Container Service for Kubernetes:Modify a node pool

Prerequisites

• An ACK cluster is created. For more information, see Create an ACK managed cluster.

• A kubectl client can be connected to the ACK cluster as expected. For more information, see Obtain the kubeconfig file of a cluster and use kubectl to connect to the cluster.

• A node pool is created in the cluster. For more information, see Create a node pool.

Precautions

• In most cases, after you modify a node pool, the modified configurations apply only to newly added nodes. Only in specific cases such as changing the labels and taints of existing nodes, the modified configurations also apply to the existing nodes in the node pool. If you perform O&M operations on a node pool, such as node pool upgrades, node repairing, Common Vulnerabilities and Exposures (CVE) vulnerability patching, and kubelet configuration customization, the configurations of the existing nodes in the node pool are also modified.

• Modifications to a node pool do not affect existing nodes or applications in the node pool.

Procedure

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

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

3. On the Node Pools page, find the node pool that you want to modify and click Edit in the Actions column.

4. In the dialog box that appears, modify the parameters of the node pool.

   Note

   In the following table, indicates that the parameter cannot be modified. indicates that the parameter can be modified.

   Parameter	Modifiable	Description
   Region		The region where the cluster resides.
   Container Runtime		For more information about container runtimes, see Comparison of Docker, containerd, and Sandboxed-Container.
   VPC		The virtual private cloud (VPC) in which the cluster resides is automatically selected.
   vSwitch		You can select up to three vSwitches that are deployed in different zones. If no vSwitch is available, click Create vSwitch. For more information, see Create and manage vSwitches. When the node pool is scaled out, nodes in the zones in which the selected vSwitches reside are added to the node pool. Node pools are scaled based on the scaling policy that you select in the advanced settings of the node pool.
   Auto Scaling		Specify whether to enable auto scaling. This feature provides cost-effective computing resource scaling based on business requirements and scaling policies. For more information, see Auto scaling overview. Before you enable this feature, you need to enable node auto scaling for the node pool. For more information, see Step 1: Enable node auto scaling.
   Billing Method		The following billing methods are supported for nodes in a node pool: pay-as-you-go, subscription, and preemptible instances. To ensure that all nodes in a node pool use the same billing method, ACK does not allow you to change the billing method of a node pool from pay-as-you-go or subscription to preemptible instances. For example, you cannot change the billing method of a node pool from pay-as-you-go or subscription to preemptible instances. If you select the pay-as-you-go billing method, you are charged for the Elastic Compute Service (ECS) instances in the node pool on a pay-as-you-go basis. You are not charged for using the node pool. If you select the subscription billing method, you must configure the Duration and Auto Renewal parameters. If you select the preemptible instances billing method, you must configure the following parameter at the same time. Upper Price Limit of Current Instance Spec: If the real-time market price of an instance type that you select is lower than the value of this parameter, a preemptible instance of this instance type is created. After the protection period (1 hour) elapses, the system checks the spot price and resource availability of the instance type every 5 minutes. If the real-time market price exceeds your bid price or if the resource inventory is insufficient, the preemptible instance is released. Note If you change the billing method of a node pool, the change takes effect only on newly added nodes. The existing nodes in the node pool still use the original billing method. For more information about how to change the billing method of existing nodes in a node pool, see Change the billing method of an instance from pay-as-you-go to subscription. ACK supports only preemptible instances with a protection period. For more information, see Best practices for preemptible instance-based node pools.
   Instance Type		You can select multiple instance types. You can filter instance types by vCPU, memory, architecture, or category. Note The instance types that you select are displayed in the Selected Types section. When the node pool is scaled out, ECS instances of the instance types that you select for the Instance Type parameter are created. The scaling policy of the node pool determines which instance types are used to create new nodes during scale-out activities. Select multiple instance types to improve the success rate of node pool scale-out operations. If the node pool fails to be scaled out because the instance types are unavailable or the instances are insufficient, you can specify more instance types for the node pool. The ACK console automatically evaluates the scalability of the node pool. You can view the scalability level when you create the node pool or after you create the node pool. For more information about ECS instance types, see Overview of instance families. For more information about node pool scalability, see Check the scalability of a node pool. Note Modifications to the instance types used by a node pool apply only to newly added nodes and do not take effect on existing nodes in the node pool. If you want to change the instance type of the existing nodes in a node pool, perform the following steps: If you want to upgrade the ECS instances, go to the ECS console and perform the operation. For more information, see Overview of instance configuration changes. To change the instance type of existing nodes, you must first remove the nodes from the cluster. Change the instance type for the node pool and then re-add the nodes to the node pool. For more information about how to remove a node from a cluster, see Remove nodes. ARM-based ECS instances support only images for ARM. For more information about ARM-based node pools, see Configure an ARM-based node pool.
