Skeleton settings.py used by data-infra squad

settings.py

import json
import os
import socket

import tornado.options


tornado.options.define('environment', default='dev', help='environment')

app_name = os.path.basename(os.path.dirname(__file__))

environment_settings = {
    'dev': {
    },
    'stage': {
    },
    'live': {
    }
}
# FIXME: this hacks in support for chef's environments; we should unify these
environment_settings['development'] = environment_settings['dev']
environment_settings['production'] = environment_settings['live']

host_settings = {
}

default_settings = {
}


def env():
    return tornado.options.options.environment


def memoized(f, cache={}):
    def decorated():
        if f.__name__ not in cache:
            cache[f.__name__] = f()
        return cache[f.__name__]
    return decorated


@memoized
def hostname():
    fqdn = socket.gethostname()
    return 'dev.buzzfeed.org' if fqdn.endswith('.buzzfeed.org') else fqdn


@memoized
def local_settings():
    try:
        with open('/buzzfeed/local/conf/%s/settings.json' % app_name) as f:
            settings = json.load(f)
            assert isinstance(settings, dict)
            return settings
    except IOError:
        return {}
    except Exception, e:
        raise RuntimeError('Invalid local settings.json: %s' % e)


def get(key):
    env = tornado.options.options.environment
    if env not in environment_settings:
        raise Exception('Invalid Environment (%s)' % env)

    v = os.environ.get(key.upper())

    if v is None:
        v = local_settings().get(key)

    if v is None:
        v = host_settings.get(hostname(), {}).get(key)

    if v is None:
        v = environment_settings.get(env).get(key)

    if v is None:
        v = default_settings.get(key)

    assert v is not None, 'key %s not in any settings' % key

    if callable(v):
        return v()

    return v