As your application matures, you may find that API credentials and configuration details change as much or more than your application code. If you tie these details too closely to your source code then you’ll be forced to redeploy for even simple configuration changes.
You may also want to share access to your source code among many developers without disclosing private credential details. For the reasons you should abstract credentials and configuration details.
Centralizing Configuration and Credential Information
Using a high-level
Config abstraction will let you encapsulate where and how this information is stored.
ENV variables are a great option for storing configuration data because they are secure yet easy to access.
This is Heroku’s preferred method for storing configuration data.
You can set ENV variables on your local machine by running a command like this:
That command is typically run in your
.bash_profile so the value persists between reboots. You can
also set different values for ENV variables on a per-command basis, like so:
You can access ENV values directly from ruby using the ENV global object, which is a Hash of all ENV values.
But doing this is not future-proof: as your app becomes more complex you may want to switch to a more fine-grained solution. Relying on ENV as your configuration abstraction does not afford enough flexibility.
Here’s an approach that will keep things simple but will allow you future flexibility. Create a file named
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This Config module encapsulates configuration details stored in ENV variables. Later you can add other sources of data like this:
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Now when you run
Config[:banned_domains] you’ll get the array defined in
Your Config object could query a secure URL for a chunk of JSON containing all of the necessary configuration/credential information needed for a new deployment.
In this case, you might only use ENV variables to store authentication details for that URL. Here’s what your
Config module might look like:
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CONFIG_URL looks like
To display current Heroku config variables, run:
All Heroku apps start out with a few basic settings like these.
Changing Heroku Settings
To add or change a setting, use this command line instruction:
If you create a separate Heroku staging app you may want to create a separate staging environment to prevent your staging app from affecting production data. The change would look like this:
Currently anyone who can push to your Heroku app can fetch and set ENV values. If you would like to share deployment responsibilities but still protect sensitive credentials you would need to implement your own security controls (perhaps through the Config object).
- ENV Variables on Heroku Dev Center: http://devcenter.heroku.com/articles/config-vars