> For the complete documentation index, see [llms.txt](https://darren.gitbook.io/project/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://darren.gitbook.io/project/gai-nian-yu-yuan-li/ji-qun-zi-yuan-dui-xiang/ingress.md).
# Autoscaling
Horizontal Pod Autoscaling (HPA) 可以根据 CPU 使用率或应用自定义 metrics 自动扩展 Pod 数量（支持 replication controller、deployment 和 replica set ）。
* 控制管理器每隔 30s（可以通过 `--horizontal-pod-autoscaler-sync-period` 修改）查询 metrics 的资源使用情况
* 支持三种 metrics 类型
* 预定义 metrics（比如 Pod 的 CPU）以利用率的方式计算
* 自定义的 Pod metrics，以原始值（raw value）的方式计算
* 自定义的 object metrics
* 支持两种 metrics 查询方式：Heapster 和自定义的 REST API
* 支持多 metrics
注意：
* 本章是关于 Pod 的自动扩展，而 Node 的自动扩展请参考 [Cluster AutoScaler](https://kubernetes.feisky.xyz/bu-shu-pei-zhi/index-1/cluster-autoscaler)。
* 在使用 HPA 之前需要 **确保已部署好** [**metrics-server**](https://kubernetes.feisky.xyz/bu-shu-pei-zhi/index-1/metrics)。
## API 版本对照表
| Kubernetes 版本 | autoscaling API 版本 | 支持的 metrics |
| ------------- | ------------------- | ----------- |
| v1.5+ | autoscaling/v1 | CPU |
| v1.6+ | autoscaling/v2beta1 | Memory及自定义 |
## 示例
```
# 创建 pod 和 service
$ kubectl run php-apache --image=k8s.gcr.io/hpa-example --requests=cpu=200m --expose --port=80
service "php-apache" created
deployment "php-apache" created
# 创建 autoscaler
$ kubectl autoscale deployment php-apache --cpu-percent=50 --min=1 --max=10
deployment "php-apache" autoscaled
$ kubectl get hpa
NAME REFERENCE TARGET MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache/scale 0% / 50% 1 10 1 18s
# 增加负载
$ kubectl run -i --tty load-generator --image=busybox /bin/sh
Hit enter for command prompt
$ while true; do wget -q -O- http://php-apache.default.svc.cluster.local; done
# 过一会就可以看到负载升高了
$ kubectl get hpa
NAME REFERENCE TARGET CURRENT MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache/scale 305% / 50% 305% 1 10 1 3m
# autoscaler 将这个 deployment 扩展为 7 个 pod
$ kubectl get deployment php-apache
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
php-apache 7 7 7 7 19m
# 删除刚才创建的负载增加 pod 后会发现负载降低，并且 pod 数量也自动降回 1 个
$ kubectl get hpa
NAME REFERENCE TARGET MINPODS MAXPODS REPLICAS AGE
php-apache Deployment/php-apache/scale 0% / 50% 1 10 1 11m
$ kubectl get deployment php-apache
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
php-apache 1 1 1 1 27m
```
## 自定义 metrics
使用方法
* 控制管理器开启 `--horizontal-pod-autoscaler-use-rest-clients`
* 控制管理器配置的 `--master` 或者 `--kubeconfig`
* 在 API Server Aggregator 中注册自定义的 metrics API，如 和
> 注：可以参考 [k8s.io/metics](https://github.com/kubernetes/metrics) 开发自定义的 metrics API server。
比如 HorizontalPodAutoscaler 保证每个 Pod 占用 50% CPU、1000pps 以及 10000 请求 / s：
HPA 示例
```
apiVersion: autoscaling/v1
kind: HorizontalPodAutoscaler
metadata:
name: php-apache
namespace: default
spec:
scaleTargetRef:
apiVersion: apps/v1beta1
kind: Deployment
name: php-apache
minReplicas: 1
maxReplicas: 10
metrics:
- type: Resource
resource:
name: cpu
targetAverageUtilization: 50
- type: Pods
pods:
metricName: packets-per-second
targetAverageValue: 1k
- type: Object
object:
metricName: requests-per-second
target:
apiVersion: extensions/v1beta1
kind: Ingress
name: main-route
targetValue: 10k
status:
observedGeneration: 1
lastScaleTime:
currentReplicas: 1
desiredReplicas: 1
currentMetrics:
- type: Resource
resource:
name: cpu
currentAverageUtilization: 0
currentAverageValue: 0
```
## 状态条件
v1.7+ 可以在客户端中看到 Kubernetes 为 HorizontalPodAutoscaler 设置的状态条件 `status.conditions`，用来判断 HorizontalPodAutoscaler 是否可以扩展（AbleToScale）、是否开启扩展（ScalingActive）以及是否受到限制（ScalingLimitted）。
```
$ kubectl describe hpa cm-test
Name: cm-test
Namespace: prom
Labels:
Annotations:
CreationTimestamp: Fri, 16 Jun 2017 18:09:22 +0000
Reference: ReplicationController/cm-test
Metrics: (current / target)
"http_requests" on pods: 66m / 500m
Min replicas: 1
Max replicas: 4
ReplicationController pods: 1 current / 1 desired
Conditions:
Type Status Reason Message
---- ------ ------ -------
AbleToScale True ReadyForNewScale the last scale time was sufficiently old as to warrant a new scale
ScalingActive True ValidMetricFound the HPA was able to successfully calculate a replica count from pods metric http_requests
ScalingLimited False DesiredWithinRange the desired replica count is within the acceptible range
Events:
```
## HPA 最佳实践
* 为容器配置 CPU Requests
* HPA 目标设置恰当，如设置 70% 给容器和应用预留 30% 的余量
* 保持 Pods 和 Nodes 健康（避免 Pod 频繁重建）
* 保证用户请求的负载均衡
* 使用 `kubectl top node` 和 `kubectl top pod` 查看资源使用情况
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://darren.gitbook.io/project/gai-nian-yu-yuan-li/ji-qun-zi-yuan-dui-xiang/ingress.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.