get read-only common configs for custom application

[kamauz]

Situation:

• common configurations placed in a local yaml file

Goal:

• need to access the common configuration from the main function, in order to combine it with custom configs
  (es. cdc with database credentials passed from a common configuration)

Given the following snippet of code, I need to populate config.ServiceConfig.Database with service.config.Database , however service properties are not accessible

func main() {
	service, ok := pkg.NewAppServiceWithTargetType(serviceKey, &[]byte{})
	if !ok {
		service.LoggingClient().Errorf("App Service initialization failed for %s", serviceKey)
		os.Exit(-1)
	}

	lc := service.LoggingClient()

	config := config.ServiceConfig{}
        

        ////////////////////////////
        // <--- 
        // service.config.Database = service.config.Database   (config is a private property, not accessible)
        ////////////////////////////


	if err := service.LoadCustomConfig(&config, "CDC"); err != nil {
		lc.Errorf("LoadCustomConfig returned error: %s", err.Error())
		os.Exit(-1)
	}

	service.RegisterCustomTriggerFactory("cdc", func(config interfaces.TriggerConfig) (interfaces.Trigger, error) {
		return trigger.NewCDCTrigger(config), nil
	})
}

So I moved the focus on "LoadCustomConfig" function, but it would expect to read common configurations from a Consul.
Otherwise the private configuration is loaded as-is from the default path (res/configuration.yaml)
here's the code I'm referring to:

bootstrap/config/config.go

func (cp *Processor) LoadCustomConfigSection(updatableConfig interfaces.UpdatableConfig, sectionName string) error {
	if cp.envVars == nil {
		cp.envVars = environment.NewVariables(cp.lc)
	}

	configClient := container.ConfigClientFrom(cp.dic.Get)

        // no Configuration provider specified
	if configClient == nil {

/////////////// START /////////////////////

		cp.lc.Info("Skipping use of Configuration Provider for custom configuration: Provider not available")
		filePath := GetConfigFileLocation(cp.lc, cp.flags)
		configMap, err := cp.loadConfigYamlFromFile(filePath)
		if err != nil {
			return err
		}

		err = utils.ConvertFromMap(configMap, updatableConfig)
		if err != nil {
			return fmt.Errorf("failed to convert custom configuration into service's configuration: %v", err)
		}

/////////////// END /////////////////////

	} else {
		cp.lc.Infof("Checking if custom configuration ('%s') exists in Configuration Provider", sectionName)

		exists, err := configClient.HasSubConfiguration(sectionName)
............

[cloudxxx8]

If you don't want to use Consul to manage your config, you can disable the config provider via the environment variable
https://docs.edgexfoundry.org/3.1/microservices/configuration/CommonEnvironmentVariables/#edgex_config_provider
EDGEX_CONFIG_PROVIDER: "none"

Then, you can manage your CustomConfig in your file system.
However, the config should be read-only at runtime, and the credentials should not be passed from common config.
If you don't persist your credentials in the secret store, you can use SecretProvider() bootstrapInterfaces.SecretProvider to retrieve the credentials from the insecure section.

app-functions-sdk-go/pkg/interfaces/service.go

Line 149 in d5728ff

SecretProvider() bootstrapInterfaces.SecretProvider

Config example:
https://github.com/edgexfoundry/app-service-configurable/blob/99abc15c93f70f8386f8be99e96e68a0293bb7bf/res/mqtt-export/configuration.yaml#L70
https://docs.edgexfoundry.org/3.1/design/adr/014-Secret-Provider-For-All/