// writeError logs and writes the given Error to the ResponseWriter
// If Error is an etcdErr, it is rendered to the ResponseWriter
// Otherwise, it is assumed to be a StatusInternalServerError
func writeError(w http.ResponseWriter, r *http.Request, err error) {
	if err == nil {
		return
	}
	switch e := err.(type) {
	case *etcdErr.Error:
		e.WriteTo(w)
	case *httptypes.HTTPError:
		if et := e.WriteTo(w); et != nil {
			plog.Debugf("error writing HTTPError (%v) to %s", et, r.RemoteAddr)
		}
	case auth.Error:
		herr := httptypes.NewHTTPError(e.HTTPStatus(), e.Error())
		if et := herr.WriteTo(w); et != nil {
			plog.Debugf("error writing HTTPError (%v) to %s", et, r.RemoteAddr)
		}
	default:
		switch err {
		case etcdserver.ErrTimeoutDueToLeaderFail, etcdserver.ErrTimeoutDueToConnectionLost, etcdserver.ErrNotEnoughStartedMembers:
			mlog.MergeError(err)
		default:
			mlog.MergeErrorf("got unexpected response error (%v)", err)
		}
		herr := httptypes.NewHTTPError(http.StatusInternalServerError, "Internal Server Error")
		if et := herr.WriteTo(w); et != nil {
			plog.Debugf("error writing HTTPError (%v) to %s", et, r.RemoteAddr)
		}
	}
}

func unmarshalRequest(r *http.Request, req json.Unmarshaler, w http.ResponseWriter) bool {
	ctype := r.Header.Get("Content-Type")
	if ctype != "application/json" {
		writeError(w, r, httptypes.NewHTTPError(http.StatusUnsupportedMediaType, fmt.Sprintf("Bad Content-Type %s, accept application/json", ctype)))
		return false
	}
	b, err := ioutil.ReadAll(r.Body)
	if err != nil {
		writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, err.Error()))
		return false
	}
	if err := req.UnmarshalJSON(b); err != nil {
		writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, err.Error()))
		return false
	}
	return true
}

func (s *EtcdServer) Process(ctx context.Context, m raftpb.Message) error {
	if s.cluster.IsIDRemoved(types.ID(m.From)) {
		plog.Warningf("reject message from removed member %s", types.ID(m.From).String())
		return httptypes.NewHTTPError(http.StatusForbidden, "cannot process message from removed member")
	}
	if m.Type == raftpb.MsgApp {
		s.stats.RecvAppendReq(types.ID(m.From).String(), m.Size())
	}
	return s.r.Step(ctx, m)
}

func unmarshalRequest(r *http.Request, req json.Unmarshaler, w http.ResponseWriter) bool {
	ctype := r.Header.Get("Content-Type")
	semicolonPosition := strings.Index(ctype, ";")
	if semicolonPosition != -1 {
		ctype = strings.TrimSpace(strings.ToLower(ctype[0:semicolonPosition]))
	}
	if ctype != "application/json" {
		writeError(w, r, httptypes.NewHTTPError(http.StatusUnsupportedMediaType, fmt.Sprintf("Bad Content-Type %s, accept application/json", ctype)))
		return false
	}
	b, err := ioutil.ReadAll(r.Body)
	if err != nil {
		writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, err.Error()))
		return false
	}
	if err := req.UnmarshalJSON(b); err != nil {
		writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, err.Error()))
		return false
	}
	return true
}

func (h *statsHandler) serveLeader(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "GET") {
		return
	}
	stats := h.stats.LeaderStats()
	if stats == nil {
		writeError(w, r, httptypes.NewHTTPError(http.StatusForbidden, "not current leader"))
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Write(stats)
}

func getID(p string, w http.ResponseWriter) (types.ID, bool) {
	idStr := trimPrefix(p, membersPrefix)
	if idStr == "" {
		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
		return 0, false
	}
	id, err := types.IDFromString(idStr)
	if err != nil {
		writeError(w, nil, httptypes.NewHTTPError(http.StatusNotFound, fmt.Sprintf("No such member: %s", idStr)))
		return 0, false
	}
	return id, true
}

func logHandleFunc(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "PUT") {
		return
	}

	in := struct{ Level string }{}

	d := json.NewDecoder(r.Body)
	if err := d.Decode(&in); err != nil {
		writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "Invalid json body"))
		return
	}

	logl, err := capnslog.ParseLevel(strings.ToUpper(in.Level))
	if err != nil {
		writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "Invalid log level "+in.Level))
		return
	}

