How to use an ALB Ingress to expose Services in an ACK cluster - Server Load Balancer

Application Load Balancer (ALB) Ingresses are compatible with NGINX Ingresses and provide improved traffic routing capabilities based on ALB instances. ALB Ingresses support complex routing, automatic certificate discovery, and the HTTP, HTTPS, and QUIC protocols. ALB Ingresses meet the requirements of cloud-native applications for ultra-high elasticity and balancing of heavy traffic loads at Layer 7. You can configure an ALB Ingress in a Container Service for Kubernetes (ACK) cluster to manage traffic. This topic describes how to deploy Services and access the Services by using an ALB Ingress.

Background information

Terms related to ALB Ingresses:

ALB Ingress controller: a Kubernetes component that manages Ingresses. The ALB Ingress controller serves as an entry point in a cluster and routes external traffic to specific Services. The ALB Ingress controller retrieves the changes to Ingresses from the API server and dynamically generates AlbConfigs when the changes are detected. Then, the ALB Ingress controller performs the following operations in sequence: create ALB instances, configure listeners, create Ingress rules, and configure backend server groups.
AlbConfig CRD: Custom resource definitions (CRDs) extend the Kubernetes API and allow you to create custom resources. An AlbConfig corresponds to one ALB instance.
IngressClass: An IngressClass is an attribute of a Kubernetes Ingress that defines the class or identifier of an Ingress controller. IngressClasses allow you to use multiple Ingress controllers in a cluster and specify a controller for each Ingress.
Ingress: An Ingress is a resource object in Kubernetes that defines the forwarding rules and access rules of external traffic. The Ingress controller forwards traffic based on Ingresses. You can configure forwarding rules in ALB Ingresses by using annotations. After the configuration is complete, HTTP/HTTPS requests can be forwarded to the corresponding Services based on the forwarding rules.
Service: In Kubernetes, a Service is an abstract resource object that defines a set of pods that have the same logical function and allows you to access the pods by using a fixed virtual IP address and port.
A Service provides access to an application and allows other applications or services to communicate with backend pods by accessing the virtual IP address and port of the Service. This eliminates the need to obtain the IP address and port of a specific pod. A Service is an abstraction of a backend application that runs on a set of replicated pods.

The following figure shows the relationship between an ALB instance and an ALB Ingress.

ALB Ingress

Limits

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 AlbConfigs, namespaces, Ingresses, and Services cannot start with aliyun.
Earlier NGINX Ingress controller versions cannot recognize the spec: ingressClassName field of an Ingress. If NGINX Ingresses and ALB Ingresses are configured in your ACK cluster, the ALB Ingresses may be reconciled by an earlier version of the NGINX Ingress controller. To avoid this problem, update your NGINX Ingress controller at the earliest opportunity or use annotations to specify the IngressClasses of ALB Ingresses. For more information, see Update the NGINX Ingress controller or Advanced ALB Ingress configurations.

Scenarios

In the following example, two NGINX Services are deployed on four pods. This topic uses the example to describe how to configure an ALB Ingress to forward requests destined for the same domain name but different URL paths.

Frontend request	Forwarded to
`demo.domain.ingress.top/coffee`	`coffee` Service
`demo.domain.ingress.top/tea`	`tea` Service

Prerequisites

An ACK managed cluster or ACK dedicated cluster is created and the cluster runs Kubernetes 1.18 or later. For more information, see Create an ACK dedicated cluster or Create an ACK managed cluster.
The ALB Ingress controller is installed in the cluster. For more information, see Manage the ALB Ingress controller.
Note
If you want to use an ALB Ingress to access Services deployed in an ACK dedicated cluster, you need to first authorize the cluster to access the ALB Ingress controller. For more information, see Authorize an ACK dedicated cluster to access the ALB Ingress controller.
Optional. kubectl is used to connect to the cluster.
- The kubeconfig file of the cluster is obtained and a kubectl client is connected to the cluster.
- Use kubectl on Cloud Shell to manage ACK clusters

Step 1: Deploy backend Services

ACK console

Log on to the ACK console. In the left-side navigation pane, click Clusters.
On the Clusters page, click the name of the cluster that you want to manage and choose Workloads > Deployments in the left-side navigation pane.

Click Create from YAML in the upper-right corner.

Sample Template: Select Custom.

Template: Paste the following code to the code editor. This YAML file is used to deploy two Deployments named coffee and tea, and two Services named coffee-svc and tea-svc.

