Container Service for Kubernetes:Schedule an application pod to a specific node pool

Procedure

1. Add a label to the nodes in a node pool.
   Container Service for Kubernetes (ACK) allows you to manage a group of cluster nodes by using a node pool. For example, you can centrally manage the labels and taints of the nodes in a node pool. For more information about how to create a node pool, see Manage node pools.
   1. Log on to the ACK console.
   2. In the left-side navigation pane of the ACK console, click Clusters.
   3. On the Clusters page, find the cluster that you want to manage and click Node Pools in the Actions column.
   4. In the upper-right corner of the Node Pools page, click Create Node Pool.
   5. In the Create Node Pool dialog box, click Show Advanced Options and click on the right side of Node Label to add labels to nodes.
      In this example, the pod: nginx label is added.
   You can also click Scale Out in the Actions column of a node pool to update or add labels. If auto scaling is enabled for a node pool, click Modify in the Actions column to update or add labels.
2. Configure a scheduling policy for an application pod.
   After the preceding step is completed, the pod: nginx label is added to the nodes in the node pool. You can set the nodeSelector or nodeAffinity field in pod configurations to ensure that an application pod is scheduled to nodes with matching labels in a node pool. Perform the following steps:
   • Set nodeSelector.
     nodeSelector is a field in the spec section of pod configurations. Add the pod: nginx label to nodeSelector. Example:

     apiVersion: apps/v1 
     kind: Deployment
     metadata:
       name: nginx-deployment-basic
       labels:
         app: nginx
     spec:
       replicas: 2
       selector:
         matchLabels:
           app: nginx
       template:
         metadata:
           labels:
             app: nginx
         spec:
           nodeSelector:
             pod: nginx      # After you add the label in this field, the application pod can run only on nodes with this label in the node pool. 
           containers:
           - name: nginx
             image: nginx:1.7.9
             ports:
             - containerPort: 80

   • Set nodeAffinity.
     You can also use nodeAffinity to schedule an application pod based on your requirements. nodeAffinity supports the following scheduling policies:

     • - requiredDuringSchedulingIgnoredDuringExecution

       If this policy is used, a pod can be scheduled only to a node that meets the match rules. If no node meets the match rules, the system retries until a node that meets the rules is found. IgnoreDuringExecution indicates that if the label of the node where the pod is deployed changes and no longer meets the match rules, the pod continues to run on the node.

     • - preferredDuringSchedulingIgnoredDuringExecution

       If this policy is used, the pod is preferably scheduled to a node that meets the match rules. If no node meets the rules, the system ignores the rules.

     In the following example, the requiredDuringSchedulingIgnoredDuringExecution policy is used to ensure that the application pod always runs on a node in a specific node pool.

     apiVersion: apps/v1
     kind: Deployment
     metadata:
       name: nginx-with-affinity
       labels:
         app: nginx-with-affinity
     spec:
       replicas: 2
       selector:
         matchLabels:
           app: nginx-with-affinity
       template:
         metadata:
           labels:
             app: nginx-with-affinity
         spec:
           affinity:
             nodeAffinity:
               requiredDuringSchedulingIgnoredDuringExecution:
                 nodeSelectorTerms:
                 - matchExpressions:
                   - key: pod
                     operator: In      # The application runs on a node that has the pod: nginx label. 
                     values:
                     - nginx
           containers:
           - name: nginx-with-affinity
             image: nginx:1.7.9
             ports:
             - containerPort: 80