func NewManager()

in lib/backend/manager.go [62:104]
40 lines of code
10 McCabe index (conditional complexity)

func NewManager(managerConfig ManagerConfig, configs []Config, auth AuthConfig, stats tally.Scope) (*Manager, error) {
	logger, err := log.New(managerConfig.Log, nil)
	if err != nil {
		return nil, fmt.Errorf("log: %s", err)
	}
	slogger := logger.Sugar()

	var backends []*backend
	for _, config := range configs {
		config = config.applyDefaults()
		var c Client

		if len(config.Backend) != 1 {
			return nil, fmt.Errorf("no backend or more than one backend configured")
		}
		var backendName string
		var backendConfig interface{}
		for backendName, backendConfig = range config.Backend { // Pull the only key/value out of map
		}
		factory, err := getFactory(backendName)
		if err != nil {
			return nil, fmt.Errorf("get backend client factory: %s", err)
		}
		c, err = factory.Create(backendConfig, auth, stats, slogger)
		if err != nil {
			return nil, fmt.Errorf("create backend client: %s", err)
		}

		if config.Bandwidth.Enable {
			l, err := bandwidth.NewLimiter(config.Bandwidth)
			if err != nil {
				return nil, fmt.Errorf("bandwidth: %s", err)
			}
			c = throttle(c, l)
		}
		b, err := newBackend(config.Namespace, c, config.MustReady)
		if err != nil {
			return nil, fmt.Errorf("new backend for namespace %s: %s", config.Namespace, err)
		}
		backends = append(backends, b)
	}
	return &Manager{backends}, nil
}