leader

type Candidate interface {
	IsLeader() bool
	Start() error
	Stop() error
	Resign()
}

type Discovery interface {

	// Returns the app URL for a given Peloton role such as
	// peloton-jobmgr, peloton-resmgr or peloton-hostmgr etc.
	GetAppURL(role string) (*url.URL, error)
}

type ElectionConfig struct {
	// A comma separated list of ZK servers to use for leader election.
	ZKServers []string `yaml:"zk_servers"`

	// The root path in ZK to use for role leader election.
	// This will be something like /peloton/YOURCLUSTERHERE.
	Root string `yaml:"root"`
}

type Endpoint struct {
	Host string `json:"host"`
	Port int    `json:"port"`
}

type ID struct {
	Hostname string `json:"hostname"`
	IP       string `json:"ip"`
	HTTPPort int    `json:"http"`
	GRPCPort int    `json:"grpc"`
	Version  string `json:"version"`
}

type Nomination interface {
	// GainedLeadershipCallback is the callback when the current node
	// becomes the leader
	GainedLeadershipCallback() error

	// HasGainedLeadership returns true iff once GainedLeadershipCallback
	// completes
	HasGainedLeadership() bool

	// ShutDownCallback is the callback to shut down gracefully if
	// possible
	ShutDownCallback() error

	// LostLeadershipCallback is the callback when the leader lost
	// leadership
	LostLeadershipCallback() error

	// GetID returns the host:master_port of the node running for
	// leadership (i.e. the ID)
	GetID() string
}

type Observer interface {
	CurrentLeader() (string, error)
	Start() error
	Stop()
}

type ServiceInstance struct {
	ServiceEndpoint     Endpoint            `json:"serviceEndpoint"`
	AdditionalEndpoints map[string]Endpoint `json:"additionalEndpoints"`
	Status              string              `json:"status"`
}