Test database accessibility in Django

Question

My question is very similar to this question

I'm just getting started with Django, and I find myself attempting to learn how it works any time I have a spare moment and my laptop available. I've found that Heroku is a pretty great place to test things, but I can't always reach the internet if I'm waiting to pick up kids, or something similar. In development, I would like to create a test that will check if a DB is accessible. If not, fail over to an SQLite DB.

I started with code heavily borrowed from here :

def pingable(hostname):
    try:
        return os.system("ping -c 1 " + hostname  + " > /dev/null 2>&1") == 0
    except:
        return False

if (not pingable(DATABASES['default']['HOST'])):
    DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.sqlite3',
            'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
        }
    }

I simply plop that code immediately after the DATABASES variable is set. But this has a few weaknesses. The most glaring is that AWS (Which Heroku uses) doesn't respond to pings unless you specifically enable them . . . and honestly, why make things less secure if you don't have to?

So in the interest of not reinventing the wheel, this has led me to ask this question: has someone created a way to check if a Django DB is accessible?

I really only need to check Postgres . . . but I'd really love to find a generic solution, so half credit if you can point me to a solution that only works for Postgres.

Edit: To clarify, the internet itself may be available, but the necessary port(s) may be blocked by a firewall . . . it's hard to know what will be available

Answer 1

This isn't really the way to manage database settings between Heroku and your local dev machine.

Heroku manages all these sorts of settings via environment variables, which is one of the principles of the 12-factor app . They've also made a Django library, dj-database-url , which reads those env vars and automatically configures the settings appropriately.

You should use this for your database settings, and then you can set a local env var DATABASE_URL with the address of your local sqlite3 database. Then your app will automatically run in both dev and production and configure itself to point to the relevant database automatically.