Container Service for Kubernetes:Enable node autoscaling

Before you begin

To use the node autoscaling feature effectively, we recommend that you first read Node scaling and understand the following:

How node autoscaling works and its features

Use cases suitable for node autoscaling

Important considerations before using node autoscaling

During a scale-in, subscription instances are removed from the cluster but not terminated. To avoid extra costs, use pay-as-you-go instances when you enable this feature.

Precautions

• Before you begin, make sure that you have activated the Auto Scaling service.

• For information about quotas and limits, see the Precautions for node scaling.

• Node autoscaling has known limitations with certain scheduling policies, which might lead to unexpected scaling behavior. If your workloads or components use an unsupported scheduling policy, we recommend one of the following solutions:

  • Solution 1: Switch to node instant scaling.

  • Solution 2: Deploy the affected workloads or components to a node pool where node scaling is not enabled.

    For example, to deploy the ack-node-local-dns-admission-controller component, deploy it to a node pool where node scaling is not enabled and add the following node affinity requirement to the component's configuration.

    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: "k8s.aliyun.com"
            operator: "NotIn"
            values: ["true"]

• The cluster-autoscaler component requires node resources during updates or deployments. Insufficient resources can cause these operations to fail and disrupt scaling. Ensure your nodes have adequate resources to prevent such failures.

This feature involves the following steps:

1. Step 1: Enable node autoscaling for the cluster: You must first enable node autoscaling at the cluster level for node pool auto scaling policies to take effect.

2. Step 2: Configure autoscaled node pools: The node autoscaling feature affects only node pools where it is enabled. Therefore, you must set the scaling mode of specific node pools to Auto.

Step 1: Enable node autoscaling

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

2. On the Clusters page, click the name of your cluster. In the left navigation pane, click Nodes > Node Pools.

3. On the Node Pools page, next to Node Scaling, click Enable.

4. If this is your first time using node autoscaling, follow the on-screen instructions to activate the Auto Scaling service and grant the required permissions. If you have already done this, skip this step.

   • ACK managed cluster: Authorize the AliyunCSManagedAutoScalerRole role.

   • ACK dedicated cluster: Authorize the KubernetesWorkerRole role and attach the AliyunCSManagedAutoScalerRolePolicy.

     In the Node Scaling Configuration dialog box, after the precheck passes, click the RAM role link (such as KubernetesWorkerRole-xxxx) to complete authorization in the RAM console.

5. On the Node Scaling Configuration page, set Node Scaling Plan to Auto Scaling, configure the parameters, and then click OK.

   You can switch the scaling solution after it is selected. To switch, change the selection to node instant scaling, read the on-screen prompts carefully, and follow the instructions to complete the operation.

   Parameter	Description
   Node Pool Scale-out Policy	Random Policy: If multiple node pools are eligible for scale-out, one is chosen at random. Default Policy: If multiple node pools are eligible for scale-out, it chooses the one that results in the least resource waste. Priority-based Policy: If multiple node pools are eligible for scale-out, it chooses the one with the highest priority. Node pool priority is defined by the Node Pool Scale-out Priority parameter.
   Node Pool Scale-out Priority	Sets the scale-out priority for node pools. This parameter takes effect only when Node Pool Scale-out Policy is set to Priority-based Policy. Value range: an integer from 1 to 100. A larger value indicates a higher priority. You must click Add next to the parameter, select an autoscaled node pool, and set a priority for it. If no autoscaled node pools are available, you can ignore this parameter for now and set the priority after you complete Step 2: Configure autoscaled node pools.
   Scaling Sensitivity	The interval at which the system checks whether to perform scaling. The default value is 60s.
   During auto scaling, the scaling component automatically triggers scale-out events based on scheduling status. Important ECS nodes: The scaling component can scale in a node only when the conditions for Scale-in Threshold, Scale-in Trigger Delay, and Cooldown Period are all met. GPU nodes: The scaling component can scale in a GPU node only when the conditions for GPU Scale-in Threshold, Scale-in Trigger Delay, and Cooldown Period are all met.
   Allow Scale-in	Specifies whether to allow node scale-in. If this is turned off, scale-in-related configurations do not take effect. Use this setting with caution.
   Scale-in Threshold	The ratio of resource requests to the total resource capacity of a node in a node pool with node autoscaling enabled. A node is eligible for scale-in only if its CPU and memory resource utilization are both below the Scale-in Threshold.
   GPU Scale-in Threshold	The scale-in threshold for GPU instances. A GPU instance is eligible for scale-in only when its CPU, memory, and GPU utilization all fall below the configured GPU Scale-in Threshold.
   Scale-in Trigger Delay	The delay between when a node becomes eligible for scale-in and when the scale-in operation is performed. Unit: minutes. Default value: 10 minutes. Important The scaling component can perform a node scale-in only after the Scale-in Threshold condition is met and the Scale-in Trigger Delay duration has passed.
   Cooldown Period	The period after the most recent scale-out event during which the scaling component will not perform a scale-in. During the cooldown period, scale-in actions are paused, but the system continues to evaluate nodes for eligibility. Once the cooldown ends, any node that has met the scale-in conditions (threshold and deferral time) is scaled in. For example, with a 10-minute cooldown and a 5-minute deferral, no nodes are removed for 10 minutes after a scale-out. If a node becomes eligible at minute 2, it will be removed at minute 10, as it has been eligible for 8 minutes, which exceeds the 5-minute deferral.

   Advanced parameters

   Parameter	Description
   Pod Termination Timeout	Maximum wait time for pod termination during scale-in. Unit: seconds. If a pod is not evicted before the timeout, the node is not released.
   Minimum Pod Replicas	Scale-in protection threshold. Nodes with ReplicationController or ReplicaSet pods are not scaled in if the replica count falls below this value. Applies only to ReplicationController and ReplicaSet pods, not StatefulSet or DaemonSet.
   Enable DaemonSet Pod Eviction	When enabled, DaemonSet pods are evicted when their node is scaled in.
   Skip nodes with pods in the kube-system namespace	When enabled, nodes with kube-system namespace pods are excluded from scale-in. Note This does not apply to DaemonSet pods or mirror pods.

Step 2: Configure autoscaled node pools

You can either configure an existing node pool by changing its Scaling Mode to Auto, or create a new node pool with auto scaling enabled.

For detailed instructions, see Create and manage a node pool. The key parameters are described below:

Step 3: (Optional) Verify the result

After you complete these steps, the node autoscaling feature is ready to use. The node pool will indicate that auto scaling is active, and the system will automatically install the cluster-autoscaler component.

FAQ