:Use an automatically created SLB instance to expose an application

Precautions

• The CCM creates and configures SLB resources for only Services with the Type=LoadBalancer setting.

Important

If you change the setting for a Service from Type=LoadBalancer to Type!=LoadBalancer, the CCM deletes the configurations of the SLB instance created for the Service. As a result, the Service cannot be accessed by using the SLB instance.

• The CCM uses a declarative API and automatically updates the configurations of an SLB instance to match the configurations of the exposed Service when specific conditions are met. The SLB configurations that you modify in the SLB console may be overwritten by the CCM.

  Important

  Do not modify the configurations of an SLB instance that is created and maintained by Kubernetes in the SLB console. Otherwise, Kubernetes may overwrite your modifications and consequently the relevant LoadBalancer Service may become inaccessible.

• You cannot change the SLB instance that is associated with a LoadBalancer Service after the Service is created. To change the SLB instance, you must create a new Service.

Quotas

• The CCM creates SLB instances for Services with the Type=LoadBalancer setting. By default, you can have a maximum of 60 SLB instances within your Alibaba Cloud account. To create more SLB instances, apply for a quota increase in the log on to the Quota Center console and submit an application.

• The CCM automatically creates listeners that use Service ports for SLB instances. By default, each SLB instance supports at most 50 listeners. To increase the number of listeners supported by each SLB instance, apply for a quota increase in the log on to the Quota Center console and submit an application.

• For more information about the limits on SLB, see Limits.

  To query the SLB resource quotas, go to the Quota Center page in the SLB console.

Step 1: Deploy an application

The following section describes how to use the kubectl command-line tool to deploy an application.

1. Create a file named my-nginx.yaml file and add the following YAML content to the file:

   apiVersion: apps/v1 # for versions before 1.8.0 use apps/v1beta1
   kind: Deployment
   metadata:
     name: my-nginx    # The name of the sample application. 
     labels:
       app: nginx
   spec:
     replicas: 3       # The number of replicated pods. 
     selector:
       matchLabels:
         app: nginx     # You must specify the same value in the selector of the Service that is used to expose the application. 
     template:
       metadata:
         labels:
           app: nginx
       spec:
         containers:
         - name: nginx
           image: registry.cn-hangzhou.aliyuncs.com/acs-sample/nginx:latest     # Replace with the address of the image that you want to use in the format of <image_name:tags>. 
           ports:
           - containerPort: 80                                # The port that you want to expose in the Service.

2. Run the following command to deploy the my-nginx application:

   kubectl apply -f my-nginx.yaml

3. Run the following command to query the status of the application:

   kubectl get deployment my-nginx

   Expected output:

   NAME       READY   UP-TO-DATE   AVAILABLE   AGE
   my-nginx   3/3     3            3           50s

Step 2: Use an automatically created SLB instance to expose an application

You can create a LoadBalancer Service in the ACS console or by using kubectl. After the Service is created, you can use the Service to expose the application.