settings.py

"""
This module encapsulates all knowledge about what environment your
code is running in (ie: development / production). 

Note: make sure all calls to settings.get() are done at runtime, and not at import time.

usage:

    import settings
    def test():
        remote_endpoint = settings.get("remote_endpoint")
        ...

"""
import tornado.options
import random
tornado.options.define("environment", default="dev", help="environment")


def randomize(values):
    """ this is a wrapper that returns a function which when called returns a random value"""
    def picker():
        return random.choice(values)
    return picker

# settings that are different for each environment 
# (ie: pointers to remote endpoints)
options = {
    "dev" : {
        "remote_endpoint" : "http://127.0.0.1:8080",
    },
    
    "prod" : {
        "remote_endpoint" : randomize(["http://remote-server1.com",
                                        "http://remote-server2.com"]),
    }
}

# settings that are the same for each environment
# (ie: they are here just to make them easy to find/change/update)
default_options = {
    "num_records_to_return" : 15,
}

def get(key):
    env = tornado.options.options.environment
    if env not in options:
        raise Exception("Invalid Environment (%s)" % env)
    v = options.get(env).get(key) or default_options.get(key)
    if callable(v):
        return v()
    return v