func (s Status) MarshalJSON() ([]byte, error) {
	j := fmt.Sprintf(`{"id":"%x","term":%d,"vote":"%x","commit":%d,"lead":"%x","raftState":%q,"progress":{`,
		s.ID, s.Term, s.Vote, s.Commit, s.Lead, s.RaftState)
	if len(s.Progress) == 0 {
		j += "}}"
	} else {
		for k, v := range s.Progress {
			subj := fmt.Sprintf(`"%x":{"match":%d,"next":%d,"state":%q},`, k, v.Match, v.Next, v.State)
			j += subj
		}
		j = j[:len(j)-1] + "}}"
	}
	return []byte(j), nil
}
TODO: try to simplify this by introducing ID type into raft
package raft
import (
	"fmt"
	pb "github.com/coreos/etcd/raft/raftpb"
)
type Status struct {
	ID uint64
	pb.HardState
	SoftState
	Applied  uint64
	Progress map[uint64]Progress
}
func getStatus(r *raft) Status {
	s := Status{ID: r.id}
	s.HardState = r.HardState
	s.SoftState = *r.softState()
	s.Applied = r.raftLog.applied
	if s.RaftState == StateLeader {
		s.Progress = make(map[uint64]Progress)
		for id, p := range r.prs {
			s.Progress[id] = *p
		}
	}
	return s
}