Overview

Note：

Node pool feature is fully launched. You can continue to use the existing scaling groups in the cluster. However, TKE will stop upgrading of the legacy scaling group feature. Please convert the existing scaling groups to node pools as soon as possible (referring to user guide of node pool).
For any operations except the management of the existing scaling groups, please use the Node Pool feature.

To help you efficiently manage nodes in a Kubernetes cluster, TKE introduced the concept of node pool. Basic node pool features allow you to conveniently and quickly create, manage, and terminate nodes and dynamically scale nodes in or out.

• When a Pod in the cluster cannot be scheduled due to insufficient resources, scale-out will be triggered automatically, reducing labor costs.
• When the scale-in conditions are met, for example, when a node is idle, scale-in will be triggered automatically, reducing resource costs.

The following figure shows the overall architecture of a node pool.

Generally, all nodes in a node pool share the following attributes:

• Node-level operating system
• Billing type (currently pay-as-you-go and spot instances are supported)
• CPU/memory/GPU
• Launch parameters of Kubernetes components for nodes
• Custom launch script for nodes
• Kubernetes Label and Taints settings for nodes

In addition, TKE extends the following features for a node pool:

• Support managing node pool with CRD
• Maximum number of Pods for each node in a specific node pool
• Node-pool-level automatic repair and upgrade

Use Cases

When you need to use a large-scale cluster, we recommend that you use a node pool to manage nodes to improve the usability of the large-scale cluster. The following table describes multiple use cases for managing large-scale clusters and shows the effect of node pools in each use case.

Key Concepts

TKE Auto Scaling is implemented based on Tencent Cloud AS and the cluster-autoscaler of the Kubernetes community. The key concepts are described as follows:

• CA: cluster-autoscaler, an open-source component of the community.
• AS: autoscaler, the Tencent Cloud AS service
• ASG: as group, a specific scaling group
• ASA: as activity, a scaling activity
• ASC: as config, the AS launch configuration

Node Types in a Node Pool

To meet the requirements of different scenarios, the nodes in a node pool can be classified into the following two types:

Principles of Node Pool Auto Scaling

Node-pool-level auto scaling has two levels of scaling policies: the cluster autoscaler (CA) feature provided by Kubernetes, and the Auto Scaling (AS) capability provided by the Tencent Cloud AS service.

Note：

• When multiple node pools exist, the CA will select a suitable node pool to perform scaling for you and determine the specific number of nodes for scaling.
• The CA will trigger AS, and AS is responsible for performing node pool scaling.

• Node pool auto scale-out
  The CA will watch the pod and node resources in the cluster. When a pod in the cluster enters the pending state, the API of the cloud-provider, namely AS (scaling group), will be called to trigger scale-out. This adjusts the scaling groups to an expected quantity.
• Node pool auto scale-in
  When the calculated value of node utilization in the cluster is smaller than the user-specified threshold, the scale-in API of the cloud-provider, namely AS, will be called to perform scale-in on the specified nodes.

Features and Notes

References

You can log in to the TKE console and perform node-pool-related operations based on the following documents:

• Creating a Node Pool
• Viewing a Node Pool
• Adjusting a Node Pool
• Deleting a Node Pool