381 lines
8.5 KiB
Markdown
381 lines
8.5 KiB
Markdown
# KEDA HTTP Add-on 自动缩容到 0 配置指南
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本指南说明如何使用 KEDA HTTP Add-on 实现应用在无流量时自动缩容到 0，有访问时自动启动。
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## 前提条件
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1. K3s 集群已安装
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2. KEDA 已安装
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3. KEDA HTTP Add-on 已安装
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4. Traefik 作为 Ingress Controller
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### 检查 KEDA HTTP Add-on 是否已安装
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```bash
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kubectl get pods -n keda | grep http
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```
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应该看到类似输出：
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```
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keda-add-ons-http-controller-manager-xxx 1/1 Running
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keda-add-ons-http-external-scaler-xxx 1/1 Running
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keda-add-ons-http-interceptor-xxx 1/1 Running
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```
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### 如果未安装，执行以下命令安装
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```bash
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helm repo add kedacore https://kedacore.github.io/charts
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helm repo update
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helm install http-add-on kedacore/keda-add-ons-http --namespace keda
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```
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## 配置步骤
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### 1. 准备应用的基础资源
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确保你的应用已经有以下资源：
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- Deployment
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- Service
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- Namespace
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示例：
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```yaml
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apiVersion: v1
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kind: Namespace
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metadata:
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name: myapp
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---
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apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: myapp
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namespace: myapp
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: myapp
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template:
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metadata:
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labels:
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app: myapp
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spec:
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containers:
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- name: myapp
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image: your-image:tag
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ports:
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- containerPort: 80
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---
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apiVersion: v1
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kind: Service
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metadata:
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name: myapp
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namespace: myapp
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spec:
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selector:
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app: myapp
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ports:
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- port: 80
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targetPort: 80
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```
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### 2. 创建 HTTPScaledObject
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这是实现自动缩容到 0 的核心配置。
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```yaml
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apiVersion: http.keda.sh/v1alpha1
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kind: HTTPScaledObject
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metadata:
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name: myapp-http-scaler
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namespace: myapp # 必须与应用在同一个 namespace
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spec:
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hosts:
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- myapp.example.com # 你的域名
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pathPrefixes:
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- / # 匹配的路径前缀
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scaleTargetRef:
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name: myapp # Deployment 名称
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kind: Deployment
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apiVersion: apps/v1
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service: myapp # Service 名称
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port: 80 # Service 端口
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replicas:
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min: 0 # 空闲时缩容到 0
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max: 10 # 最多扩容到 10 个副本
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scalingMetric:
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requestRate:
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granularity: 1s
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targetValue: 100 # 每秒 100 个请求时扩容
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window: 1m
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scaledownPeriod: 300 # 5 分钟（300秒）无流量后缩容到 0
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```
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**重要参数说明：**
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- `hosts`: 你的应用域名
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- `scaleTargetRef.name`: 你的 Deployment 名称
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- `scaleTargetRef.service`: 你的 Service 名称
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- `scaleTargetRef.port`: 你的 Service 端口
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- `replicas.min: 0`: 允许缩容到 0
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- `scaledownPeriod`: 无流量后多久缩容（秒）
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### 3. 创建 Traefik IngressRoute
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**重要：IngressRoute 必须在 keda namespace 中创建**，因为它需要引用 keda namespace 的拦截器服务。
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```yaml
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apiVersion: traefik.io/v1alpha1
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kind: IngressRoute
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metadata:
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name: myapp-ingress
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namespace: keda # 注意：必须在 keda namespace
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spec:
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entryPoints:
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- web # HTTP 入口
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# - websecure # 如果需要 HTTPS，添加这个
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routes:
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- match: Host(`myapp.example.com`) # 你的域名
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kind: Rule
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services:
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- name: keda-add-ons-http-interceptor-proxy
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port: 8080
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```
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**如果需要 HTTPS，添加 TLS 配置：**
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```yaml
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apiVersion: traefik.io/v1alpha1
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kind: IngressRoute
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metadata:
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name: myapp-ingress
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namespace: keda
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spec:
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entryPoints:
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- websecure
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routes:
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- match: Host(`myapp.example.com`)
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kind: Rule
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services:
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- name: keda-add-ons-http-interceptor-proxy
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port: 8080
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tls:
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certResolver: letsencrypt # 你的证书解析器
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```
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### 4. 完整配置文件模板
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将以下内容保存为 `myapp-keda-scaler.yaml`，并根据你的应用修改相应的值：
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```yaml
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---
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# HTTPScaledObject - 实现自动缩容到 0
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apiVersion: http.keda.sh/v1alpha1
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kind: HTTPScaledObject
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metadata:
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name: myapp-http-scaler
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namespace: myapp # 改为你的 namespace
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spec:
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hosts:
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- myapp.example.com # 改为你的域名
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pathPrefixes:
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- /
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scaleTargetRef:
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name: myapp # 改为你的 Deployment 名称
