Spring Cloud Gateway 使用 Kubernetes 作为服务发现

曾经终败给现在 2022-11-17 14:37 221阅读 0赞

# Spring Cloud Gateway 使用 Kubernetes 作为服务发现 #

Spring Cloud Gateway 作为网关，通过用于执行一些通用逻辑后做请求转发，后端可能涉及到多个服务，每个服务又有多个实例，调用服务实例就需要动态的更新，可以通过注册中心来实现，如果部署在K8S集群中，可以直接使用K8S实现服务发现

## 应用 ##

### Gateway ###

#### 添加依赖 ####

*  build.gradle

plugins { 
        id 'org.springframework.boot' version '2.2.6.RELEASE'
        id 'io.spring.dependency-management' version '1.0.9.RELEASE'
        id 'java'
    }
    
    ext { 
        set('springCloudVersion', "Hoxton.SR1")
        set('springKubernetesVersion', "1.1.2.RELEASE")
    }
    
    dependencies { 
        implementation 'org.springframework.cloud:spring-cloud-starter-gateway'
        implementation 'org.springframework.cloud:spring-cloud-kubernetes-discovery'
        implementation 'org.springframework.boot:spring-boot-starter-actuator'
       
        testImplementation('org.springframework.boot:spring-boot-starter-test') { 
            exclude group: 'org.junit.vintage', module: 'junit-vintage-engine'
        }
    }
    
    dependencyManagement { 
        imports { 
            mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
            mavenBom "org.springframework.cloud:spring-cloud-kubernetes-dependencies:${springKubernetesVersion}"
        }
    }

*  如果是需要客户端实现负载均衡，依赖是

implementation 'org.springframework.cloud:spring-cloud-starter-gateway'
        implementation 'org.springframework.cloud:spring-cloud-starter-kubernetes-all'
        implementation 'org.springframework.cloud:spring-cloud-starter-netflix-ribbon'

#### 添加路由配置 ####

*  bootstrap.yaml

spring:
      cloud:
        kubernetes:
          discovery:
            catalogServicesWatchDelay: 5000
          client:
            master-url: https://kubernetes.docker.internal:6443
            ca-cert-data: xxx
            namespace: default

*  applicaiton.yaml

spring:
      application.name: gateway
      cloud:
        gateway:
          discovery:
            locator:
              enabled: true
              url-expression: "'http://'+serviceId+':'+port"
              lower-case-service-id: true
              
    management:
      endpoints:
        web:
          exposure:
            include: '*'

配置 `url-expression` 目的是为了在转发的时候直接转发到 Kubernetes 中相应的 Service 上去，默认的表达式为 `"'lb://'+serviceId"`，这种适用于通过 Consul 或者 Eureka，最终是根据服务的IP和端口访问，`spring-cloud-kubernetes`没有实现`com.netflix.loadbalancer.AbstractServerList`，所以不会进行IP转换，最终是通过服务名称查找Service 实现调用，所以不需要负载均衡

*  如果是客户端实现负载均衡，则不需要指定`"'http://'+serviceId+':'+port"`

### 部署 ###

通过 Gateway 调用后端的 API 应用，该应用提供 REST 接口

#### 部署后端API应用 ####

*  api.yaml

apiVersion: v1
    kind: Service
    metadata:
      name: api
      namespace: default
      labels:
        app: api
    spec:
      type: ClusterIP
      ports:
        - port: 8080
      selector:
        app: api
    
    ---
    
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      labels:
        app: api
      name: api
      namespace: default
    spec:
      replicas: 1
      selector:
        matchLabels:
          app: api
      template:
        metadata:
          labels:
            app: api
        spec:
          containers:
            - name: api
              image: registry.cn-qingdao.aliyuncs.com/hellowoodes/api:1.0.0
              imagePullPolicy: IfNotPresent
              ports:
                - containerPort: 8080
                  name: http
                  protocol: TCP

*  部署 API 服务

kubectl apply -f api.yaml

#### 部署 Gateway ####

*  gateway.yaml

apiVersion: v1
    kind: Service
    metadata:
      name: gateway
      namespace: default
      labels:
        app: gateway
    spec:
      type: NodePort
      ports:
        - port: 8080
          nodePort: 30080
      selector:
        app: gateway
    
    ---
    
    apiVersion: apps/v1
    kind: Deployment
    metadata:
      labels:
        app: gateway
      name: gateway
      namespace: default
    spec:
      replicas: 1
      selector:
        matchLabels:
          app: gateway
      template:
        metadata:
          labels:
            app: gateway
        spec:
          containers:
            - name: gateway
              image: registry.cn-qingdao.aliyuncs.com/hellowoodes/api-gateway:1.0.6
              imagePullPolicy: IfNotPresent
              ports:
                - containerPort: 8080
                  name: http
                  protocol: TCP

*  部署 gateway 服务

kubectl apply -f gateway.yaml

### 测试 ###

*  查询所有路由

http get localhost:30080/actuator/gateway/routes

*  请求 API 服务接口

http get localhost:30080/api/hello

这里会根据 `api`这个path 查找名为 `api`的 Service，然后调用 `http://api:8080/hello`，这个接口返回hostname，也就是pod的名称

*  负载均衡

启动多个 API 服务实例

kubectl scale --replicas=2 deploy/api

待服务启动后多次调用`http://localhost:30080/api/hello`，返回的pod名称会变化，说明负载均衡生效

## 参考 ##

*  [how-to-set-up-spring-cloud-gateway-application-so-it-can-use-the-service-discove][]
 *  [spring-cloud-kubernetes-spring-cloud-gateway-unable-to-find-instance-for-k8s][]
 *  [salaboy/s1p\_gateway][salaboy_s1p_gateway]
 *  [why use ribbon in k8s?How about clusterIp?][why use ribbon in k8s_How about clusterIp]
 *  [spring-cloud-starter-consul-discovery depends on spring-cloud-starter-netflix-ribbon][]
 *  [What’s causing: forbidden: User “system:anonymous” in some Cloud Providers][What_s causing_ forbidden_ User _system_anonymous_ in some Cloud Providers]

[how-to-set-up-spring-cloud-gateway-application-so-it-can-use-the-service-discove]: https://stackoverflow.com/questions/56170511/how-to-set-up-spring-cloud-gateway-application-so-it-can-use-the-service-discove
[spring-cloud-kubernetes-spring-cloud-gateway-unable-to-find-instance-for-k8s]: https://stackoverflow.com/questions/57594228/spring-cloud-kubernetes-spring-cloud-gateway-unable-to-find-instance-for-k8s
[salaboy_s1p_gateway]: https://github.com/salaboy/s1p_gateway
[why use ribbon in k8s_How about clusterIp]: https://github.com/spring-cloud/spring-cloud-kubernetes/issues/541
[spring-cloud-starter-consul-discovery depends on spring-cloud-starter-netflix-ribbon]: https://github.com/spring-cloud/spring-cloud-consul/issues/562
[What_s causing_ forbidden_ User _system_anonymous_ in some Cloud Providers]: https://github.com/kubernetes-sigs/apiserver-builder-alpha/issues/225