[3.5] Backport healthcheck code cleanup

server/embed/etcd.go

@@ -747,7 +747,8 @@ func (e *Etcd) serveClients() (err error) {
 	} else {
 		mux := http.NewServeMux()
 		etcdhttp.HandleBasic(e.cfg.logger, mux, e.Server)
-		etcdhttp.HandleMetricsHealthForV3(e.cfg.logger, mux, e.Server)
+		etcdhttp.HandleMetrics(mux)
+		etcdhttp.HandleHealth(e.cfg.logger, mux, e.Server)
 		h = mux
 	}
 
@@ -836,7 +837,8 @@ func (e *Etcd) serveMetrics() (err error) {
 
 	if len(e.cfg.ListenMetricsUrls) > 0 {
 		metricsMux := http.NewServeMux()
-		etcdhttp.HandleMetricsHealthForV3(e.cfg.logger, metricsMux, e.Server)
+		etcdhttp.HandleMetrics(metricsMux)
+		etcdhttp.HandleHealth(e.cfg.logger, metricsMux, e.Server)
 
 		for _, murl := range e.cfg.ListenMetricsUrls {
 			tlsInfo := &e.cfg.ClientTLSInfo

server/etcdmain/etcd.go

@@ -416,7 +416,7 @@ func startProxy(cfg *config) error {
 		go func() {
 			lg.Info("v2 proxy started listening on client requests", zap.String("host", host))
 			mux := http.NewServeMux()
-			etcdhttp.HandlePrometheus(mux) // v2 proxy just uses the same port
+			etcdhttp.HandleMetrics(mux) // v2 proxy just uses the same port
 			mux.Handle("/", ph)
 			lg.Fatal("done serving", zap.Error(http.Serve(l, mux)))
 		}()