   Selected Types		The selected instance types are displayed. If you select only GPU-accelerated instances, you can select Enable GPU Sharing on demand. For more information, see GPU sharing overview.
   System Disk		ESSD AutoPL, Enhanced SSD (ESSD), Standard SSD, and Ultra Disk are supported. The types of system disks that you can select depend on the instance types that you select. Disk types that are not displayed in the drop-down list are not supported by the instance types that you select. For more information about the disk types supported by different instance types, see Instance families. Note If you select Enhanced SSD (ESSD) as the system disk type, you can set a custom performance level for the system disk. You can select higher PLs for ESSDs with larger storage capacities. For example, you can select PL 2 for an ESSD with a storage capacity of more than 460 GiB. You can select PL 3 for an ESSD with a storage capacity of more than 1,260 GiB. For more information, see Capacities and performance levels. You can select Encryption only if you set the system disk type to Enhanced SSD (ESSD). By default, the default service CMK is used to encrypt the system disk. You can also use an existing CMK generated by using BYOK in KMS. You can select More System Disk Types and select a disk type other than the current one in the System Disk section to improve the success rate of system disk creation. The system will attempt to create a system disk based on the specified disk types in sequence.
   Mount Data Disk		ESSD AutoPL, Enhanced SSD (ESSD), SSD, and Ultra Disk are supported. The disk types that you can select depend on the instance types that you select. Disk types that are not displayed in the drop-down list are not supported by the instance types that you select. For more information about the disk types supported by different instance types, see Instance families. Note If you select Enhanced SSD (ESSD) as the system disk type, you can set a custom performance level for the system disk. You can select higher PLs for ESSDs with larger storage capacities. For example, you can select PL 2 for an ESSD with a storage capacity of more than 460 GiB. You can select PL 3 for an ESSD with a storage capacity of more than 1,260 GiB. For more information, see Capacities and performance levels. You can select Encryption for all disk types when you specify the type of data disk. By default, the default service CMK is used to encrypt the data disk. You can also use an existing CMK generated by using BYOK in KMS. The maximum number of data disks that can be mounted depends on the instance types that you select. You can view the selected data disks and the remaining number of data disks that you can mount on the right side of Mount Data Disk.
   Operating System		ACK supports images for the following operating systems: Alibaba Cloud Linux 3 Alibaba Cloud Linux 3 for ARM. ContainerOS Alibaba Cloud Linux 2 Alibaba Cloud Linux UEFI 2 Windows Windows Core CentOS For more information, see Overview of OS images. Note After you change the OS image of the node pool, the change takes effect only on newly added node. The existing nodes in the node pool still use the original OS image. For more information about how to update the OS images of existing nodes, see Node pool updates. To ensure that all nodes in the node pool use the same OS image, ACK allows you to only update the node OS image to the latest version. ACK does not allow you to change the type of OS image.
   Logon Type		Valid values: Key Pair, Password, and Later. Note If you select Reinforcement based on classified protection for the Security Reinforcement parameter, only the Password option is supported. Configure the logon type when you create the node pool: Key Pair: Alibaba Cloud SSH key pairs provide a secure and convenient method to log on to ECS instances. An SSH key pair consists of a public key and a private key. SSH key pairs support only Linux instances. For more information, see Overview. Password: The password must be 8 to 30 characters in length, and must contain uppercase letters, lowercase letters, digits, and special characters. Configure the logon type after you create the node pool: For more information, see Bind an SSH key pair to an instance and Reset the logon password of an instance.
   Username		If you select Key Pair or Password for Logon Type, you must select root or ecs-user as the username.
   Public IP		Specify whether to allocate an IPv4 address to each node. If you clear the check box, no public IP address is allocated. If you select the check box, you must also set the Bandwidth Billing Method and Peak Bandwidth parameters. Note This parameter takes effect only on newly added nodes and does not take effect on existing nodes. If you want to enable an existing node to access the Internet, you must create an elastic IP address (EIP) and associate the EIP with the node. For more information, see Associate an EIP with an ECS instance.
   CloudMonitor Agent		Specify whether to install the CloudMonitor agent. After you install the CloudMonitor agent on ECS nodes, you can view the monitoring information about the nodes in the CloudMonitor console. Note This parameter takes effect only on newly added nodes and does not take effect on existing nodes. If you want to install the CloudMonitor agent on an existing ECS node, go to the CloudMonitor console.

