Node metrics data [page]deterministic

The [kubelet](/docs/reference/command-line-tools-reference/kubelet/) gathers metric statistics at the node, volume, pod and container level, and emits this information in the [Summary API](/docs/reference/config-api/kubelet-stats.v1alpha1/).

You can send a proxied request to the stats summary API via the Kubernetes API server.

Here is an example of a Summary API request for a node named `minikube`:

```shell kubectl get --raw "/api/v1/nodes/minikube/proxy/stats/summary" ```

Here is the same API call using `curl`:

```shell # You need to run "kubectl proxy" first # Change 8080 to the port that "kubectl proxy" assigns curl http://localhost:8080/api/v1/nodes/minikube/proxy/stats/summary ```

> Note: Beginning with `metrics-server` 0.6.x, `metrics-server` queries the `/metrics/resource` kubelet endpoint, and not `/stats/summary`.

## Summary metrics API source {#summary-api-source}

By default, Kubernetes fetches node summary metrics data using an embedded [cAdvisor](https://github.com/google/cadvisor) that runs within the kubelet. If you enable the `PodAndContainerStatsFromCRI` [feature gate](/docs/reference/command-line-tools-reference/feature-gates/) in your cluster, and you use a container runtime that supports statistics access via [Container Runtime Interface](#gloss:cri) (CRI), then the kubelet [fetches Pod- and container-level metric data using CRI](/docs/reference/instrumentation/cri-pod-container-metrics), and not via cAdvisor.

## Pressure Stall Information (PSI) {#psi}

As a stable feature, Kubernetes lets you configure kubelet to collect Linux kernel [Pressure Stall Information](https://docs.kernel.org/accounting/psi.html) (PSI) for CPU, memory, and I/O usage. The information is collected at node, pod and container level. See [Summary API](/docs/reference/config-api/kubelet-stats.v1alpha1/) for detailed schema. Starting with Kubernetes v.1.36, the `KubeletPSI` [feature gate](/docs/reference/command-line-tools-reference/feature-gates/) is locked to true and cannot be disabled. The information is also exposed in [Prometheus metrics](/docs/concepts/cluster-administration/system-metrics#psi-metrics).

You can learn how to interpret the PSI metrics in [Understand PSI Metrics](/docs/reference/instrumentation/understand-psi-metrics/).

### Requirements

Pressure Stall Information requires:

• [Linux kernel versions 4.20 or later](/docs/reference/node/kernel-version-requirements#requirements-psi).
• [cgroup v2](/docs/concepts/architecture/cgroups)

##

The task pages for [Troubleshooting Clusters](/docs/tasks/debug/debug-cluster/) discuss how to use a metrics pipeline that rely on these data.