Access Services by using an ALB Ingress - Container Service for Kubernetes

ALB Ingresses provide access to Services by using Application Load Balancer (ALB). ALB Ingresses are suitable for handling traffic fluctuations. This topic describes how to use an ALB Ingress to expose Services in a Container Service for Kubernetes (ACK) cluster.

Background information

An Ingress provides a collection of rules that manage external access to Services in a Kubernetes cluster. You can configure forwarding rules to assign different externally-accessible URLs to different Services. However, NGINX Ingresses and Layer 4 Server Load Balancer (SLB) Ingresses cannot meet the requirements of cloud-native applications, such as complex routing, multiple application layer protocols support (such as QUIC), and balancing of heavy traffic loads at Layer 7.

Prerequisites

The ALB Ingress controller is installed.
- You can install the ALB Ingress controller when you create a cluster by setting the Ingress parameter to ALB Ingress on the Component Configurations wizard page.
- If you use an existing cluster that does not have the ALB Ingress controller installed, refer to Manage system components and install the ALB Ingress controller in the cluster.
If you want to expose Services in an ACK dedicated cluster by using an ALB Ingress, you must grant the required permissions to the ALB Ingress controller that is installed in the cluster before you deploy the Services. For more information, see Grant permissions to the ALB Ingress controller.
A kubectl client is connected to the cluster. For more information, see Obtain the kubeconfig file of a cluster and use kubectl to connect to the cluster.

Precautions

The version of Kubernetes must be 1.18 or later.
If you use the Flannel network plug-in, the backend Services of the ALB Ingress must be of the NodePort or LoadBalancer type.
The names of AlbConfig objects, namespaces, Ingresses, and Services cannot start with aliyun.

Step 1: Create an AlbConfig object

Create a file named alb-test.yaml and copy the following content to the file. The file is used to create an AlbConfig Object.

apiVersion: alibabacloud.com/v1
kind: AlbConfig
metadata:
  name: alb-demo
spec:
  config:
    name: alb-test
    addressType: Internet
    zoneMappings:
    - vSwitchId: vsw-uf6ccg2a9g71hx8go****
    - vSwitchId: vsw-uf6nun9tql5t8nh15****


Parameter	Description
spec.config.name	The name of the ALB instance. This parameter is optional.
spec.config.addressType	The type of IP address that the ALB instance uses to provide services. This parameter is required. Valid values: Internet: The ALB instance uses a public IP address. The domain name of the Ingress is resolved to the public IP address of the ALB instance. Therefore, the ALB instance is accessible over the Internet. This is the default value. Intranet: The ALB instance uses a private IP address. The domain name of the Ingress is resolved to the private IP address of the ALB instance. Therefore, the ALB instance is accessible only within the virtual private cloud (VPC) where the ALB instance is deployed.
spec.config.zoneMappings	The IDs of the vSwitches that are used by the ALB Ingress. You must specify at least two vSwitch IDs and the vSwitches must be deployed in different zones. The zones of the vSwitches must be supported by ALB Ingresses. This parameter is required. For more information about the regions and zones that are supported by ALB Ingresses, see Supported regions and zones.

Run the following command to create an AlbConfig object:

kubectl apply -f alb-test.yaml

Expected output:

AlbConfig.alibabacloud.com/alb-demo created

Create a file named alb.yaml and copy the following content to the file:

Clusters that run Kubernetes versions earlier than 1.19 Clusters that run Kubernetes 1.19 and later versions

apiVersion: networking.k8s.io/v1beta1
kind: IngressClass
metadata:
  name: alb
spec:
  controller: ingress.k8s.alibabacloud/alb
  parameters:
    apiGroup: alibabacloud.com
    kind: AlbConfig
    name: alb-demo

apiVersion: networking.k8s.io/v1
kind: IngressClass
metadata:
  name: alb
spec:
  controller: ingress.k8s.alibabacloud/alb
  parameters:
    apiGroup: alibabacloud.com
    kind: AlbConfig
    name: alb-demo

