部署一个应用

metrics-app.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: metrics-app
  name: metrics-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: metrics-app
  template:
    metadata:
      labels:
        app: metrics-app
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "80"
        prometheus.io/path: "/metrics"
    spec:
      containers:
      - image: lizhenliang/metrics-app
        name: metrics-app
        ports:
        - name: web
          containerPort: 80
        resources:
          requests:
            cpu: 200m
            memory: 256Mi
        readinessProbe:
          httpGet:
            path: /
            port: 80
          initialDelaySeconds: 3
          periodSeconds: 5
        livenessProbe:
          httpGet:
            path: /
            port: 80
          initialDelaySeconds: 3
          periodSeconds: 5
---
apiVersion: v1
kind: Service
metadata:
  name: metrics-app
  labels:
    app: metrics-app
spec:
  ports:
  - name: web
    port: 80
    targetPort: 80
  selector:
    app: metrics-app

该metrics-app暴露了一个Prometheus指标接口，可以通过访问service看到，http_requests_per_second 就是 QPS（每秒请求数） 指标数据：

[root ~]# curl 10.106.34.139/metrics
# HELP http_requests_total The amount of requests in total
# TYPE http_requests_total counter
http_requests_total 579981
# HELP http_requests_per_second The amount of requests per second the latest ten seconds
# TYPE http_requests_per_second gauge
http_requests_per_second 0.5

用SeviceMonitor暴露自定义指标

SeviceMonitor_test.yaml

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: monitor-metrics-app
  namespace: default
  labels:
    app: metrics-app  #Prometheus所选择的标签
spec:
  namespaceSelector:  #监控的pod所在名称空间
    matchNames:
    - default
  selector:  #选择监控endpoint的标签
    matchLabels:
      app: metrics-app
  endpoints:
  - port: web #service中对应的端口名称

使用这个命令获取数据

kubectl get --raw /apis/custom.metrics.k8s.io/v1beta1/namespaces/default/pods/*/http_requests_per_second | jq .

{
  "kind": "MetricValueList",
  "apiVersion": "custom.metrics.k8s.io/v1beta1",
  "metadata": {
    "selfLink": "/apis/custom.metrics.k8s.io/v1beta1/namespaces/default/pods/%2A/http_requests_per_second"
  },
  "items": [
    {
      "describedObject": {
        "kind": "Pod",
        "namespace": "default",
        "name": "metrics-app-5d464b6b8b-6lnjw",
        "apiVersion": "/v1"
      },
      "metricName": "http_requests_per_second",
      "timestamp": "2021-11-05T03:20:55Z",
      "value": "600m",
      "selector": null
    },
    {
      "describedObject": {
        "kind": "Pod",
        "namespace": "default",
        "name": "metrics-app-5d464b6b8b-kbrfc",
        "apiVersion": "/v1"
      },
      "metricName": "http_requests_per_second",
      "timestamp": "2021-11-05T03:20:55Z",
      "value": "600m",
      "selector": null
    },
    {
      "describedObject": {
        "kind": "Pod",
        "namespace": "default",
        "name": "metrics-app-5d464b6b8b-xclgr",
        "apiVersion": "/v1"
      },
      "metricName": "http_requests_per_second",
      "timestamp": "2021-11-05T03:20:55Z",
      "value": "500m",
      "selector": null
    }
  ]
}

创建HPA策略：

# vi app-hpa-v2.yml
apiVersion: autoscaling/v2beta2
kind: HorizontalPodAutoscaler
metadata:
  name: metrics-app-hpa 
  namespace: default
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: metrics-app
  minReplicas: 1
  maxReplicas: 10
  metrics:
  - type: Pods
    pods:
      metric:
        name: http_requests_per_second
      target:
        type: AverageValue
        averageValue: 800m   # 800m 即0.8个/秒

成功

[root@k8s-master01 hpa]# kubectl get hpa
NAME              REFERENCE                TARGETS     MINPODS   MAXPODS   REPLICAS   AGE
metrics-app-hpa   Deployment/metrics-app   566m/800m   1         10        3          14d

压测

yum -y install httpd-tools

ab -n 100000 -c 100  http://10.1.181.193/metrics

查看HPA状态：

kubectl get hpa
kubectl describe hpa metrics-app-hpa