naming

type Builder interface {
	Build(id string) Resolver
	Scheme() string
}

type Instance struct {
	// Region is region.
	Region string `json:"region"`
	// Zone is IDC.
	Zone string `json:"zone"`
	// Env prod/pre、uat/fat1
	Env string `json:"env"`
	// AppID is mapping servicetree appid.
	AppID string `json:"appid"`
	// Hostname is hostname from docker.
	Hostname string `json:"hostname"`
	// Addrs is the address of app instance
	// format: scheme://host
	Addrs []string `json:"addrs"`
	// Version is publishing version.
	Version string `json:"version"`
	// LastTs is instance latest updated timestamp
	LastTs int64 `json:"latest_timestamp"`
	// Metadata is the information associated with Addr, which may be used
	// to make load balancing decision.
	Metadata map[string]string `json:"metadata"`
}

type InstancesInfo struct {
	Instances map[string][]*Instance `json:"instances"`
	LastTs    int64                  `json:"latest_timestamp"`
	Scheduler []Zone                 `json:"scheduler"`
}

type Registry interface {
	Register(ctx context.Context, ins *Instance) (cancel context.CancelFunc, err error)
	Close() error
}

type Resolver interface {
	Fetch(context.Context) (*InstancesInfo, bool)
	Watch() <-chan struct{}
	Close() error
}

type Zone struct {
	Src string           `json:"src"`
	Dst map[string]int64 `json:"dst"`
}