Run the following command to create an IngressClass:
```
kubectl apply -f alb.yaml
```
Expected output:
```
ingressclass.networking.k8s.io/alb created
```

Step 2: Deploy applications

Create a cafe-service.yaml file and copy the following content to the file. The file is used to deploy two Deployments named coffee and tea and two Services named coffee and tea.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: coffee
spec:
  replicas: 2
  selector:
    matchLabels:
      app: coffee
  template:
    metadata:
      labels:
        app: coffee
    spec:
      containers:
      - name: coffee
        image: registry.cn-hangzhou.aliyuncs.com/acs-sample/nginxdemos:latest
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: coffee-svc
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
  selector:
    app: coffee
  type: NodePort
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: tea
spec:
  replicas: 1
  selector:
    matchLabels:
      app: tea
  template:
    metadata:
      labels:
        app: tea
    spec:
      containers:
      - name: tea
        image: registry.cn-hangzhou.aliyuncs.com/acs-sample/nginxdemos:latest
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: tea-svc
spec:
  ports:
  - port: 80
    targetPort: 80
    protocol: TCP
  selector:
    app: tea
  type: NodePort

Run the following command to deploy the Deployments and Services:

kubectl apply -f cafe-service.yaml

Expected output:

deployment "coffee" created
service "coffee-svc" created
deployment "tea" created
service "tea-svc" created

Run the following command to query the status of the Services that you created:

kubectl get svc,deploy

Expected output:

NAME             TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
coffee-svc   NodePort    172.16.231.169   <none>        80:31124/TCP   6s
tea-svc      NodePort    172.16.38.182    <none>        80:32174/TCP   5s
NAME            DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
deploy/coffee   2         2         2            2           1m
deploy/tea      1         1         1            1           1m

Step 3: Configure an Ingress

Create a cafe-ingress.yaml and copy the following content to the file:

Clusters that run Kubernetes versions earlier than 1.19 Clusters that run Kubernetes 1.19 and later versions

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: cafe-ingress
spec:
  ingressClassName: alb
  rules:
   - host: demo.domain.ingress.top
     http:
      paths:
      # Configure a context path. 
      - path: /tea
        backend:
          serviceName: tea-svc
          servicePort: 80
      # Configure a context path. 
      - path: /coffee
        backend:
          serviceName: coffee-svc
          servicePort: 80

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: cafe-ingress 
spec:
  ingressClassName: alb
  rules:
   - host: demo.domain.ingress.top
     http:
      paths:
      # Configure a context path.
      - path: /tea
        pathType: ImplementationSpecific
        backend:
          service:
            name: tea-svc
            port:
              number: 80
      # Configure a context path.
      - path: /coffee
        pathType: ImplementationSpecific
        backend:
          service:
            name: coffee-svc
            port: 
              number: 80

Run the following command to configure an externally-accessible domain name and a path for the coffee and tea Services separately:
```
kubectl apply -f cafe-ingress.yaml
```
Expected output:
```
ingress "cafe-ingress" created
```

Run the following command to query the address of the ALB instance:

kubectl get ing

Expected output:

NAME           CLASS    HOSTS                         ADDRESS                                               PORTS   AGE
cafe-ingress   alb      demo.domain.ingress.top       alb-m551oo2zn63yov****.cn-hangzhou.alb.aliyuncs.com   80      50s

Step 4: Access the Services

After you obtain the address of the ALB instance, use the CLI to access the coffee Service:

curl -H Host:demo.domain.ingress.top http://alb-lhwdm5c9h8lrcm****.cn-hangzhou.alb.aliyuncs.com/coffee

After you obtain the address of the ALB instance, use the CLI to access the tea Service:

curl -H Host:demo.domain.ingress.top http://alb-lhwdm5c9h8lrcm****.cn-hangzhou.alb.aliyuncs.com/tea