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https://github.com/cloud66-oss/konfig

A Kubernetes friendly Rails configuration gem.
https://github.com/cloud66-oss/konfig

configuration kubernetes rails

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A Kubernetes friendly Rails configuration gem.

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# Konfig



Konfig is a Kubernetes friendly Rails configuration file. While Rails applications can easily read YAML files to load configurations, Kubernetes is good at serving individual configuration values as files via Kubernetes Secrets. This means your Rails application needs to read the same configuration file from a YAML file in development or an individual file while running in Kubernetes. Konfig can load configuration and secrets from both YAML or folders with individual files and present them to your application the same way.



## Installation



Add this line to your application's Gemfile:



```ruby

gem 'rb-konfig'

```



And then execute:



    $ bundle



Or install it yourself as:



    $ gem install rb-konfig



## Usage



```ruby

Konfig.configuration.mode = :yaml

Konfig.configuration.workdir = "settings/folder"

Konfig.load

```



or if you'd like to use it in Kubernetes:



```ruby

Konfig.configuration.mode = :directory

Konfig.configuration.workdir = "settings/folder"

Konfig.load

```



Now you can use Konfig anywhere in the code:



```ruby

puts Settings.some.configuration.value

```



In `file` mode, Konfig, looks for any of the files specified in `default_config_files`. By default and in a non-Rails environment this will be `development.yml` and `development.local.yml` files in `work_dir`. In a Rails environment, this will be `ENVIRONMENT.yml` and `ENVIRONMENT.local.yml` files (ie `production.yml` and `production.local.yml`) files. Files added to the list later will override the values in the earlier defined files. This means, `production.local.yml` values will override `production.yml` values.

In `kubernetes` mode, it looks for a file for each one of the given configuration keys. For example:



```yml

# development.yml

some:

    configuration:

        value: true

```



```bash

# directory mode

$ ls config/settings

-rw-r--r--    1 khash  staff    20 10 May 07:20 some.configuration.value



$ cat config/settings/some.configuration.value

true

```



The value in `some.configuration.value` file can be `true`. Konfig tries to clean the file and coerce the value into the right type before returning. If the file or the key in yaml is missing, it will return a `Konfig::MissingConfiguration` is thrown.



### NULL / nil values



By default YAML returns `nil` for a `null` value in a YAML file. This is also replicated in directory mode.



### Environment Variable Overrides



Settings can be overridden by values in environment variables. To override a value, set an environment variable that reflects the full path to the setting, replacing `.` with `_` and prefixing it with `KONFIG_`. You can change the prefix using `Konfig.configuration.env_prefix`. For example, `Settings.this.is.a.test` can be overridden with `KONFIG_THIS_IS_A_TEST`. Environment variables are not parsed for Ruby (ERB) but are coerced into the right type just like other settings.



### Configuration

You can change or reach the following from `Konfig.configuration`



* `namespace`: Default is `Settings`

* `delimiter`: Default is `.`

* `default_config_files`: Default is [`development.yml`, `development.local.yml`]

* `allow_nil`: Default is `true`

* `nil_word`: Default is `null`

* `mode`: No default value

* `workdir`: No default value

* `schema`: Configuration validation schema. If available, the loaded, merged and parsed configuration is validated against this schema. See [Dry-Schema](https://dry-rb.org/gems/dry-schema/) for more information.

* `fail_on_validation`: Fail if schema validation fails



### Data types



The directory mode, supports the following data types in files and tries to return the right type:



- Integer

- Float

- String

- Boolean

- JSON

- Null (see above)



### ERB



YAML mode supports ERB in your YAML file, just like default Rails behavior



## Development



After checking out the repo, run `bin/setup` to install dependencies. You can also run `bin/console` for an interactive prompt that will allow you to experiment.



To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).



## CLI



Konfig has a CLI to generate validation schema based on a given yaml file. To generate, run:



```bash

$ konfig gs --in sample.yml

```



This will generate the ruby code that can be used for `Konfig.configuration.schema` like the one below:



```ruby

Konfig.configuration.schema do

  required(:some).schema do

    required(:setting).filled(:string)

    required(:another).filled(:integer)

    required(:and_more).filled(:bool)

  end

end

```



## Contributing



Bug reports and pull requests are welcome on GitHub at https://github.com/cloud66-oss/konfig.