5. Click Show Advanced Options to configure advanced settings.

   Show advanced settings

   Parameter	Modifiable	Description
   ECS Tags		Add tags to the ECS instances that are automatically added during auto scaling. Tag keys must be unique. A key cannot exceed 128 characters in length. Keys and values cannot start with aliyun or acs:. Keys and values cannot contain https:// or http://. An ECS instance can have up to 20 tags. To increase the quota limit, submit an application in the Quota Center console. The following tags are automatically added to an ECS node by ACK and Auto Scaling. Therefore, you can add 17 tags to an ECS node. The following two ECS tags are added by ACK: ack.aliyun.com:<Cluster ID> ack.alibabacloud.com/nodepool-id:<Node pool ID> The following ECS tag is added by Auto Scaling: acs:autoscaling:scalingGroupId:<Scaling group ID>. Note After you enable auto scaling, the following ECS tags are added to the node pool by default: k8s.io/cluster-autoscaler:true and k8s.aliyun.com:true. The auto scaling component simulates scale-out activities based on node labels and taints. For this purpose, the format of node labels is changed to k8s.io/cluster-autoscaler/node-template/label/Label key:Label value and the format of taints is changed to k8s.io/cluster-autoscaler/node-template/taint/Taint key/Taint value:Taint effect. Modifications to the ECS labels apply only to newly added nodes and do not take effect on existing nodes in the node pool. If you want to modify the labels of existing nodes in the node pool, go to the ECS console and modify the labels of the ECS instances.
   Taints		Add taints to nodes. A taint consists of a key, a value, and an effect. A taint key can be prefixed. If you want to specify a prefixed taint key, add a forward slash (/) between the prefix and the remaining content of the key. For more information, see Taints and tolerations. The following limits apply to taints: Key: A key must be 1 to 63 characters in length, and can contain letters, digits, hyphens (-), underscores (_), and periods (.). A key must start and end with a letter or digit. If you want to specify a prefixed key, the prefix must be a subdomain name. A subdomain name consists of DNS labels that are separated by periods (.), and cannot exceed 253 characters in length. It must end with a forward slash (/). For more information about subdomain names, see DNS subdomain names. Value: A value cannot exceed 63 characters in length, and can contain letters, digits, hyphens (-), underscores (_), and periods (.). A value must start and end with a letter or digit. You can also leave a value empty. You can specify the following effects for a taint: NoSchedule, NoExecute, and PreferNoSchedule. NoSchedule: If a node has a taint whose effect is NoSchedule, the system does not schedule pods to the node. NoExecute: Pods that do not tolerate this taint are evicted after this taint is added to a node. Pods that tolerate this taint are not evicted after this taint is added to a node. PreferNoSchedule: The system attempts to avoid scheduling pods to nodes with taints that are not tolerated by the pods. Note Modifications to the taints apply only to newly added nodes and do not take effect on existing nodes in the node pool. If you want to modify the taints of existing nodes in the node pool, select Add Labels and Taints to Existing Nodes in the Node Label parameter. You can also click Manage Labels and Taints in the upper-right corner of the Nodes page to manually modify the taints.
