api/etcdhttp: serve error information in '/health'

Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>

e2e/ctl_v3_alarm_test.go

@@ -53,7 +53,7 @@ func alarmTest(cx ctlCtx) {
 	}
 
 	// '/health' handler should return 'false'
-	if err := cURLGet(cx.epc, cURLReq{endpoint: "/health", expected: `{"health": "false"}`}); err != nil {
+	if err := cURLGet(cx.epc, cURLReq{endpoint: "/health", expected: `{"health": "false", "errors": ["NOSPACE"]}`}); err != nil {
 		cx.t.Fatalf("failed get with curl (%v)", err)
 	}
 

etcdserver/api/etcdhttp/metrics.go

@@ -21,6 +21,7 @@ import (
 	"time"
 
 	"github.com/coreos/etcd/etcdserver"
+	"github.com/coreos/etcd/etcdserver/api/v3rpc/rpctypes"
 	"github.com/coreos/etcd/etcdserver/etcdserverpb"
 	"github.com/coreos/etcd/raft"
 
@@ -57,34 +58,56 @@ func newHealthHandler(srv *etcdserver.EtcdServer) http.HandlerFunc {
 			return
 		}
 		h := checkHealth(srv)
-		d := []byte(fmt.Sprintf(`{"health": "%v"}`, h.Health))
+		d := h.marshal()
 		if !h.Health {
-			http.Error(w, string(d), http.StatusServiceUnavailable)
+			http.Error(w, d, http.StatusServiceUnavailable)
 			return
 		}
 		w.WriteHeader(http.StatusOK)
-		w.Write(d)
+		w.Write([]byte(d))
 	}
 }
 
 type health struct {
-	Health bool `json:"health"`
+	Health bool     `json:"health"`
+	Errors []string `json:"errors"`
+}
+
+func (h health) marshal() string {
+	s := fmt.Sprintf(`{"health": "%v"`, h.Health)
+	if len(h.Errors) > 0 {
+		ss := []string{}
+		for _, v := range h.Errors {
+			ss = append(ss, fmt.Sprintf("%q", v))
+		}
+		s += fmt.Sprintf(`, "errors": %v`, ss)
+	}
+	s += "}"
+	return s
 }
 
 func checkHealth(srv *etcdserver.EtcdServer) health {
 	h := health{Health: false}
-	if len(srv.Alarms()) > 0 {
-		// TODO: provide alarm lists
+
+	as := srv.Alarms()
+	if len(as) > 0 {
+		for _, v := range as {
+			h.Errors = append(h.Errors, v.Alarm.String())
+		}
 		return h
 	}
 
 	if uint64(srv.Leader()) == raft.None {
+		h.Errors = append(h.Errors, rpctypes.ErrNoLeader.Error())
 		return h
 	}
 
 	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
 	_, err := srv.Do(ctx, etcdserverpb.Request{Method: "QGET"})
 	cancel()
+	if err != nil {
+		h.Errors = append(h.Errors, err.Error())
+	}
 
 	h.Health = err == nil
 	return h