Question

Kubernetes中不仅支持CPU、内存为指标的HPA，还支持自定义指标的HPA，例如QPS。

本文中使用的yaml文件见manifests/HPA。

设置自定义指标

kubernetes1.6

在kubernetes1.6集群中配置自定义指标的HPA的说明已废弃。

在设置定义指标HPA之前需要先进行如下配置：

• 将heapster的启动参数 --api-server 设置为 true

• 启用custom metric API

• 将kube-controller-manager的启动参数中--horizontal-pod-autoscaler-use-rest-clients设置为true，并指定--master为API server地址，如--master=http://172.20.0.113:8080

在kubernetes1.5以前很容易设置，参考1.6以前版本的kubernetes中开启自定义HPA，而在1.6中因为取消了原来的annotation方式设置custom metric，只能通过API server和kube-aggregator来获取custom metric，因为只有两种方式来设置了，一是直接通过API server获取heapster的metrics，二是部署kube-aggragator来实现。

我们将在kubernetes1.8版本的kubernetes中，使用聚合的API server来实现自定义指标的HPA。

kuberentes1.7+

确认您的kubernetes版本在1.7或以上，修改以下配置：

• 将kube-controller-manager的启动参数中--horizontal-pod-autoscaler-use-rest-clients设置为true，并指定--master为API server地址，如`--master=http://172.20.0.113:8080
• 修改kube-apiserver的配置文件apiserver，增加一条配置--requestheader-client-ca-file=/etc/kubernetes/ssl/ca.pem --requestheader-allowed-names=aggregator --requestheader-extra-headers-prefix=X-Remote-Extra- --requestheader-group-headers=X-Remote-Group --requestheader-username-headers=X-Remote-User --proxy-client-cert-file=/etc/kubernetes/ssl/kubernetes.pem --proxy-client-key-file=/etc/kubernetes/ssl/kubernetes-key.pem，用来配置aggregator的CA证书。

已经内置了apiregistration.k8s.io/v1beta1 API，可以直接定义APIService，如：

apiVersion: apiregistration.k8s.io/v1
kind: APIService
metadata:
  name: v1.custom-metrics.metrics.k8s.io
spec:
  insecureSkipTLSVerify: true
  group: custom-metrics.metrics.k8s.io
  groupPriorityMinimum: 1000
  versionPriority: 5
  service:
    name: api
    namespace: custom-metrics
  version: v1alpha1

部署Prometheus

使用prometheus-operator.yaml文件部署Prometheus operator。

注意：将镜像修改为你自己的镜像仓库地址。

这产生一个自定义的API：http://172.20.0.113:8080/apis/custom-metrics.metrics.k8s.io/v1alpha1，可以通过浏览器访问，还可以使用下面的命令可以检查该API：

$ kubectl get --raw=apis/custom-metrics.metrics.k8s.io/v1alpha1
{"kind":"APIResourceList","apiVersion":"v1","groupVersion":"custom-metrics.metrics.k8s.io/v1alpha1","resources":[{"name":"jobs.batch/http_requests","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"namespaces/http_requests","singularName":"","namespaced":false,"kind":"MetricValueList","verbs":["get"]},{"name":"jobs.batch/up","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"pods/up","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"services/scrape_samples_scraped","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"namespaces/scrape_samples_scraped","singularName":"","namespaced":false,"kind":"MetricValueList","verbs":["get"]},{"name":"pods/scrape_duration_seconds","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"services/scrape_duration_seconds","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"pods/http_requests","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"pods/scrape_samples_post_metric_relabeling","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"jobs.batch/scrape_samples_scraped","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"jobs.batch/scrape_duration_seconds","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"namespaces/scrape_duration_seconds","singularName":"","namespaced":false,"kind":"MetricValueList","verbs":["get"]},{"name":"namespaces/scrape_samples_post_metric_relabeling","singularName":"","namespaced":false,"kind":"MetricValueList","verbs":["get"]},{"name":"services/scrape_samples_post_metric_relabeling","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"services/up","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"pods/scrape_samples_scraped","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"services/http_requests","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"jobs.batch/scrape_samples_post_metric_relabeling","singularName":"","namespaced":true,"kind":"MetricValueList","verbs":["get"]},{"name":"namespaces/up","singularName":"","namespaced":false,"kind":"MetricValueList","verbs":["get"]}]}

参考

• 1.6以前版本的kubernetes中开启自定义HPA
• 1.7版本的kubernetes中启用自定义HPA
• Horizontal Pod Autoscaler Walkthrough
• Kubernetes 1.8: Now with 100% Daily Value of Custom Metrics
• Arbitrary/Custom Metrics in the Horizontal Pod Autoscaler#117