   Node Label		Add labels to nodes. A label is a key-value pair. A label key can be prefixed. If you want to specify a prefixed label key, add a forward slash (/) between the prefix and the remaining content of the key. The following limits apply to labels: The key of a label must be 1 to 63 characters in length, and can contain letters, digits, hyphens (-), underscores (_), and periods (.). It must start and end with a letter or a digit. If you want to specify a prefixed key, the prefix must be a subdomain name. A subdomain name consists of DNS labels that are separated by periods (.), and cannot exceed 253 characters in length. It must end with a forward slash (/). For more information about subdomain names, see Subdomain names. The following prefixes are used by key Kubernetes components and cannot be used in node labels: kubernetes.io/ k8s.io/ Prefixes that end with kubernetes.io/ or k8s.io/. Example: test.kubernetes.io/. However, you can still use the following prefixes: kubelet.kubernetes.io/ node.kubernetes.io Prefixes that end with kubelet.kubernetes.io/. Prefixes that end with node.kubernetes.io. The value of a label cannot exceed 63 characters in length, and can contain letters, digits, hyphens (-), underscores (_), and periods (.). The value of a label can be empty or start and end with a letter or a digit. If you select Set New Nodes to Unschedulable, nodes are unschedulable when they are added to the cluster. You can set an existing node to schedulable on the Nodes page in the ACK console. Show details of the Add Labels and Taints to Existing Nodes parameter If you select this checkbox, modifications to labels and taints apply to both existing nodes and newly added nodes. If this checkbox is selected, the system synchronized the label or taint change of the node pool to the existing nodes in an incremental way instead of overwriting the labels of taints of the existing nodes. Assume that Node A has the following labels: testA : testA testB : testB The node pool uses the following label setting: testA : testA. After you change the label setting of the node pool to testC : testC, testA : testA is removed from the nodes in the node pool and testC : testC is added to the nodes. Consequently, Node A has the following labels after you submit the change: testB : testB testC : testC Show details of the Set to Unschedulable parameter If you select this checkbox, newly added nodes are unschedulable when they are added to the cluster. You can set an existing node to schedulable on the Nodes page in the ACK console. Note This parameter applies only to newly added nodes and does not take effect on existing nodes in the node pool.
   Scaling Policy		Priority: The system scales the node pool based on the priorities of the vSwitches that you select for the node pool. The vSwitches that you select are displayed in descending order of priority. If Auto Scaling fails to create ECS instances in the zone of the vSwitch with the highest priority, Auto Scaling attempts to create ECS instances in the zone of the vSwitch with a lower priority. Cost Optimization: The system creates instances based on the vCPU unit prices in ascending order. Preemptible instances are preferentially created when multiple preemptible instance types are specified in the scaling configurations. If preemptible instances cannot be created due to reasons such as insufficient stocks, the system attempts to create pay-as-you-go instances. If you set the Billing Method parameter to Preemptible Instance, you must configure the following parameters: Percentage of Pay-as-you-go Instances: Specify the percentage of pay-as-you-go instances in the node pool. Valid values: 0 to 100. Enable Supplemental Preemptible Instances: After you enable this feature, Auto Scaling automatically creates the same number of preemptible instances 5 minutes before the system reclaims the existing preemptible instances. The system sends a notification to Auto Scaling 5 minutes before it reclaims preemptible instances. Enable Supplemental Pay-as-you-go Instances: After you enable this feature, Auto Scaling attempts to create pay-as-you-go ECS instances to meet the scaling requirement if Auto Scaling fails to create preemptible instances for reasons such as that the unit price is too high or preemptible instances are insufficient. Distribution Balancing: The even distribution policy takes effect only if you select multiple vSwitches. This policy ensures that ECS instances are evenly distributed among the zones (the vSwitches) of the scaling group. If ECS instances are unevenly distributed across the zones due to reasons such as insufficient stocks, you can perform a rebalancing operation.