	plog.Noticef("globalLogLevel set to %q", logl.String())
	capnslog.SetGlobalLogLevel(logl)
	w.WriteHeader(http.StatusNoContent)
}

func (sh *authHandler) handleUsers(w http.ResponseWriter, r *http.Request) {
	subpath := path.Clean(r.URL.Path[len(authPrefix):])
	// Split "/users/username".
	// First item is an empty string, second is "users"
	pieces := strings.Split(subpath, "/")
	if len(pieces) == 2 {
		sh.baseUsers(w, r)
		return
	}
	if len(pieces) != 3 {
		writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "Invalid path"))
		return
	}
	sh.forUser(w, r, pieces[2])
}

func notCapable(w http.ResponseWriter, r *http.Request, c capability) {
	herr := httptypes.NewHTTPError(http.StatusInternalServerError, fmt.Sprintf("Not capable of accessing %s feature during rolling upgrades.", c))
	if err := herr.WriteTo(w); err != nil {
		plog.Debugf("error writing HTTPError (%v) to %s", err, r.RemoteAddr)
	}
}

func (p *reverseProxy) ServeHTTP(rw http.ResponseWriter, clientreq *http.Request) {
	proxyreq := new(http.Request)
	*proxyreq = *clientreq
	startTime := time.Now()

	var (
		proxybody []byte
		err       error
	)

	if clientreq.Body != nil {
		proxybody, err = ioutil.ReadAll(clientreq.Body)
		if err != nil {
			msg := fmt.Sprintf("proxy: failed to read request body: %v", err)
			e := httptypes.NewHTTPError(http.StatusInternalServerError, msg)
			if we := e.WriteTo(rw); we != nil {
				plog.Debugf("error writing HTTPError (%v) to %s", we, clientreq.RemoteAddr)
			}
			return
		}
	}

	// deep-copy the headers, as these will be modified below
	proxyreq.Header = make(http.Header)
	copyHeader(proxyreq.Header, clientreq.Header)

	normalizeRequest(proxyreq)
	removeSingleHopHeaders(&proxyreq.Header)
	maybeSetForwardedFor(proxyreq)

	endpoints := p.director.endpoints()
	if len(endpoints) == 0 {
		msg := "proxy: zero endpoints currently available"
		reportRequestDropped(clientreq, zeroEndpoints)

		// TODO: limit the rate of the error logging.
		log.Printf(msg)
		e := httptypes.NewHTTPError(http.StatusServiceUnavailable, msg)
		if we := e.WriteTo(rw); we != nil {
			plog.Debugf("error writing HTTPError (%v) to %s", we, clientreq.RemoteAddr)
		}
		return
	}

	var requestClosed int32
	completeCh := make(chan bool, 1)
	closeNotifier, ok := rw.(http.CloseNotifier)
	cancel := httputil.RequestCanceler(p.transport, proxyreq)
	if ok {
		go func() {
			select {
			case <-closeNotifier.CloseNotify():
				atomic.StoreInt32(&requestClosed, 1)
				log.Printf("proxy: client %v closed request prematurely", clientreq.RemoteAddr)
				cancel()
			case <-completeCh:
			}
		}()

		defer func() {
			completeCh <- true
		}()
	}

	var res *http.Response

	for _, ep := range endpoints {
		if proxybody != nil {
			proxyreq.Body = ioutil.NopCloser(bytes.NewBuffer(proxybody))
		}
		redirectRequest(proxyreq, ep.URL)

		res, err = p.transport.RoundTrip(proxyreq)
		if atomic.LoadInt32(&requestClosed) == 1 {
			return
		}
		if err != nil {
			reportRequestDropped(clientreq, failedSendingRequest)
			log.Printf("proxy: failed to direct request to %s: %v", ep.URL.String(), err)
			ep.Failed()
			continue
		}

		break
	}

	if res == nil {
		// TODO: limit the rate of the error logging.
		msg := fmt.Sprintf("proxy: unable to get response from %d endpoint(s)", len(endpoints))
		reportRequestDropped(clientreq, failedGettingResponse)
		log.Printf(msg)
		e := httptypes.NewHTTPError(http.StatusBadGateway, msg)
		if we := e.WriteTo(rw); we != nil {
			plog.Debugf("error writing HTTPError (%v) to %s", we, clientreq.RemoteAddr)
		}
		return
	}

	defer res.Body.Close()
	reportRequestHandled(clientreq, res, startTime)
//.........这里部分代码省略.........

