Container Compute Service:Schedule pods based on inter-pod affinity

Usage notes

Inter-pod affinity contains the affinity and anti-affinity modes. Both modes have the same protocol format and consist of the requiredDuringSchedulingIgnoredDuringExecution rule and the preferredDuringSchedulingIgnoredDuringExecution rule. The TopologyKey field is required, which corresponds to the label of the virtual node. The following table describes the topology labels supported by ACS for different types of nodes.

ACS supports various compute classes. The following constraints exist when you configure other fields of inter-pod affinity for pods of different compute classes.

• requiredDuringSchedulingIgnoredDuringExecution

  Compute class	Field	Description	Constraint
  General-purpose Performance-enhanced	LabelSelector	This field is used to find matching pods. Pods that match this label selector are counted to determine the number of pods in the topology domain.	GPU-accelerated pods and GPU-HPN pods are not counted.
  	Namespaces	This field is used to find matching namespaces and can be used together with the LabelSelector field.
  	NamespaceSelector	This field is similar to the Namespaces field, except it retrieves namespaces based on the namespace label.
  GPU-accelerated GPU-HPN	LabelSelector	This field is used to find matching pods. Pods that match this label selector are counted to determine the number of pods in the topology domain.	General-purpose and performance-enhanced pods are not counted.
  	Namespaces	This field is used to find matching namespaces and can be used together with the LabelSelector field.	Not supported
  	NamespaceSelector	This field is similar to the Namespaces field, except it retrieves namespaces based on the namespace label.	Not supported

• preferredDuringSchedulingIgnoredDuringExecution

  Compute class	Field	Description	Constraint
  General-purpose Performance-enhanced	LabelSelector Namespaces NamespaceSelector	None	GPU-accelerated pods and GPU-HPN pods are not counted.
  GPU-accelerated GPU-HPN	All fields	None	Not supported

For more information about the fields, see Inter-pod affinity and anti-affinity.

Examples

The following example shows how to schedule pods to a specific zone by configuring the podAffinity field.

1. Run the following command to view the nodes in the cluster:

   kubectl get node

   Expected output:

   NAME                            STATUS   ROLES   AGE     VERSION
   virtual-kubelet-cn-hangzhou-i   Ready    agent   5h42m   v1.28.3-xx
   virtual-kubelet-cn-hangzhou-j   Ready    agent   5h42m   v1.28.3-xx

2. Create a file named with-affinity-pod.yaml and add the following content to the file:

   apiVersion: v1
   kind: Pod
   metadata:
     labels:
       pod-affinity-label: with-pod-affinity
     name: with-affinity-label-pod
   spec:
     containers:
       - args:
           - 'infinity'
         command:
           - sleep
         image: registry-cn-hangzhou.ack.aliyuncs.com/acs/stress:v1.0.4
         imagePullPolicy: IfNotPresent
         name: stress
         resources:
           limits:
             cpu: '1'
             memory: 1Gi
           requests:
             cpu: '1'
             memory: 1Gi

3. Run the following command to deploy the with-affinity-label-pod file to the cluster:

   kubectl apply -f with-affinity-pod.yaml

4. Run the following command to view the distribution results of pods:

   kubectl get pod -o wide

   Expected output:

   NAME                      READY   STATUS    RESTARTS   AGE   IP              NODE                            NOMINATED NODE   READINESS GATES
   with-affinity-label-pod   1/1     Running   0          75s   192.168.xx.xxx  virtual-kubelet-cn-hangzhou-i   <none>           <none>

   The output indicates that the pods are scheduled to the cn-hangzhou-i zone.

5. Create a file named origin-affinity-pod.yaml and add the following content to the file:

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: dep-pod-affinity
     labels:
       app: pod-affinity-demo
   spec:
     replicas: 4
     selector:
       matchLabels:
         app: pod-affinity-demo
     template:
       metadata:
         labels:
           app: pod-affinity-demo
       spec:
         containers:
         - name: pod-affinity-demo
           image: registry-cn-hangzhou.ack.aliyuncs.com/acs/stress:v1.0.4
           command:
           - "sleep"
           - "infinity"
           resources:
             limits:
               cpu: '1'
               memory: 1Gi
             requests:
               cpu: '1'
               memory: 1Gi
         # Specify the affinity between pods. This pod must be deployed in the same zone as the pod with the <pod-affinity-label:with-pod-affinity> label.
         affinity:
           podAffinity:
             requiredDuringSchedulingIgnoredDuringExecution:
             - labelSelector:
                 matchExpressions:
                 - key: pod-affinity-label
                   operator: In
                   values:
                   - with-pod-affinity
               topologyKey: topology.kubernetes.io/zone

6. Run the following command to deploy the origin-affinity-pod.yaml file to the cluster:

   kubectl apply -f origin-affinity-pod.yaml

7. Run the following command to view the distribution results of pods:

   kubectl get pod -o wide

   Expected results:

   NAME                                READY   STATUS    RESTARTS   AGE     IP              NODE                            NOMINATED NODE   READINESS GATES
   dep-pod-affinity-6b9d4f7c87-5jlfx   1/1     Running   0          3m26s   192.168.xx.xxx  virtual-kubelet-cn-hangzhou-i   <none>           <none>
   dep-pod-affinity-6b9d4f7c87-hwdpc   1/1     Running   0          3m26s   192.168.xx.xxx  virtual-kubelet-cn-hangzhou-i   <none>           <none>
   dep-pod-affinity-6b9d4f7c87-jfcrq   1/1     Running   0          3m26s   192.168.xx.xxx  virtual-kubelet-cn-hangzhou-i   <none>           <none>
   dep-pod-affinity-6b9d4f7c87-xwbfr   1/1     Running   0          3m26s   192.168.xx.xxx  virtual-kubelet-cn-hangzhou-i   <none>           <none>
   with-affinity-label-pod             1/1     Running   0          6m30s   192.168.xx.xxx  virtual-kubelet-cn-hangzhou-i   <none>           <none>

   The output indicates that all pods are deployed in the same zone.