2018/07/25 更新
1.11版本出于安全原因kubelet的--read-only-port被禁用，需要手动添加。
环境： kubernetes v1.10.2, Weave, Prometheus v2.2.1
需要kube-controller-manager中加上
--horizontal-pod-autoscaler-use-rest-clients=true-
集成prometheus使用了https://github.com/stefanprodan/k8s-prom-hpa
kubectl create -f ./metrics-server
创建HPA命令例
kubectl autoscale deploy qrcode-service --min=1 --max=10 --cpu-percent=20
后使用wrk进行压力测试，几分钟后发现qrcode-service自动扩展了。这里直接贴官方文档：
Starting from v1.6, a cluster operator can mitigate this problem by tuning the global HPA settings exposed as flags for the kube-controller-manager component:
--horizontal-pod-autoscaler-downscale-delay: The value for this option is a duration that specifies how long the autoscaler has to wait before another downscale operation can be performed after the current one has completed. The default value is 5 minutes (5m0s).
--horizontal-pod-autoscaler-upscale-delay: The value for this option is a duration that specifies how long the autoscaler has to wait before another upscale operation can be performed after the current one has completed. The default value is 3 minutes (3m0s).