func (sh *authHandler) forUser(w http.ResponseWriter, r *http.Request, user string) {
	if !allowMethod(w, r.Method, "GET", "PUT", "DELETE") {
		return
	}
	if !hasRootAccess(sh.sec, r, sh.clientCertAuthEnabled) {
		writeNoAuth(w, r)
		return
	}
	w.Header().Set("X-Etcd-Cluster-ID", sh.cluster.ID().String())
	w.Header().Set("Content-Type", "application/json")

	switch r.Method {
	case "GET":
		u, err := sh.sec.GetUser(user)
		if err != nil {
			writeError(w, r, err)
			return
		}

		err = r.ParseForm()
		if err != nil {
			writeError(w, r, err)
			return
		}

		uwr := userWithRoles{User: u.User}
		for _, roleName := range u.Roles {
			var role auth.Role
			role, err = sh.sec.GetRole(roleName)
			if err != nil {
				writeError(w, r, err)
				return
			}
			uwr.Roles = append(uwr.Roles, role)
		}
		err = json.NewEncoder(w).Encode(uwr)

		if err != nil {
			plog.Warningf("forUser error encoding on %s", r.URL)
			return
		}
		return
	case "PUT":
		var u auth.User
		err := json.NewDecoder(r.Body).Decode(&u)
		if err != nil {
			writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "Invalid JSON in request body."))
			return
		}
		if u.User != user {
			writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "User JSON name does not match the name in the URL"))
			return
		}

		var (
			out     auth.User
			created bool
		)

		if len(u.Grant) == 0 && len(u.Revoke) == 0 {
			// create or update
			if len(u.Roles) != 0 {
				out, err = sh.sec.CreateUser(u)
			} else {
				// if user passes in both password and roles, we are unsure about his/her
				// intention.
				out, created, err = sh.sec.CreateOrUpdateUser(u)
			}

			if err != nil {
				writeError(w, r, err)
				return
			}
		} else {
			// update case
			if len(u.Roles) != 0 {
				writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "User JSON contains both roles and grant/revoke"))
				return
			}
			out, err = sh.sec.UpdateUser(u)
			if err != nil {
				writeError(w, r, err)
				return
			}
		}

		if created {
			w.WriteHeader(http.StatusCreated)
		} else {
			w.WriteHeader(http.StatusOK)
		}

		out.Password = ""

		err = json.NewEncoder(w).Encode(out)
		if err != nil {
			plog.Warningf("forUser error encoding on %s", r.URL)
			return
		}
		return
//.........这里部分代码省略.........

func (sh *authHandler) forRole(w http.ResponseWriter, r *http.Request, role string) {
	if !allowMethod(w, r.Method, "GET", "PUT", "DELETE") {
		return
	}
	if !hasRootAccess(sh.sec, r, sh.clientCertAuthEnabled) {
		writeNoAuth(w, r)
		return
	}
	w.Header().Set("X-Etcd-Cluster-ID", sh.cluster.ID().String())
	w.Header().Set("Content-Type", "application/json")

	switch r.Method {
	case "GET":
		data, err := sh.sec.GetRole(role)
		if err != nil {
			writeError(w, r, err)
			return
		}
		err = json.NewEncoder(w).Encode(data)
		if err != nil {
			plog.Warningf("forRole error encoding on %s", r.URL)
			return
		}
		return
	case "PUT":
		var in auth.Role
		err := json.NewDecoder(r.Body).Decode(&in)
		if err != nil {
			writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "Invalid JSON in request body."))
			return
		}
		if in.Role != role {
			writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "Role JSON name does not match the name in the URL"))
			return
		}

		var out auth.Role

		// create
		if in.Grant.IsEmpty() && in.Revoke.IsEmpty() {
			err = sh.sec.CreateRole(in)
			if err != nil {
				writeError(w, r, err)
				return
			}
			w.WriteHeader(http.StatusCreated)
			out = in
		} else {
			if !in.Permissions.IsEmpty() {
				writeError(w, r, httptypes.NewHTTPError(http.StatusBadRequest, "Role JSON contains both permissions and grant/revoke"))
				return
			}
			out, err = sh.sec.UpdateRole(in)
			if err != nil {
				writeError(w, r, err)
				return
			}
			w.WriteHeader(http.StatusOK)
		}