View YAML content

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: 2
  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

After the configuration is complete, click Create. The Created message appears.
Verify that the Deployments and Services are created:
1. In the left-side navigation pane, choose Workloads > Deployments. The Deployments named coffee and tea are displayed.
2. In the left-side navigation pane, choose Network > Services. The Services named coffee-svc and tea-svc are displayed.

kubectl

Create a file named-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-svc and tea-svc.

View YAML content

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: 2
  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 view the status of the Deployments and Services:

Run the following command to view the status of the Deployments:

kubectl get deployment

Expected output:

NAME                             READY   UP-TO-DATE   AVAILABLE   AGE
coffee                           1/2     2            1           2m26s
tea                              1/1     1            1           2m26s

Run the following command to query the status of the Services:

kubectl get svc

Expected output:

NAME                          TYPE           CLUSTER-IP       EXTERNAL-IP           PORT(S)                 AGE
coffee-svc                    NodePort       172.16.XX.XX     <none>                80:32056/TCP            9m38s
tea-svc                       NodePort       172.16.XX.XX     <none>                80:31696/TCP            9m38s

Step 2: Create an AlbConfig

ACK console

Log on to the ACK console. In the left-side navigation pane, click Clusters.
On the Clusters page, click the name of the cluster that you want to manage and choose Workloads > Custom Resources in the left-side navigation pane.

Click Create from YAML in the upper-right corner.

Sample Template: Select Custom.

Template: Paste the following code to the code editor.

View YAML content

apiVersion: alibabacloud.com/v1
kind: AlbConfig
metadata:
  name: alb-demo
spec:
  config:
    name: alb-test
    addressType: Internet
    zoneMappings:
    - vSwitchId: vsw-uf6ccg2a9g71hx8go****
    - vSwitchId: vsw-uf6nun9tql5t8nh15****
  listeners:
    - port: 80
      protocol: HTTP

The following table describes the parameters that you can configure.

Parameter	Required	Description
metadata.name	Yes	The name of the AlbConfig. Note The name of the AlbConfig must be unique in the cluster. When you create an AlbConfig, make sure that the AlbConfig name is unique to prevent conflicts.
spec.config.name	No	The name of the ALB instance.
spec.config.addressType	No	The network type of the ALB instance. Valid values: Internet (default): Internet-facing. The ALB instance provides services to the Internet and is accessible from the Internet. Note An ALB instance is associated with elastic IP addresses (EIPs) to provide Internet-facing services. If you use an Internet-facing ALB instance, you are charged instance fees and bandwidth or data transfer fees for the EIPs. For more information, see Pay-as-you-go. Intranet: internal-facing. An internal-facing ALB instance provides services within a VPC and cannot be accessed from the Internet.
spec.config.zoneMappings	Yes	The IDs of the vSwitches. For more information about how to create a vSwitch, see Create and manage a vSwitch. Note The specified vSwitch must be deployed in a zone supported by the ALB instance and deployed in the same VPC as the cluster. For more information about the regions and zones supported by ALB, see Regions and zones supported by ALB. ALB supports multi-zone deployment. If the current region supports two or more zones, select vSwitches in at least two zones to ensure high availability.
spec.listeners	No	The listener port and protocol of the ALB instance. In this example, an HTTP listener that uses port 80 is configured. A listener defines how ALB receives traffic. We recommend that you retain the listener configuration. Otherwise, you must create a listener before you can use ALB Ingresses.

After the configuration is complete, click Create. The Created message appears.
Check whether the ALB instance is created:
1. Log on to the ALB console.
2. In the top navigation bar, select the region in which the ALB instance is deployed.
3. On the Instances page, an ALB instance named alb-test is displayed in the instance list. This indicates that the ALB instance is created.

kubectl

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

View YAML content

apiVersion: alibabacloud.com/v1
kind: AlbConfig
metadata:
  name: alb-demo
spec:
  config:
    name: alb-test
    addressType: Internet
    zoneMappings:
    - vSwitchId: vsw-uf6ccg2a9g71hx8go****
    - vSwitchId: vsw-uf6nun9tql5t8nh15****
  listeners:
    - port: 80
      protocol: HTTP

The following table describes the parameters that you can configure.

