Help Center/ Ubiquitous Cloud Native Service/ User Guide/ UCS Clusters/ Single-Cluster Management/ Nodes/ Adding Labels/Taints to Nodes
Updated on 2024-06-17 GMT+08:00
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Adding Labels/Taints to Nodes

UCS allows you to add different labels to nodes to define different node attributes. By using these labels, you can quickly understand the characteristics of each node.

Taints enable a node to repel specific pods to prevent these pods from being scheduled to the node, achieving reasonable allocation of workloads on nodes.

Node Label Usage Scenarios

Node labels are mainly used in the following scenarios:

  • Node classification: Node labels are used to classify nodes.
  • Affinity and anti-affinity between workloads and nodes:
    • Different workloads have different resource requirements such as CPU, memory, and I/O. If a workload consumes too many resources in a cluster, other workloads in the same cluster may fail to run properly. In this case, you are advised to add different labels to nodes. When deploying a workload, you can configure node affinity and anti-affinity based on node labels.
    • A system can be divided into multiple modules. Each module consists of multiple microservices. To ensure efficient O&M, you can add a module label to each node so that workloads in each module can be deployed on the corresponding node. In this way, workloads in modules do not interfere with each other and can be easily maintained on their nodes.

Inherent Node Labels

After a node is created, UCS adds labels to the node. These inherent labels cannot be edited or deleted. Table 1 lists the inherent labels of a node.

Table 1 Inherent labels of a node

Key

Value

failure-domain.beta.kubernetes.io/region

Indicates the region where the node is located.

failure-domain.beta.kubernetes.io/zone

Indicates the AZ where the node is located.

beta.kubernetes.io/arch

Indicates the processor architecture of the node.

For example, amd64 indicates a AMD64-bit processor.

beta.kubernetes.io/os

Indicates the operating system of the node.

For example, linux indicates that the node uses Linux as its operating system.

kubernetes.io/availablezone

Indicates the AZ where the node is located.

kubernetes.io/hostname

Indicates the host name of the node.

os.architecture

Indicates the processor architecture of the node.

For example, amd64 indicates a AMD64-bit processor.

os.name

Indicates the operating system name of the node.

For example, EulerOS_2.0_SP2 indicates that the node uses EulerOS 2.2 as its operating system.

os.version

Indicates the kernel version of the node.

Taint

Taints are in the format of Key=Value:Effect. Key and Value are the labels of a taint. Value can be empty. Effect is used to describe the effect of taints. The following options are supported for Effect:
  • NoSchedule: No pod will be able to schedule onto the node unless it has a matching toleration, but existing pods will not be evicted from the node.
  • NoExecute: Pods that cannot tolerate this taint cannot be scheduled onto the node, and existing pods will be evicted from the node.

Toleration

Tolerations are applied to pods, and allow (but do not require) the pods to schedule onto nodes with matching taints.

Taints and tolerations work together to ensure that pods are not scheduled onto inappropriate nodes. One or more taints are applied to a node. This marks that the node should not accept any pods that do not tolerate the taints.

Example:

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  labels:
    env: test
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
  tolerations:
  - key: "key1"
    operator: "Equal"
    value: "value1"
    effect: "NoSchedule"

In the preceding toleration label, key is key1, value is value1, and effect is NoSchedule. Therefore, the pod can be scheduled to the corresponding node.

The tolerance can also be set as follows, indicating that when a taint whose key is key1 and effect is NoSchedule exists on a node, the pod can also be scheduled to the corresponding node.

tolerations:
- key: "key1"
  operator: "Exists"
  effect: "NoSchedule"

Managing Node Labels/Taints

  1. Access the cluster details page.
  2. In the navigation pane, choose Nodes, select the target node, and click Manage Labels and Taints.
  3. Click to add a node label or taint. You can add a maximum of 10 operations at a time.

    Figure 1 Adding labels or taints
    • Choose Add/Update or Delete.
    • Set the operation object to Kubernetes Label or Taint.
    • Specify Key and Value.
    • If you choose Taint, select a taint effect. For details, see Taint.

  4. Click OK.

Parent topic: Nodes