log

type LogRecord struct {
	Run      string
	Id       string
	Time     time.Time
	Messages []Message
}

type Logger interface {

	// async logging
	Add(interface{})

	// returns only when log is committed to permanent storage
	AddSync(interface{}) error

	Flush()
}

type Message struct {
	Time    time.Time
	Id      string
	Payload interface{}
}

type Message2 struct {
	Message
	Type  string
	Reply chan error
}