Parameter	Required	Description
metadata.name	Yes	The name of the AlbConfig. Note The name of the AlbConfig must be unique in the cluster. When you create an AlbConfig, make sure that the AlbConfig name is unique to prevent conflicts.
spec.config.name	No	The name of the ALB instance.
spec.config.addressType	No	The network type of the ALB instance. Valid values: Internet (default): Internet-facing. The ALB instance provides services to the Internet and is accessible from the Internet. Note An ALB instance is associated with EIPs to provide Internet-facing services. If you use an Internet-facing ALB instance, you are charged instance fees and bandwidth or data transfer fees for the EIPs. For more information, see Pay-as-you-go. Intranet: internal-facing. An internal-facing ALB instance provides services within a VPC and cannot be accessed from the Internet.
spec.config.zoneMappings	Yes	The IDs of the vSwitches. For more information about how to create a vSwitch, see Create and manage a vSwitch. Note The specified vSwitch must be deployed in a zone supported by the ALB instance and deployed in the same VPC as the cluster. For more information about the regions and zones supported by ALB, see Regions and zones supported by ALB. ALB supports multi-zone deployment. If the current region supports two or more zones, select vSwitches in at least two zones to ensure high availability.
spec.listeners	No	The listening port and protocol of the ALB instance. In this example, an HTTP listener that uses port 80 is configured. A listener defines how ALB receives traffic. We recommend that you retain the listener configuration. Otherwise, you must create a listener before you can use ALB Ingresses.

Run the following command to create an AlbConfig object:

kubectl apply -f alb-test.yaml

Expected output:

albconfig.alibabacloud.com/alb-demo created

Step 3: Create an IngressClass

We recommend that you create an IngressClass for each AlbConfig.

ACK console

Log on to the ACK console. In the left-side navigation pane, click Clusters.
On the Clusters page, click the name of the cluster that you want to manage and choose Workloads > Custom Resources in the left-side navigation pane.

Click Create from YAML in the upper-right corner.

Sample Template: Select Custom.

Template: Paste the following code to the code editor.

View YAML 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

The following table describes the parameters that you can configure.

Parameter	Required	Description
metadata.name	Yes	The name of the IngressClass. Note The name of an IngressClass must be unique in the cluster. Therefore, when you create an IngressClass, make sure that the IngressClass name is unique to prevent conflicts.
spec.parameters.name	Yes	The name of the associated AlbConfig.

After the configuration is complete, click Create. The Created message appears.
Check whether the IngressClass is created:
1. In the left-side navigation pane, choose Workloads> Custom Resources.
2. Select the Resource Objects tab.
3. In the API Group search box, enter IngressClass. The IngressClass is displayed.

kubectl

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

View YAML 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

The following table describes the parameters that you can configure.

Parameter	Required	Description
metadata.name	Yes	The name of the IngressClass. Note The name of an IngressClass must be unique in the cluster. Therefore, when you create an IngressClass, make sure that the IngressClass name is unique to prevent conflicts.
spec.parameters.name	Yes	The name of the associated AlbConfig.

Run the following command to create an IngressClass:

  kubectl apply -f alb.yaml

Expected output:

ingressclass.networking.k8s.io/alb created

Step 4: Create an Ingress

ACK console

Log on to the ACK console. In the left-side navigation pane, click Clusters.
On the Clusters page, click the name of the cluster that you want to manage and choose Network > Ingresses in the left-side navigation pane.

Click Create from YAML in the upper-right corner.

Sample Template: Select Custom.

Template: Paste the following code to the code editor.

View YAML content

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

The following table describes the parameters that you can configure.

Parameter	Required	Description
metadata.name	Yes	The name of the Ingress. Note The name of an Ingress must be unique in the cluster. Therefore, when you create an Ingress, make sure that the Ingress name is unique to prevent conflicts.
spec.ingressClassName	Yes	The name of the associated IngressClass.
spec.rules.host	No	The domain name of the HTTP host header. You must set this parameter to a custom domain name. When you access the domain name, such as http://demo.domain.ingress.top, in a browser, the browser automatically adds the Host: demo.domain.ingress.top header when sending an HTTP request. This way, the server identifies the destination host based on the header. In Kubernetes, the host field in an Ingress rule is used to match the host header in a request. If the host header is matched, the request is routed to the corresponding backend Service. Note If you specify a custom domain name, make sure that the domain name has an Internet Content Provider (ICP) number. Otherwise, the domain name may fail to be resolved. For more information, see ICP filing application overview. If this parameter is not configured, the Ingress rule matches all requests that are sent to the Ingress controller.
spec.rules.http.paths.path	Yes	The URL path.
spec.rules.http.paths.pathType	Yes	The URL matching rule. For more information, see Forward requests based on URL paths.
spec.rules.http.paths.backend.service.name	Yes	The name of the Service that you created.
spec.rules.http.paths.backend.service.port.number	Yes	The port number of the Service that you created. Make sure that the port is valid because the port is used to route requests to the backend Service.

