Flask Subdomain with Heroku and Godaddy (SERVER_NAME issues)

Question

I am trying to set up a subdomain on a flask server, which has a server hosted on Heroku and a custom domain hosted on GoDaddy. I have verified that my subdomain is working locally. The subdomain is a separate blueprint in my app. My setup in flask is:

blueprint = Blueprint('blueprint', __name__, template_folder="templates", subdomain="blueprint")

@blueprint.route('/')
def index():
    return "Hello Mate"

and then

app.config['SERVER_NAME'] = os.environ['MY_SERVER_NAME']
from blueprint.views import blueprint
    app.register_blueprint(blueprint)

On my local machine, I set up a custom record in my hosts file (/etc/hosts) to test the subdomain. The file has the entries:

127.0.0.1 virtual.local
127.0.0.1 blueprint.virtual.local

If I navigate to blueprint.virtual.local:5000, I see the intended result (a page that just says Hello Mate. I believe this proves my subdomain settings are set up properly, at least within flask.

I push my code to my heroku app, and this is where I start running into problems. My heroku site has a custom domain associated with it from before. I start by adding an entry for the new subdomain. Running heroku domains in the terminal gives me:

=== myapp Domain Names
blueprint.mysite.com
www.mysite.com
myapp.herokuapp.com
mysite.com

The first issue I am running into is that I can only either view my site on the heroku URL or the custom domain. This is a result of app.config['SERVER_NAME'] (which I set to get my subdomain working) being linked to either the heroku URL or my custom URL. When it is set to the heroku URL, I can only see the site when I visit it at that URL, and when I go to my custom domain, I get a 404 error. This is reversed when I switch the value of the SERVER_NAME.

The second issue is that I cannot get my subdomain to work with GoDaddy on Heroku. In GoDaddy, I create a CNAME record that points my subdomain (blueprint) to my heroku site (myapp.herokuapp.com). Is this correct? I get a 404 error whenever I visit the subdomain on my custom domain (blueprint.mysite.com). I believe this is related to the first issue, but I am not sure. Am I missing any steps?

Any advice on the proper way to set this up, so that I can use Flask subdomains on Heroku, being hosted on a custom domain on GoDaddy? Thanks in advance!

Darrell Silver Darrell Silver · Accepted Answer · 2015-02-18T00:47:57

I suspect you're confusing Flask Blueprints and Heroku apps. A flask app (and its containing git repository, in this case) is one and only one Heroku app (a single domain, or subdomian... but crucially, only one of them).

A Flask Blueprint is a way of organizing individual sections of a single Flask app to be more modular.

To create Heroku Apps at awesome.darrellsilver.com and sauce.darrellsilver.com you should set up two independent Flask Apps, in two independent Git repos.

Flask Subdomain with Heroku and Godaddy (SERVER_NAME issues)

2 Answers