metrics: add EMA cpu usage (#39995)

close #40029

metrics/BUILD.bazel

@@ -13,6 +13,7 @@ go_library(
         "meta.go",
         "metrics.go",
         "owner.go",
+        "resourcemanager.go",
         "server.go",
         "session.go",
         "sli.go",

metrics/metrics.go

@@ -215,6 +215,8 @@ func RegisterMetrics() {
 	prometheus.MustRegister(TTLJobStatus)
 	prometheus.MustRegister(TTLPhaseTime)
 
+	prometheus.MustRegister(EMACPUUsageGauge)
+
 	tikvmetrics.InitMetrics(TiDB, TiKVClient)
 	tikvmetrics.RegisterMetrics()
 	tikvmetrics.TiKVPanicCounter = PanicCounter // reset tidb metrics for tikv metrics

metrics/resourcemanager.go

@@ -0,0 +1,27 @@
+// Copyright 2022 PingCAP, Inc.
+//
+// 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 metrics
+
+import "github.com/prometheus/client_golang/prometheus"
+
+var (
+	// EMACPUUsageGauge means exponential moving average of CPU usage
+	EMACPUUsageGauge = prometheus.NewGauge(prometheus.GaugeOpts{
+		Namespace: "tidb",
+		Subsystem: "rm",
+		Name:      "ema_cpu_usage",
+		Help:      "exponential moving average of CPU usage",
+	})
+)

resourcemanager/rm.go

@@ -43,5 +43,5 @@ func (r *ResourceManager) Start() {
 // Stop is to stop resource manager
 func (r *ResourceManager) Stop() {
 	r.cpuObserver.Stop()
-	r.wg.Done()
+	r.wg.Wait()
 }

util/cpu/BUILD.bazel

@@ -6,6 +6,7 @@ go_library(
     importpath = "github.com/pingcap/tidb/util/cpu",
     visibility = ["//visibility:public"],
     deps = [
+        "//metrics",
         "//util/cgroup",
         "//util/mathutil",
         "@com_github_cloudfoundry_gosigar//:gosigar",

util/cpu/cpu.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/cloudfoundry/gosigar"
 	"github.com/pingcap/log"
+	"github.com/pingcap/tidb/metrics"
 	"github.com/pingcap/tidb/util/cgroup"
 	"github.com/pingcap/tidb/util/mathutil"
 	"go.uber.org/atomic"
@@ -66,6 +67,7 @@ func (c *Observer) Start() {
 				curr := c.observe()
 				c.cpu.Add(curr)
 				cpuUsage.Store(c.cpu.Get())
+				metrics.EMACPUUsageGauge.Set(c.cpu.Get())
 			case <-c.exit:
 				return
 			}