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health.go
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health.go
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// 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"
"github.com/prometheus/client_golang/prometheus"
"go.uber.org/zap"
pb "go.etcd.io/etcd/api/v3/etcdserverpb"
"go.etcd.io/etcd/client/pkg/v3/types"
"go.etcd.io/etcd/server/v3/auth"
"go.etcd.io/etcd/server/v3/config"
"go.etcd.io/raft/v3"
)
const (
PathHealth = "/health"
PathProxyHealth = "/proxy/health"
)
type ServerHealth interface {
Alarms() []*pb.AlarmMember
Leader() types.ID
Range(context.Context, *pb.RangeRequest) (*pb.RangeResponse, error)
Config() config.ServerConfig
}
// 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 ServerHealth, 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 ServerHealth, 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 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
}