raft/raft.go
func (r *raft) bcastAppend() {
	r.forEachProgress(func(id uint64, _ *Progress) {
		if id == r.id {
			return
		}

		r.sendAppend(id)
	})
}
func (r *raft) bcastAppend() {
	r.forEachProgress(func(id uint64, _ *Progress) {
		if id == r.id {
			return
		}

		r.sendAppend(id)
	})
}
// bcastAppend sends RPC, with entries to all peers that are not up-to-date
// according to the progress recorded in r.prs.