Add new k8s.node.filesystem semantic conventions

[PlateauGao]

Fixes #3858

Changes

This PR proposes adding new Kubernetes node-level filesystem inode capacity and usage metrics under the k8s.node.filesystem namespace:

• k8s.node.filesystem.inode.count (UpDownCounter, {inode}): Represents the total number of inodes in the node's root filesystem.
• k8s.node.filesystem.inode.free (UpDownCounter, {inode}): Represents the number of free inodes in the node's root filesystem.

These metrics are derived from the Kubelet Summary API (v1alpha1.NodeStats.FsStats fields Inodes and InodesFree respectively). Adding these allows monitoring for potential inode pressure or exhaustion on Kubernetes nodes, complementing the existing pod volume inode metrics.

Only the semantic conventions model/ file and corresponding documentation sections have been updated.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Links to prototypes or existing instrumentations (when adding or changing conventions):
  • Kubelet Summary API schema: FsStats.Inodes and FsStats.InodesFree
• Disclose AI usage, see OTel GenAI policy:
  • no AI used
  • AI-assisted
  • bulk AI-generated
• I have the experience and knowledge necessary to understand, review, and validate all content in this PR.¹

Footnotes

1. Yes, I can answer maintainer questions about the content of this PR without using AI. ↩

[Copilot]

Pull request overview

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Adds new semantic conventions and docs for Kubernetes node root filesystem inode metrics, enabling monitoring of inode pressure/exhaustion from Kubelet Summary API data.

Changes:

• Define k8s.node.filesystem.inode.count and k8s.node.filesystem.inode.free in the k8s metrics model.
• Add autogenerated documentation sections and TOC entries for the new metrics.
• Add a changelog entry describing the enhancement.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 5 comments.

File	Description
model/k8s/metrics.yaml	Adds two new node filesystem inode metric definitions under k8s.node.filesystem.*.
docs/system/k8s-metrics.md	Documents the new inode metrics and updates the metrics TOC.
.chloggen/add-k8s-node-inode-metrics.yaml	Adds a release note entry for the new inode metrics.

[PlateauGao]

Hi @ChrsMark, could you please review this PR? Thanks!

[opentelemetry-pr-dashboard]

Pull request dashboard status

Status last refreshed: 2026-07-25 14:01:50 UTC.

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[braydonk]

My approval cannot be official since I'm not part of this group, but I was part of the discussion in the Collector issue on this and confirm it matches my understanding of what we agreed upon there.

[PlateauGao]

Hi @kamphaus , may I have your review here? Thanks