IService

The config.IService interface describes a service that manages configurations, usually of types.

The add method is used to register a config.spec.IRuleSet to the service.

The getAsync method gets a filtered configuration for a given environment.

From the returned configuration, rules for specific types or instances can be obtained by calling its selectType and selectInstance, respectively.

Rules that apply to a given type/instance and environment variables are sorted by specificity and then their specifications are merged. For more information on the specificity of rules, see config.spec.IRuleSet.

Suppose that the following rule set is defined in the system:

{
  "rules": [
    // Disable a still experimental component.
    {
      "select": {
        "type": "my.foo.component"
      },
      "apply": {
        "enabled": false
      }
    },

    // Enable it, only for the dev user, "john", and the "super-app" application.
    {
      "select": {
        "type":        "my.foo.component",
        "user":        "john",
        "application": "super-app"
      },
      "apply": {
        "enabled": true
      }
    }
  ]
}

Now, given some implementation of a configuration service, we could use it like in the following example:

configService.getAsync({
  user:        "john",
  application: "not-so-super-app"
}).then(function(config) {

  var mergedConfigSpec = config.selectType("my.foo.component");

  // Results in a configuration specification like:
  // {
  //   enabled: false
  // }
});