本文分享自华为云社区《根据Nginx Ingress指标对指定后端进行HPA》，作者： 可以交个朋友。
背景
生产场景下，Nginx Ingress的流量会通过域名和path路径最终转发至不同的应用，而有时候cpu和内存并不是nginx的性能瓶颈，此时可以基于nginx_ingress_controller_requests指标，为其对应的应用配置HPA，以实现基于不同域名和path的请求量弹性指定后端工作负载
简介
环境准备
- nginx-ingress已部署
- 云原生监控插件kube-prometheus-stack已安装（server模式)，插件默认监控nginx-ingress，开源环境请自行配置监控。
- 已配置kubectl命令或使用cloudshell
注意：由于HPA规则中scaleTargetRef和describedObject两个字段都无法指定命名空间，所以指标来源、HPA和弹性目标需在同一命名空间，而nginx-ingress和业务工作负载一般处在不同命名空间；本次方案采用external类型的HPA，可以忽略指标来源的命名空间
操作步骤
创建演示需要的弹性目标工作负载，service以及ingress
apiVersion: apps/v1
kind: Deployment
metadata:
name: test-hpa
labels:
app: test-app
spec:
replicas: 1
selector:
matchLabels:
app: test-app
template:
metadata:
labels:
app: test-app
spec:
containers:
- image: skto/sample-app:v2
name: metrics-provider
ports:
- name: http
containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
name: test-app
namespace: default
labels:
app: test-app
spec:
ports:
- port: 8080
name: http
protocol: TCP
targetPort: 8080
selector:
app: test-app
type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: sample-app
labels:
app: sample-app
spec:
replicas: 1
selector:
matchLabels:
app: sample-app
template:
metadata:
labels:
app: sample-app
spec:
containers:
- image: skto/sample-app:v2
name: metrics-provider
ports:
- name: http
containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
name: sample-app
namespace: default
labels:
app: sample-app
spec:
ports:
- port: 80
name: http
protocol: TCP
targetPort: 8080
selector:
app: sample-app
type: ClusterIP
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: test-ingress
namespace: default
spec:
ingressClassName: nginx
rules:
- host: test.example.com
http:
paths:
- backend:
service:
name: sample-app
port:
number: 80
path: /
pathType: ImplementationSpecific
- backend:
service:
name: test-app
port:
number: 8080
path: /home
pathType: ImplementationSpecific
分别查询test.example.com/和test.example.com/home的nginx_ingress_controller_requests指标，指标正常
创建external类型的apiservices资源；创建后apiservices的状态为false是正常现象，添加externalRules后状态变为true
apiVersion: apiregistration.k8s.io/v1
kind: APIService
metadata:
name: v1beta1.external.metrics.k8s.io
spec:
group: external.metrics.k8s.io
groupPriorityMinimum: 100
insecureSkipTLSVerify: true
service: #指定prometheus-adapter对应的service，华为CCE插件中adapter名称为custom-metrics-apiserver
name: custom-metrics-apiserver
namespace: monitoring
port: 443
version: v1beta1
versionPriority: 100
将externalRules规则添加到adapter的configmap中，修改后需要重启prometheus-adapter服务
kubectl -n monitoring edit configmap user-adapter-config
externalRules:
- metricsQuery: sum(rate(<<.Series>>{<<.LabelMatchers>>}[2m])) by (<<.GroupBy>>)
name:
as: ${1}_per_second
matches: ^(.*)
resources:
namespaced: false #忽略指标来源的命名空间，该配置不适用rules规则
seriesQuery: nginx_ingress_controller_requests
seriesQuery：原始指标；可以直接写指标名称，也可以使用{labelKey=labelValue}的方式筛选出原始指标
metricsQuery：用PromQL对指标进行筛选汇聚；.Series表示原始指标，.LabelMatchers表示对指标进行标签筛选，hpa中可以配置具体的筛选规则
name：将指标重命名
resources：hpa查询指标时通过api的方式调用，调用路径为：
而resources的作用就是将指标中命名空间标签的值替换路径中的${namespace}，而我们本次方案需要忽略指标来源命名空间。
custom-metrics-apiserver服务重启后需要等待1分钟左右，执行命令查看指标是否正常
kubectl get --raw /apis/external.metrics.k8s.io/v1beta1/namespaces/*/nginx_ingress_controller_requests_per_second
创建HPA规则
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
name: sample-hpa
spec:
scaleTargetRef:
apiVersion: apps/v1
kind: Deployment
name: sample-app
minReplicas: 1
maxReplicas: 10
metrics:
- type: External
external:
metric:
name: nginx_ingress_controller_requests_per_second
selector:
matchLabels: #可以通过该字段对指标进行过滤，这里标签筛选条件会加入到externalRules的<<.LabelMatchers>>中。
exported_service: sample-app #筛选后端服务为sample-app的请求
host: test.example.com #筛选访问域名为test.example.com的请求
target:
type: AverageValue #External指标类型下只支持Value和AverageValue类型的目标值。
averageValue: 30
---
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
name: test-hpa
spec:
scaleTargetRef:
apiVersion: apps/v1
kind: Deployment
name: test-app
minReplicas: 1
maxReplicas: 10
metrics:
- type: External
external:
metric:
name: nginx_ingress_controller_requests_per_second
selector:
matchLabels:
exported_service: test-app
host: test.example.com
target:
type: AverageValue
averageValue: 30
弹性演示
使用命令压测sample-app对应的访问域名和路径，正常触发弹性；请自行配置域名与ELB地址的映射
ab -c 50 -n 5000 http://test.example.com/
用同样的方式压测test-app，正常触发弹性
ab -c 50 -n 5000 http://test.example.com/home
