Split out node metrics into reference section
This commit is contained in:
Tim Bannister
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---
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title: Node metrics data
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content_type: reference
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weight: 50
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description: >-
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Mechanisms for accessing metrics at node, volume, pod and container level,
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as seen by the kubelet.
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---
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The [kubelet](/docs/reference/command-line-tools-reference/kubelet/)
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gathers metric statistics at the node, volume, pod and container level,
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and emits this information in the
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[Summary API](https://github.com/kubernetes/kubernetes/blob/7d309e0104fedb57280b261e5677d919cb2a0e2d/staging/src/k8s.io/kubelet/pkg/apis/stats/v1alpha1/types.go).
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You can send a proxied request to the stats summary API via the
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Kubernetes API server.
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Here is an example of a Summary API request for a node named `minikube`:
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```shell
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kubectl get --raw "/api/v1/nodes/minikube/proxy/stats/summary"
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```
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Here is the same API call using `curl`:
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```shell
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# You need to run "kubectl proxy" first
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# Change 8080 to the port that "kubectl proxy" assigns
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curl http://localhost:8080/api/v1/nodes/minikube/proxy/stats/summary
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```
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{{< note >}}
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Beginning with `metrics-server` 0.6.x, `metrics-server` queries the `/metrics/resource`
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kubelet endpoint, and not `/stats/summary`.
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{{< /note >}}
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## Summary metrics API source {#summary-api-source}
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By default, Kubernetes fetches node summary metrics data using an embedded
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[cAdvisor](https://github.com/google/cadvisor) that runs within the kubelet.
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## Summary API data via CRI {#pod-and-container-stats-from-cri}
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{{< feature-state for_k8s_version="v1.23" state="alpha" >}}
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If you enable the `PodAndContainerStatsFromCRI`
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[feature gate](/docs/reference/command-line-tools-reference/feature-gates/) in your
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cluster, and you use a container runtime that supports statistics access via
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{{< glossary_tooltip term_id="cri" text="Container Runtime Interface">}} (CRI), then
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the kubelet fetches Pod- and container-level metric data using CRI, and not via cAdvisor.
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## {{% heading "whatsnext" %}}
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The task pages for [Troubleshooting Clusters](/docs/tasks/debug/debug-cluster/) discuss
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how to use a metrics pipeline that rely on these data.
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@ -1,4 +1,17 @@
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---
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title: Node Reference Information
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weight: 80
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no_list: true
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---
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This section contains the following reference topics about nodes:
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* the kubelet's [checkpoint API](/docs/reference/node/kubelet-checkpoint-api/)
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* a list of [Articles on dockershim Removal and on Using CRI-compatible Runtimes](/docs/reference/node/topics-on-dockershim-and-cri-compatible-runtimes/)
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You can also read node reference details from elsewhere in the
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Kubernetes documentation, including:
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* [Node Metrics Data](/docs/reference/instrumentation/node-metrics).
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@ -232,6 +232,8 @@ to collect metrics from each node. Depending on the metrics-server version it us
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* Metrics resource endpoint `/metrics/resource` in version v0.6.0+ or
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* Summary API endpoint `/stats/summary` in older versions
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## {{% heading "whatsnext" %}}
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To learn more about the metrics-server, see the
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[metrics-server repository](https://github.com/kubernetes-sigs/metrics-server).
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@ -243,44 +245,5 @@ You can also check out the following:
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* [metrics-server releases](https://github.com/kubernetes-sigs/metrics-server/releases)
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* [Horizontal Pod Autoscaling](/docs/tasks/run-application/horizontal-pod-autoscale/)
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## Node metrics data
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The [kubelet](/docs/reference/command-line-tools-reference/kubelet/)
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gathers metric statistics at the node, volume, pod and container level,
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and emits this information in the
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[Summary API](https://github.com/kubernetes/kubernetes/blob/7d309e0104fedb57280b261e5677d919cb2a0e2d/staging/src/k8s.io/kubelet/pkg/apis/stats/v1alpha1/types.go).
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You can send a proxied request to the stats summary API via the
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Kubernetes API server.
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Here is an example of a Summary API request for a node named `minikube`:
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```shell
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kubectl get --raw "/api/v1/nodes/minikube/proxy/stats/summary"
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```
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Here is the same API call using `curl`:
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```shell
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curl http://localhost:8080/api/v1/nodes/minikube/proxy/stats/summary
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```
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{{< note >}}
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Beginning with `metrics-server` 0.6.x, `metrics-server` queries the `/metrics/resource`
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kubelet endpoint, and not `/stats/summary`.
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{{< /note >}}
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### Summary metrics API source {#summary-api-source}
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By default, Kubernetes fetches node summary metrics data using an embedded
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[cAdvisor](https://github.com/google/cadvisor) that runs with in the kubelet.
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### Summary API data via CRI {#pod-and-container-stats-from-cri}
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{{< feature-state for_k8s_version="v1.23" state="alpha" >}}
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If you enable the `PodAndContainerStatsFromCRI`
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[feature gate](/docs/reference/command-line-tools-reference/feature-gates/) in your
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cluster, and you use a container runtime that supports statistics access via
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{{< glossary_tooltip term_id="cri" text="Container Runtime Interface">}} (CRI), then
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the kubelet fetches Pod- and container-level metric data using CRI, and not via cadvisor.
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To learn about how the kubelet serves node metrics, and how you can access those via
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the Kubernetes API, read [Node Metrics Data](/docs/reference/instrumentation/node-metrics).
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