CODEWITHSUNDEEP
pythongoogle-app-engineyaml
user2091046
user2091046

Reputation: 625

Python and YAML- GAE app settings file

I was reading about using YAML to store settings in a GAE application and I think I want to go this way. I'm talking about my own constants like API keys and temp variables, NOT about standard GAE config files like app.yaml.

So far I used a simple settings.py file for it (which included separate configs for production/testing/etc environment), but it doesn't seem to do the job well enough.

I even had some serious problems when a git merge overwrote some settings (hard to control it).

Eventually I want to store as much data as I can in the data store but as for now I'm looking for ideas.

So does anybody have any ideas or examples for simple storing and access of, sometimes protected, config data?

Upvotes: 2

Views: 1051

Answers (2)

Martin Omander
Martin Omander

Reputation: 3594

You should not store config values in source code, for the reasons outlined in the other answers. In my latest project, I put config data in the datastore using this class:

from google.appengine.ext import ndb

class Settings(ndb.Model):
  name = ndb.StringProperty()
  value = ndb.StringProperty()

  @staticmethod
  def get(name):
    NOT_SET_VALUE = "NOT SET"
    retval = Settings.query(Settings.name == name).get()
    if not retval:
      retval = Settings()
      retval.name = name
      retval.value = NOT_SET_VALUE
      retval.put()
    if retval.value == NOT_SET_VALUE:
      raise Exception(('Setting %s not found in the database. A placeholder ' +
        'record has been created. Go to the Developers Console for your app ' +
        'in App Engine, look up the Settings record with name=%s and enter ' +
        'its value in that record\'s value field.') % (name, name))
    return retval.value

Your application would do this to get a value:

AMAZON_KEY = Settings.get('AMAZON_KEY')

If there is a value for that key in the datastore, you will get it. If there isn't, a placeholder record will be created and an exception will be thrown. The exception will remind you to go to the Developers Console and update the placeholder record.

I find this takes the guessing out of setting config values. If you are unsure of what config values to set, just run the code and it will tell you!

Upvotes: 1

Lipis
Lipis

Reputation: 21835

Storing the API keys and configuration variables in static files is usually always a bad idea for a few reasons:

  • Hard to update: you need to deploy a new app in order to update the values
  • Not secure: you might commit it to the version control system and there is no way back
  • Don't scale: very often you have different keys for different domains

So why not storing all these values right from the very beginning securely in the datastore, especially when it's actually so much easier and here is how:

All you have to do is to create one new model for your configuration values and have only one record in it. By using NDB, you have caching out of the box and because of the nature of this configuration file you can even cache it per running instance to avoid regular reads to the datastore.

class Config(ndb.Model):
  analytics_id = ndb.StringProperty(default='')
  brand_name = ndb.StringProperty(default='my-awesome-app')
  facebook_app_id = ndb.StringProperty(default='')
  facebook_app_secret = ndb.StringProperty(default='')

  @classmethod
  def get_master_db(cls):
    return cls.get_or_insert('master')

I'm also guessing that you already have one file that most likely is called config.py where you have some constants like these ones:

PRODUCTION = os.environ.get('SERVER_SOFTWARE', '').startswith('Google App Engine')
DEVELOPMENT = not PRODUCTION

If you don't create one or if you do just add this to that file as well:

import model   # Your module that contains the models

CONFIG_DB = model.Config.get_master_db()

and finally to be able to read your config values you can simply do that, wherever in your app (after importing the config.py of course):

config.CONFIG_DB.brand_name

From now on you don't even have to create any special forms to update these values (it is recommended though), because you can do that from the admin console locally or the Dashboard on the production.

Just remember that if you're going to store that record in a local variable you will have to restart the instances after updating the values to see the changes.

All of the above you can see it in action, in one of my open sourced projects called gae-init.

Upvotes: 2

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