		err = json.NewEncoder(w).Encode(out)
		if err != nil {
			plog.Warningf("forRole error encoding on %s", r.URL)
			return
		}
		return
	case "DELETE":
		err := sh.sec.DeleteRole(role)
		if err != nil {
			writeError(w, r, err)
			return
		}
	}
}

func writeNoAuth(w http.ResponseWriter, r *http.Request) {
	herr := httptypes.NewHTTPError(http.StatusUnauthorized, "Insufficient credentials")
	if err := herr.WriteTo(w); err != nil {
		plog.Debugf("error writing HTTPError (%v) to %s", err, r.RemoteAddr)
	}
}

func (h *membersHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if !allowMethod(w, r.Method, "GET", "POST", "DELETE", "PUT") {
		return
	}
	if !hasWriteRootAccess(h.sec, r, h.clientCertAuthEnabled) {
		writeNoAuth(w, r)
		return
	}
	w.Header().Set("X-Etcd-Cluster-ID", h.cluster.ID().String())

	ctx, cancel := context.WithTimeout(context.Background(), h.timeout)
	defer cancel()

	switch r.Method {
	case "GET":
		switch trimPrefix(r.URL.Path, membersPrefix) {
		case "":
			mc := newMemberCollection(h.cluster.Members())
			w.Header().Set("Content-Type", "application/json")
			if err := json.NewEncoder(w).Encode(mc); err != nil {
				plog.Warningf("failed to encode members response (%v)", err)
			}
		case "leader":
			id := h.server.Leader()
			if id == 0 {
				writeError(w, r, httptypes.NewHTTPError(http.StatusServiceUnavailable, "During election"))
				return
			}
			m := newMember(h.cluster.Member(id))
			w.Header().Set("Content-Type", "application/json")
			if err := json.NewEncoder(w).Encode(m); err != nil {
				plog.Warningf("failed to encode members response (%v)", err)
			}
		default:
			writeError(w, r, httptypes.NewHTTPError(http.StatusNotFound, "Not found"))
		}
	case "POST":
		req := httptypes.MemberCreateRequest{}
		if ok := unmarshalRequest(r, &req, w); !ok {
			return
		}
		now := h.clock.Now()
		m := membership.NewMember("", req.PeerURLs, "", &now)
		err := h.server.AddMember(ctx, *m)
		switch {
		case err == membership.ErrIDExists || err == membership.ErrPeerURLexists:
			writeError(w, r, httptypes.NewHTTPError(http.StatusConflict, err.Error()))
			return
		case err != nil:
			plog.Errorf("error adding member %s (%v)", m.ID, err)
			writeError(w, r, err)
			return
		}
		res := newMember(m)
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusCreated)
		if err := json.NewEncoder(w).Encode(res); err != nil {
			plog.Warningf("failed to encode members response (%v)", err)
		}
	case "DELETE":
		id, ok := getID(r.URL.Path, w)
		if !ok {
			return
		}
		err := h.server.RemoveMember(ctx, uint64(id))
		switch {
		case err == membership.ErrIDRemoved:
			writeError(w, r, httptypes.NewHTTPError(http.StatusGone, fmt.Sprintf("Member permanently removed: %s", id)))
		case err == membership.ErrIDNotFound:
			writeError(w, r, httptypes.NewHTTPError(http.StatusNotFound, fmt.Sprintf("No such member: %s", id)))
		case err != nil:
			plog.Errorf("error removing member %s (%v)", id, err)
			writeError(w, r, err)
		default:
			w.WriteHeader(http.StatusNoContent)
		}
	case "PUT":
		id, ok := getID(r.URL.Path, w)
		if !ok {
			return
		}
		req := httptypes.MemberUpdateRequest{}
		if ok := unmarshalRequest(r, &req, w); !ok {
			return
		}
		m := membership.Member{
			ID:             id,
			RaftAttributes: membership.RaftAttributes{PeerURLs: req.PeerURLs.StringSlice()},
		}
		err := h.server.UpdateMember(ctx, m)
		switch {
		case err == membership.ErrPeerURLexists:
			writeError(w, r, httptypes.NewHTTPError(http.StatusConflict, err.Error()))
		case err == membership.ErrIDNotFound:
			writeError(w, r, httptypes.NewHTTPError(http.StatusNotFound, fmt.Sprintf("No such member: %s", id)))
		case err != nil:
			plog.Errorf("error updating member %s (%v)", m.ID, err)
			writeError(w, r, err)
		default:
			w.WriteHeader(http.StatusNoContent)
//.........这里部分代码省略.........