[oshihirii]

Solution (i think)

I looked at this tutorial's code and noticed that backend didn't seem to be assigned the value of a function, so I commented out the populate_mongodb_backend() function (as the database has already been populated) and modifed the code to the following and now I can login and access all admin pages etc:

hostname = os.environ['OPENSHIFT_MONGODB_DB_URL']
connection = pymongo.MongoClient(host=hostname)
mb = MongoDBBackend(db_name='cork-example', initialize=True,hostname = hostname)
aaa = Cork(backend=mb, email_sender='federico.ceratto@gmail.com', smtp_url='smtp://smtp.magnet.ie')