Function loadConfig

cmd/tempo/main.go:135–217

()

}

func loadConfig() (*app.Config, bool, error) {
	const (
		configFileOption      = "config.file"
		configExpandEnvOption = "config.expand-env"
		configVerifyOption    = "config.verify"
	)

	var (
		configFile      string
		configExpandEnv bool
		configVerify    bool
	)

	args := os.Args[1:]
	config := &app.Config{}

	// first get the config file
	fs := flag.NewFlagSet("", flag.ContinueOnError)
	fs.SetOutput(io.Discard)

	fs.StringVar(&configFile, configFileOption, "", "")
	fs.BoolVar(&configExpandEnv, configExpandEnvOption, false, "")
	fs.BoolVar(&configVerify, configVerifyOption, false, "")

	// Try to find -config.file & -config.expand-env flags. As Parsing stops on the first error, eg. unknown flag,
	// we simply try remaining parameters until we find config flag, or there are no params left.
	// (ContinueOnError just means that flag.Parse doesn't call panic or os.Exit, but it returns error, which we ignore)
	for len(args) > 0 {
		_ = fs.Parse(args)
		args = args[1:]
	}

	// load config defaults and register flags
	config.RegisterFlagsAndApplyDefaults("", flag.CommandLine)

	// overlay with config file if provided
	if configFile != "" {
		buff, err := os.ReadFile(configFile)
		if err != nil {
			return nil, false, fmt.Errorf("failed to read configFile %s: %w", configFile, err)
		}

		if configExpandEnv {
			s, err := envsubst.EvalEnv(string(buff))
			if err != nil {
				return nil, false, fmt.Errorf("failed to expand env vars from configFile %s: %w", configFile, err)
			}
			buff = []byte(s)
		}

		err = yaml.UnmarshalStrict(buff, config)
		if err != nil {
			return nil, false, fmt.Errorf("failed to parse configFile %s: %w", configFile, err)
		}

	}

	// Pass --config.expand-env flag to overrides module