   Custom Image		After you specify Custom Image, the custom image will replace the default system image. Custom Images: All nodes in the cluster are deployed based on the custom image. For more information about how to create a custom image, see Create a Kubernetes cluster by using a custom image. Shared Images: All nodes in the cluster are deployed based on the shared image. For more information about shared images, see Procedure. Note You can use only custom images created based on Alibaba Cloud Linux, RHEL 8.x, and CentOS 7.x. To use this feature, submit an application in the Quota Center console.
   RDS Whitelist		Click Select RDS Instance to add node IP addresses to the whitelist of an ApsaraDB RDS instance.
   Custom Node Name		Specify whether to use a custom node name. If you choose to use a custom node name, the name of the node, name of the ECS instance, and hostname of the ECS instance are changed. Note If a Windows instance uses a custom node name, the hostname of the instance is fixed to an IP address. You need to use hyphens (-) to replace the periods (.) in the IP address. In addition, no prefix or suffix is allowed in the IP address. A custom node name consists of a prefix, an IP substring, and a suffix. A custom node name must be 2 to 64 characters in length. The name must start and end with a lowercase letter or digit. The prefix and suffix can contain letters, digits, hyphens (-), and periods (.). The prefix and suffix must start with a letter and cannot end with a hyphen (-) or period (.). The prefix and suffix cannot contain consecutive hyphens (-) or periods (.). The prefix is required due to ECS limits and the suffix is optional. For example, the node IP address is 192.XX.YY.55, the prefix is aliyun.com, and the suffix is test. If the node is a Linux node, the node name, ECS instance name, and ECS instance hostname are aliyun.com192.XX.YY.55test. If the node is a Windows node, the ECS instance hostname is 192-XX-YY-55 and the node name and ECS instance name are aliyun.com192.XX.YY.55test.
   Pre-defined Custom Data		To use this feature, submit an application in the Quota Center console. Nodes automatically run predefined scripts before they are added to the cluster. For more information about user-data scripts, see User-data scripts. For example, if you enter echo "hello world", a node runs the following script: #!/bin/bash echo "hello world" [Node initialization script]
   User Data		Nodes automatically run user-data scripts after they are added to the cluster. For more information about user-data scripts, see User-data scripts. For example, if you enter echo "hello world", a node runs the following script: #!/bin/bash [Node initialization script] echo "hello world" Note After you create a cluster or add nodes, the execution of the user-data script on a node may fail. We recommend that you log on to a node and run the grep cloud-init/var/log/messages command to view the execution log and check whether the execution succeeds or fails on the node.
   Private Pool Type		Note This parameter is in canary release. Valid values: Open, Do Not Use, and Specified. Open: The system automatically matches an open private pool. If no matching is found, resources in the public pool are used. Do Not Use: No private pool is used. Only resources in the public pool are used. Specified: Specify a private pool by ID. If the specified private pool is unavailable, ECS instances fail to start up. For more information, see Private pools.

6. Click Confirm. On the Node Pools page, check the state of the node pool. If Updating is displayed in the Status column, the node pool is being modified. After the node pool is modified, Active is displayed in the Status column.

References

• Scale a node pool

• Add existing ECS instances to an ACK cluster

• Remove a node

• Node pool O&M

• Best practices for nodes and node pools