Kubernetes Metrics Server

From version 1.8 onwards, Kubernetes provides resource usage metrics, such as the container CPU and memory usage, through the Metrics API. These metrics can be directly accessed by users (for example, by using the kubectl top command) or used by controllers (for example, Horizontal Pod Autoscaler) in a cluster for decision-making. The specific component is metrics-server, which is used to substitute for heapster for providing the similar functions. heapster has been gradually abandoned since v1.11.

metrics-server is an aggregator for monitoring data of core cluster resources. You can quickly install this add-on on the CCE console.

After installing this add-on, you can create HPA policies. For details, see HPA Policies.

The official community project and documentation are available at https://github.com/kubernetes-sigs/metrics-server.

Installing the Add-on

Log in to the CCE console and click the cluster name to access the cluster console. Choose Add-ons in the navigation pane, locate Kubernetes Metrics Server on the right, and click Install.

On the Install Add-on page, configure the specifications.

**Table 1** metrics-server configuration
Parameter	Description
Add-on Specifications	Select Single, Custom, or HA for Add-on Specifications.
Instances	Number of pods that will be created to match the selected add-on specifications. If you select Custom, you can adjust the number of pods as required.
Containers	CPU and memory quotas of the container allowed for the selected add-on specifications. If you select Custom, you can adjust the container specifications as required.

Configure scheduling policies for the add-on.

Scheduling policies do not take effect on add-on instances of the DaemonSet type.
When configuring multi-AZ deployment or node affinity, ensure that there are nodes meeting the scheduling policy and that resources are sufficient in the cluster. Otherwise, the add-on cannot run.

**Table 2** Configurations for add-on scheduling
Parameter	Description
Multi-AZ Deployment	Preferred: Deployment pods of the add-on will be preferentially scheduled to nodes in different AZs. If all the nodes in the cluster are deployed in the same AZ, the pods will be scheduled to that AZ. Forcible: Deployment pods of the add-on will be forcibly scheduled to nodes in different AZs. If there are fewer AZs than pods, the extra pods will fail to run.
Node Affinity	Incompatibility: Node affinity is disabled for the add-on. Node Affinity: Specify the nodes where the add-on is deployed. If you do not specify the nodes, the add-on will be randomly scheduled based on the default cluster scheduling policy. Specified Node Pool Scheduling: Specify the node pool where the add-on is deployed. If you do not specify the node pool, the add-on will be randomly scheduled based on the default cluster scheduling policy. Custom Policies: Enter the labels of the nodes where the add-on is to be deployed for more flexible scheduling policies. If you do not specify node labels, the add-on will be randomly scheduled based on the default cluster scheduling policy. If multiple custom affinity policies are configured, ensure that there are nodes that meet all the affinity policies in the cluster. Otherwise, the add-on cannot run.
Taints and Tolerations	Using both taints and tolerations allows (not forcibly) the add-on Deployment to be scheduled to a node with the matching taints, and controls the Deployment eviction policies after the node where the Deployment is located is tainted. The add-on adds the default tolerance policy for the node.kubernetes.io/not-ready and node.kubernetes.io/unreachable taints, respectively. The tolerance time window is 60s. For details, see Taints and Tolerations.

Click Install.

Components

**Table 3** metrics-server components
Component	Description	Resource Type
metrics-server	Aggregator for the monitored data of cluster core resources, which is used to collect and aggregate resource usage metrics obtained through the Metrics API in the cluster	Deployment