Container Service for Kubernetes:Best practices for associating deployment sets with node pools

Limits

Cluster feature usage guidelines

• Deployment sets are supported by ACK dedicated clusters and ACK managed clusters.

• You can associate a deployment set with a node pool only when you create the node pool. Existing node pools cannot have deployment sets enabled. You can associate only one deployment set with each node pool and you cannot change the deployment sets that are associated with node pools.

• You cannot manually add ECS instances to or remove ECS instances from deployment sets. If you want to change the number of ECS instances in a deployment set, you can scale the node pool with which the deployment set is associated. For more information, see Create a node pool.

• After you associate a deployment set with a node pool, the node pool does not support preemptible instances.

Deployment set quotas and specifications limits

• By default, node pool deployment sets are implemented based on a high-availability strategy. In a deployment set that adopts the high availability strategy, you can create up to 20 ECS instances per zone. You can use the following formula to calculate the maximum number of ECS instances that you can create in a deployment set within an Alibaba Cloud region: 20 × Number of zones within the region. For more information, see Deployment set.

  You cannot increase the number of ECS instances in a deployment set. However, if you want to increase the maximum number of deployment sets that your Alibaba Cloud account can have, request a quota increase in the Quota Center console. For more information about the limits and quotas of deployment sets, see Deployment set limits.

• Instance families that support different deployment strategies:

  Specific instance families support only specific deployment strategies. The following table describes the instance families that support different deployment strategies.

  Note

  You can also call the DescribeDeploymentSetSupportedInstanceTypeFamily operation to query instance families that support a specific deployment strategy.

  Deployment strategy	Instance families that support the deployment strategy
  High availability strategy or high availability group strategy	g8a, g8i, g8y, g7se, g7a, g7, g7h, g7t, g7ne, g7nex, g6, g6e, g6a, g5, g5ne, sn2ne, sn2, and sn1 c8a, c8i, c8y, c7se, c7, c7t, c7nex, c7a, c6, c6a, c6e, c5, ic5, and sn1ne r8a, r8i, r8y, r7, r7se, r7t, r7a, r6, r6e, r6a, re6, re6p, r5, re4, se1ne, and se1 hfc8i, hfg8i, hfr8i, hfc7, hfg7, hfr7, hfc6, hfg6, hfr6, hfc5, and hfg5 d3c, d2s, d2c, d1, d1ne, d1-c14d3, and d1-c8d3 i3g, i3, i2, i2g, i2ne, i2gne, and i1 ebmg5, ebmc7, ebmg7, ebmr7, sccgn6, scch5, scch5s, sccg5, and sccg5s e, t6, xn4, mn4, n4, e4, n2, and n1 gn6i
  Low latency strategy	g8a, g8i, g8ae, and g8y c8a, c8i, c8ae, and c8y r8a, r8i, r8ae, and r8y ebmc7, ebmg7, and ebmr7

• Insufficient instance resources within the region may result in a failure to create ECS instances or start pay-as-you-go instances that were stopped in economical mode in a deployment set. Wait for a while and then try to create or start the instances again.

Associate a deployment set with a node pool in the ACK console

1. Log on to the ACK console. In the left-side navigation pane, click Clusters.

2. On the Clusters page, find the cluster that you want to manage and click its name. In the left-side navigation pane, choose Nodes > Node Pools.

3. In the upper-right corner of the Node Pools page, click Create Node Pool. In the Create Node Pool dialog box, configure the parameters, select a deployment set, and then click Confirm Order.

   For more information about the parameters, see Procedure.

Use cases

Your applications are deployed in the same node pool and pod anti-affinity is configured for pods that belong to the same application. Each node can host only one pod.

This use case shows how to schedule three replicated pods in a Deployment to three different nodes.

1. Create a node pool that contains three nodes and specify the ID of the deployment set that you want to associate with the node pool. For more information, see Associate a deployment set with a node pool in the ACK console.

   After you create the node pool, click the name of the node pool on the Node Pools page. The Nodes tab shows the nodes that are contained in the node pool.

   Log on to the ECS console. In the left-side navigation pane, choose Deployment & Elasticity > Deployment Sets. The Deployment Sets page shows that the three nodes belong to the specified deployment set.

2. Create a YAML file based on the following content.

   Deploy three pods and configure anti-affinity to schedule the pods to three different nodes.

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: nginx
     labels:
       app: nginx
   spec:
     replicas: 3
     selector:
       matchLabels:
         app: nginx
     template:
       metadata:
         name: nginx
         labels:
           app: nginx
       spec:
         affinity:
           podAntiAffinity:
             requiredDuringSchedulingIgnoredDuringExecution:  # Configure the scheduling policy. 
             - labelSelector:
                 matchExpressions:
                 - key: app
                   operator: In
                   values:
                   - nginx
               topologyKey: kubernetes.io/hostname
         nodeSelector:
             alibabacloud.com/nodepool-id: <nodepool-id>  # Specify the ID of the node pool. 
         containers:
         - name: nginx
           image: nginx
           resources:
             limits:
               cpu: 1
             requests:
               cpu: 1

   Results

   On the Deployments page, click the Deployment that you want to manage. The Pods tab shows that the pods are scheduled to three different nodes.

Your applications are deployed in the same node pool. Pods that belong to the same application can be scheduled to different nodes across multiple zones.

1. Create a node pool that contains four nodes, specify the ID of the deployment set that you want to associate with the node pool, and select vSwitches that are deployed in multiple zones. For more information, see Associate a deployment set with a node pool in the ACK console.

After you create the node pool, four nodes and four zones are displayed on the Nodes page. ECS instances are deployed in four different zones and are added to the same deployment set based on the balanced distribution policy of Auto Scaling.

Log on to the ECS console. In the left-side navigation pane, choose Deployment & Elasticity > deployment set. The Deployment Sets page shows that the four nodes in the node pool belong to the specified deployment set.

2. Create a YAML file based on the following content.

3. You can use pod topology spread constraints to schedule pods that belong to the same application to different nodes across multiple zones. For more information, see Pod topology spread constraints.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  replicas: 4
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      name: nginx
      labels:
        app: nginx
    spec:
      topologySpreadConstraints:
        - maxSkew: 1
          topologyKey: kubernetes.io/hostname
          whenUnsatisfiable: DoNotSchedule
          labelSelector:
              matchLabels:
                app: nginx
        - maxSkew: 1
          topologyKey: topology.kubernetes.io/zone
          whenUnsatisfiable: DoNotSchedule
          labelSelector:
              matchLabels:
                app: nginx
      nodeSelector:
          alibabacloud.com/nodepool-id: <nodepool-id>  #Specify the ID of the node pool. 
      containers:
      - name: nginx
        image: nginx
        resources:
          limits:
            cpu: 1
          requests:
            cpu: 1

4. Results

On the Deployments page, click the Deployment that you want to manage. The Pods tab shows that pods belonging to the same application are scheduled to different nodes across multiple zones.

References

• You can also Use Terraform to associate a deployment set with a node pool.

• For more information about recommended configurations on high availability clusters architecture, see Suggested configurations for creating HA clusters.