add alarms metrics for server

Signed-off-by: yuzhiquanlong <yuzhiquanlong@gmail.com>

Author: yuzhiquan

server/etcdserver/apply/apply.go

@@ -16,7 +16,6 @@ package apply
 
 import (
 	"context"
-
 	"github.com/coreos/go-semver/semver"
 	pb "go.etcd.io/etcd/api/v3/etcdserverpb"
 	"go.etcd.io/etcd/api/v3/membershippb"
@@ -34,8 +33,10 @@ import (
 	serverstorage "go.etcd.io/etcd/server/v3/storage"
 	"go.etcd.io/etcd/server/v3/storage/backend"
 	"go.etcd.io/etcd/server/v3/storage/mvcc"
+	"strconv"
 
 	"github.com/gogo/protobuf/proto"
+	"github.com/prometheus/client_golang/prometheus"
 	"go.uber.org/zap"
 )
 
@@ -231,12 +232,14 @@ func (a *applierV3backend) Alarm(ar *pb.AlarmRequest) (*pb.AlarmResponse, error)
 			break
 		}
 		resp.Alarms = append(resp.Alarms, m)
+		alarms.With(prometheus.Labels{"server_id": strconv.FormatUint(uint64(types.ID(ar.MemberID)), 10)}).Inc()
 	case pb.AlarmRequest_DEACTIVATE:
 		m := a.alarmStore.Deactivate(types.ID(ar.MemberID), ar.Alarm)
 		if m == nil {
 			break
 		}
 		resp.Alarms = append(resp.Alarms, m)
+		alarms.With(prometheus.Labels{"server_id": strconv.FormatUint(uint64(types.ID(ar.MemberID)), 10)}).Dec()
 	default:
 		return nil, nil
 	}

server/etcdserver/apply/metrics.go

@@ -0,0 +1,31 @@
+// Copyright 2022 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 apply
+
+import "github.com/prometheus/client_golang/prometheus"
+
+var (
+	alarms = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: "etcd_debugging",
+		Subsystem: "server",
+		Name:      "alarms",
+		Help:      "Alarms of every member in cluster.1 for 'server_id' label with current ID.",
+	},
+		[]string{"server_id"})
+)
+
+func init() {
+	prometheus.MustRegister(alarms)
+}