自定义指标HPA
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"]}]}