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kind: Deployment
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apiVersion: apps/v1
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service: myapp # 改为你的 Service 名称
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port: 80 # 改为你的 Service 端口
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replicas:
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min: 0
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max: 10
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scalingMetric:
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requestRate:
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granularity: 1s
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targetValue: 100
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window: 1m
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scaledownPeriod: 300 # 5 分钟无流量后缩容
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---
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# Traefik IngressRoute - 路由流量到 KEDA 拦截器
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apiVersion: traefik.io/v1alpha1
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kind: IngressRoute
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metadata:
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name: myapp-ingress
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namespace: keda # 必须在 keda namespace
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spec:
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entryPoints:
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- web
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routes:
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- match: Host(`myapp.example.com`) # 改为你的域名
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kind: Rule
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services:
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- name: keda-add-ons-http-interceptor-proxy
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port: 8080
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```
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### 5. 应用配置
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```bash
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kubectl apply -f myapp-keda-scaler.yaml
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```
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### 6. 验证配置
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```bash
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# 查看 HTTPScaledObject 状态
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kubectl get httpscaledobject -n myapp
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# 应该看到 READY = True
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# NAME TARGETWORKLOAD TARGETSERVICE MINREPLICAS MAXREPLICAS AGE READY
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# myapp-http-scaler apps/v1/Deployment/myapp myapp:80 0 10 10s True
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# 查看 IngressRoute
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kubectl get ingressroute -n keda
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# 查看当前 Pod 数量
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kubectl get pods -n myapp
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```
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## 工作原理
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1. **有流量时**：
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- 用户访问 `myapp.example.com`
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- Traefik 将流量路由到 KEDA HTTP 拦截器
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- 拦截器检测到请求，通知 KEDA 启动 Pod
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- Pod 启动后（5-10秒），拦截器将流量转发到应用
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- 用户看到正常响应（首次访问可能有延迟）
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2. **无流量时**：
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- 5 分钟（scaledownPeriod）无请求后
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- KEDA 自动将 Deployment 缩容到 0
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- 不消耗任何计算资源
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## 常见问题排查
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### 1. 访问返回 404
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**检查 IngressRoute 是否在 keda namespace：**
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```bash
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kubectl get ingressroute -n keda | grep myapp
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```
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如果不在，删除并重新创建：
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```bash
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kubectl delete ingressroute myapp-ingress -n myapp # 删除错误的
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kubectl apply -f myapp-keda-scaler.yaml # 重新创建
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```
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### 2. HTTPScaledObject READY = False
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**查看详细错误信息：**
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```bash
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kubectl describe httpscaledobject myapp-http-scaler -n myapp
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```
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**常见错误：**
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- `workload already managed by ScaledObject`: 删除旧的 ScaledObject
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```bash
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kubectl delete scaledobject myapp-scaler -n myapp
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```
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### 3. Pod 没有自动缩容到 0
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**检查是否有旧的 ScaledObject 阻止缩容：**
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```bash
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kubectl get scaledobject -n myapp
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```
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如果有，删除它：
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```bash
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kubectl delete scaledobject <name> -n myapp
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```
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### 4. 查看 KEDA 拦截器日志
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```bash
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kubectl logs -n keda -l app.kubernetes.io/name=keda-add-ons-http-interceptor --tail=50
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```
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### 5. 测试拦截器是否工作
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```bash
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# 获取拦截器服务 IP
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kubectl get svc keda-add-ons-http-interceptor-proxy -n keda
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# 直接测试拦截器
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curl -H "Host: myapp.example.com" http://<CLUSTER-IP>:8080
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```
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## 调优建议
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### 调整缩容时间
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根据你的应用特点调整 `scaledownPeriod`：
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- **频繁访问的应用**：设置较长时间（如 600 秒 = 10 分钟）
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- **偶尔访问的应用**：设置较短时间（如 180 秒 = 3 分钟）
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- **演示/测试环境**：可以设置很短（如 60 秒 = 1 分钟）
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```yaml
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scaledownPeriod: 600 # 10 分钟
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```
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### 调整扩容阈值
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根据应用负载调整 `targetValue`：
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```yaml
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scalingMetric:
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requestRate:
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targetValue: 50 # 每秒 50 个请求时扩容（更敏感）
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```
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### 调整最大副本数
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```yaml
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replicas:
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min: 0
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max: 20 # 根据你的资源和需求调整
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```
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## 监控和观察
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### 实时监控 Pod 变化
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```bash
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watch -n 2 'kubectl get pods -n myapp'
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```
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### 查看 HTTPScaledObject 事件
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```bash
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kubectl describe httpscaledobject myapp-http-scaler -n myapp
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```
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### 查看 Deployment 副本数变化
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```bash
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kubectl get deployment myapp -n myapp -w
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```
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## 完整示例：navigation 应用
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参考 `navigation-complete.yaml` 文件，这是一个完整的工作示例。
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## 注意事项
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1. **首次访问延迟**：Pod 从 0 启动需要 5-10 秒，用户首次访问会有延迟
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2. **数据库连接**：确保应用能够快速重新建立数据库连接
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3. **会话状态**：不要在 Pod 中存储会话状态，使用 Redis 等外部存储
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4. **健康检查**：配置合理的 readinessProbe，确保 Pod 就绪后才接收流量
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5. **资源限制**：设置合理的 resources limits，避免启动过慢
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## 参考资源
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- KEDA 官方文档: https://keda.sh/
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- KEDA HTTP Add-on: https://github.com/kedacore/http-add-on
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- Traefik IngressRoute: https://doc.traefik.io/traefik/routing/providers/kubernetes-crd/
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