server/etcdserver/api/etcdhttp/health.go

@@ -0,0 +1,229 @@
+// Copyright 2017 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package etcdhttp
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"go.uber.org/zap"
+
+	"github.com/prometheus/client_golang/prometheus"
+	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
+	"go.etcd.io/etcd/client/pkg/v3/types"
+	"go.etcd.io/etcd/raft/v3"
+	"go.etcd.io/etcd/server/v3/auth"
+	"go.etcd.io/etcd/server/v3/config"
+	"go.etcd.io/etcd/server/v3/etcdserver"
+)
+
+const (
+	PathHealth      = "/health"
+	PathProxyHealth = "/proxy/health"
+)
+
+type ServerHealth interface {
+	serverHealthV2V3
+	Range(context.Context, *pb.RangeRequest) (*pb.RangeResponse, error)
+	Config() config.ServerConfig
+}
+
+type serverHealthV2V3 interface {
+	Alarms() []*pb.AlarmMember
+	Leader() types.ID
+}
+
+// HandleHealth registers metrics and health handlers for v2.
+func HandleHealthForV2(lg *zap.Logger, mux *http.ServeMux, srv etcdserver.ServerV2) {
+	mux.Handle(PathHealth, NewHealthHandler(lg, func(excludedAlarms AlarmSet, serializable bool) Health {
+		if h := checkAlarms(lg, srv, excludedAlarms); h.Health != "true" {
+			return h
+		}
+		if h := checkLeader(lg, srv, serializable); h.Health != "true" {
+			return h
+		}
+		return checkV2API(lg, srv)
+	}))
+}
+
+// HandleHealth registers metrics and health handlers. it checks health by using v3 range request
+// and its corresponding timeout.
+func HandleHealth(lg *zap.Logger, mux *http.ServeMux, srv ServerHealth) {
+	mux.Handle(PathHealth, NewHealthHandler(lg, func(excludedAlarms AlarmSet, serializable bool) Health {
+		if h := checkAlarms(lg, srv, excludedAlarms); h.Health != "true" {
+			return h
+		}
+		if h := checkLeader(lg, srv, serializable); h.Health != "true" {
+			return h
+		}
+		return checkAPI(lg, srv, serializable)
+	}))
+}
+
+// NewHealthHandler handles '/health' requests.
+func NewHealthHandler(lg *zap.Logger, hfunc func(excludedAlarms AlarmSet, Serializable bool) Health) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			w.Header().Set("Allow", http.MethodGet)
+			http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
+			lg.Warn("/health error", zap.Int("status-code", http.StatusMethodNotAllowed))
+			return
+		}
+		excludedAlarms := getExcludedAlarms(r)
+		// Passing the query parameter "serializable=true" ensures that the
+		// health of the local etcd is checked vs the health of the cluster.
+		// This is useful for probes attempting to validate the liveness of
+		// the etcd process vs readiness of the cluster to serve requests.
+		serializableFlag := getSerializableFlag(r)
+		h := hfunc(excludedAlarms, serializableFlag)
+		defer func() {
+			if h.Health == "true" {
+				healthSuccess.Inc()
+			} else {
+				healthFailed.Inc()
+			}
+		}()
+		d, _ := json.Marshal(h)
+		if h.Health != "true" {
+			http.Error(w, string(d), http.StatusServiceUnavailable)
+			lg.Warn("/health error", zap.String("output", string(d)), zap.Int("status-code", http.StatusServiceUnavailable))
+			return
+		}
+		w.WriteHeader(http.StatusOK)
+		w.Write(d)
+		lg.Debug("/health OK", zap.Int("status-code", http.StatusOK))
+	}
+}
+
+var (
+	healthSuccess = prometheus.NewCounter(prometheus.CounterOpts{
+		Namespace: "etcd",
+		Subsystem: "server",
+		Name:      "health_success",
+		Help:      "The total number of successful health checks",
+	})
+	healthFailed = prometheus.NewCounter(prometheus.CounterOpts{
+		Namespace: "etcd",
+		Subsystem: "server",
+		Name:      "health_failures",
+		Help:      "The total number of failed health checks",
+	})
+)
+
+func init() {
+	prometheus.MustRegister(healthSuccess)
+	prometheus.MustRegister(healthFailed)
+}
+
+// Health defines etcd server health status.
+// TODO: remove manual parsing in etcdctl cluster-health
+type Health struct {
+	Health string `json:"health"`
+	Reason string `json:"reason"`
+}
+
+type AlarmSet map[string]struct{}
+
+func getExcludedAlarms(r *http.Request) (alarms AlarmSet) {
+	alarms = make(map[string]struct{}, 2)
+	alms, found := r.URL.Query()["exclude"]
+	if found {
+		for _, alm := range alms {
+			if len(alm) == 0 {
+				continue
+			}
+			alarms[alm] = struct{}{}
+		}
+	}
+	return alarms
+}
+
+func getSerializableFlag(r *http.Request) bool {
+	return r.URL.Query().Get("serializable") == "true"
+}
+
+// TODO: etcdserver.ErrNoLeader in health API
+
+func checkAlarms(lg *zap.Logger, srv serverHealthV2V3, excludedAlarms AlarmSet) Health {
+	h := Health{Health: "true"}
+	as := srv.Alarms()
+	if len(as) > 0 {
+		for _, v := range as {
+			alarmName := v.Alarm.String()
+			if _, found := excludedAlarms[alarmName]; found {
+				lg.Debug("/health excluded alarm", zap.String("alarm", v.String()))
+				continue
+			}
+
+			h.Health = "false"
+			switch v.Alarm {
+			case pb.AlarmType_NOSPACE:
+				h.Reason = "ALARM NOSPACE"
+			case pb.AlarmType_CORRUPT:
+				h.Reason = "ALARM CORRUPT"
+			default:
+				h.Reason = "ALARM UNKNOWN"
+			}
+			lg.Warn("serving /health false due to an alarm", zap.String("alarm", v.String()))
+			return h
+		}
+	}
+
+	return h
+}
+
+func checkLeader(lg *zap.Logger, srv serverHealthV2V3, serializable bool) Health {
+	h := Health{Health: "true"}
+	if !serializable && (uint64(srv.Leader()) == raft.None) {
+		h.Health = "false"
+		h.Reason = "RAFT NO LEADER"
+		lg.Warn("serving /health false; no leader")
+	}
+	return h
+}
+
+func checkV2API(lg *zap.Logger, srv etcdserver.ServerV2) Health {
+	h := Health{Health: "true"}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	_, err := srv.Do(ctx, pb.Request{Method: "QGET"})
+	cancel()
+	if err != nil {
+		h.Health = "false"
+		h.Reason = fmt.Sprintf("QGET ERROR:%s", err)
+		lg.Warn("serving /health false; QGET fails", zap.Error(err))
+		return h
+	}
+	lg.Debug("serving /health true")
+	return h
+}
+
+func checkAPI(lg *zap.Logger, srv ServerHealth, serializable bool) Health {
+	h := Health{Health: "true"}
+	cfg := srv.Config()
+	ctx, cancel := context.WithTimeout(context.Background(), cfg.ReqTimeout())
+	_, err := srv.Range(ctx, &pb.RangeRequest{KeysOnly: true, Limit: 1, Serializable: serializable})
+	cancel()
+	if err != nil && err != auth.ErrUserEmpty && err != auth.ErrPermissionDenied {
+		h.Health = "false"
+		h.Reason = fmt.Sprintf("RANGE ERROR:%s", err)
+		lg.Warn("serving /health false; Range fails", zap.Error(err))
+		return h
+	}
+	lg.Debug("serving /health true")
+	return h
+}