After the configuration is complete, click Create. The Created message appears.
Check that the Ingress is created:
1. In the left-side navigation pane, choose Network > Ingresses. The Ingress named cafe-ingress is displayed.
2. In the Endpoint column of cafe-ingress, you can view the endpoint.

kubectl

Create a file named cafe-ingress.yaml and paste the following content to the file. The file is used to create an Ingress.

View YAML content

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

The following table describes the parameters that you can configure.

Parameter	Required	Description
metadata.name	Yes	The name of the Ingress. Note The name of an Ingress must be unique in the cluster. Therefore, when you create an Ingress, make sure that the Ingress name is unique to prevent conflicts.
spec.ingressClassName	Yes	The name of the associated IngressClass.
spec.rules.host	No	The domain name of the HTTP host header. You must set this parameter to a custom domain name. When you access the domain name, such as http://demo.domain.ingress.top, in a browser, the browser automatically adds the Host: demo.domain.ingress.top header when sending an HTTP request. This way, the server identifies the destination host based on the header. In Kubernetes, the host field in an Ingress rule is used to match the host header in a request. If the host header is matched, the request to the corresponding backend Service. Note If you specify a custom domain name, make sure that the domain name has an ICP number. Otherwise, the domain name may fail to be resolved. For more information, see ICP filing application overview. If this parameter is not configured, the Ingress rule matches all requests that are sent to the Ingress controller.
spec.rules.http.paths.path	Yes	The URL path.
spec.rules.http.paths.pathType	Yes	The URL matching rule. For more information, see Forward requests based on URL paths.
spec.rules.http.paths.backend.service.name	Yes	The name of the Service that you created.
spec.rules.http.paths.backend.service.port.number	Yes	The port number of the Service that you created. Make sure that the port is valid because the port is used to route requests to the backend Service.

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.networking.k8s.io/cafe-ingress created
```

(Optional) Run the following command to obtain the domain name of the ALB instance:

kubectl get ingress

Expected output:

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

(Optional) Step 5: Configure domain name resolution

If you set the spec.rules.host parameter to a custom domain name when you create the Ingress, you must add a CNAME record to map the domain name to the domain name of the ALB instance. Then, you can access the Services through the custom domain name.

Log on to the ACK console.
Click the cluster name to go to the cluster details page.
In the left-side navigation pane, choose Network > Ingresses.
In the Endpoint column of cafe-ingress, copy the domain name.

To create a CNAME record, perform the following steps:

Log on to the Alibaba Cloud DNS console.
On the Domain Name Resolution page, click Add Domain Name.
In the Add Domain Name dialog box, enter the domain name of your host and click OK.
Important
Before you create the CNAME record, you must use a TXT record to verify the ownership of the domain name.
In the Actions column of the domain name that you want to manage, click DNS Settings.
On the DNS Settings page, click Add DNS Record.

In the Add DNS Record panel, configure the following parameters and click OK.

Parameter	Description
Record Type	Select CNAME from the drop-down list.
Hostname	Enter the prefix of the domain name, such as `www`.
DNS Request Source	Select Default.
Record Value	Enter the CNAME. The CNAME is the domain name that you copied.
TTL	Select a time-to-live (TTL) value for the CNAME record to be cached on the DNS server. In this example, the default value is used.

Step 6: Verify traffic forwarding

Enter "test domain name + URL path" in the address bar of a browser to check whether traffic is forwarded to the specified Service.

Note

If you configured a custom domain name, the test domain name is the custom domain name.
If you have not configured a custom domain name, the "test domain name" is the endpoint of cafe-ingress.

In this example, demo.domain.ingress.top is used.

Enter demo.domain.ingress.top/coffee in the address bar of a browser. The page for the coffee-svc Service appears.
Enter demo.domain.ingress.top/tea in the address bar of a browser. The page for the tea-svc Service appears.

References

For more information about advanced ALB Ingress configurations, such as forwarding requests destined for different domain names or URLs to different backend server groups, health checks, redirecting requests from HTTP to HTTPS, canary releases, and custom listener ports, see Advanced ALB Ingress configurations.
For more information about how to configure custom ALB Ingress routing rules, routing conditions, and actions, see Customize the routing rules of an ALB Ingress.
For more information about how to use HTTPS listeners to forward HTTPS requests, see Use an ALB Ingress to configure certificates for an HTTPS listener.
For more information about how to troubleshoot ALB Ingress issues, see ALB Ingress FAQ.