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Access Services by using an ALB Ingress

Application Load Balancer (ALB) provides Ingresses that allow you to access Services. ALB Ingresses are suitable for handling traffic fluctuations.

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

  • A kubectl client is connected to your cluster.
  • The ALB Ingress controller is installed. For more information, see Compilation and deployment.

Precautions

  • The version of Kubernetes is 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.

Step 1: Create an AlbConfig object

  1. 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. 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.

  2. Run the following command to create an AlbConfig object:

    kubectl apply -f alb-test.yaml

    Expected output:

    AlbConfig.alibabacloud.com/alb-demo created

  3. Create an alb.yaml file that contains the following content:

    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

  4. 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

  1. 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

  2. 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

  3. 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

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

    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: Prefix
        backend:
          service:
            name: tea-svc
            port:
              number: 80
      # Configure a context path.
      - path: /coffee
        pathType: Prefix
        backend:
          service:
            name: coffee-svc
            port:
              number: 80

  2. 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

  3. Run the following command to query the IP 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 IP 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 IP 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