Expose disk size as size_bytes label on node_disk_info

[anulika-asama]

Summary by CodeRabbit

• New Features

  • Disk information metrics now include a size_bytes label, showing each device’s size in bytes (left empty when size information isn’t available).

• Bug Fixes

  • Updated sysfs fixtures and test expectations to reflect the new disk size label and label ordering.

• Documentation

  • Added Apache 2.0 license headers to the Linux kernel modules and systemd services collectors.

• Chores

  • Minor formatting cleanup in the main entrypoint import block.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: f0d16f97-0f2b-423b-9d66-eb9e92886536

📥 Commits

Reviewing files that changed from the base of the PR and between f86d343 and 459ebf2.

📒 Files selected for processing (3)

• collector/kernelmodules_linux.go
• collector/systemdservices_linux.go
• node_exporter.go

✅ Files skipped from review due to trivial changes (3)

• collector/kernelmodules_linux.go
• node_exporter.go
• collector/systemdservices_linux.go

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Walkthrough

node_disk_info gains a new size_bytes label. The Update method reads per-device block size from sysfs via SysBlockDeviceSize, converts it to a decimal string (empty on missing entries), and passes it to the metric. Test expectations and sysfs fixtures are updated to match.

Changes

Add size_bytes label to node_disk_info

Layer / File(s)	Summary
size_bytes label contract and implementation collector/diskstats_linux.go	infoDesc label list gains size_bytes; Update calls c.fs.SysBlockDeviceSize(dev), logs debug on non-ENOENT errors, converts the result to a base-10 string, and passes it to MustNewConstMetric.
Fixture updates and test expectations collector/fixtures/sys.ttar, collector/diskstats_linux_test.go	Adds sys/block/sda/size (1953525168) to the sysfs fixture, repositions NVMe entries (nvme0c0n0/size, serial, state) to correct archive order, and updates expected node_disk_info samples to include the size_bytes label.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related issues

• Node-exporter bug - expose the size of the disk in node_disk_info metrics #6: This PR directly implements the feature requested in that issue — exposing disk size in node_disk_info by adding a size_bytes label populated from sysfs block device size.

Poem

🐇 A bunny checked sysfs one fine afternoon,
Found block sizes hiding — reported them soon!
size_bytes now shines in the info metric bright,
Each disk's true dimensions brought into the light.
Hops of delight for each sector and byte! 🌟

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a size_bytes label to the node_disk_info metric to expose disk size, which is the primary objective of the PR.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch diskstats/size

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