Expose disk size as size_bytes label on node_disk_info

[anulika-asama]

Summary by CodeRabbit

Release Notes

• New Features
  • Disk info metrics now include a size_bytes label displaying the size of each device in bytes, providing enhanced visibility into disk capacity information.

[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: d0206f6c-1058-4ce3-894b-6a3c4a0e87a5

📥 Commits

Reviewing files that changed from the base of the PR and between d5f39dc and f86d343.

📒 Files selected for processing (3)

• collector/diskstats_linux.go
• collector/diskstats_linux_test.go
• collector/fixtures/sys.ttar

👮 Files not reviewed due to content moderation or server errors (1)

• collector/fixtures/sys.ttar

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Walkthrough

The node_disk_info Prometheus metric is extended with a new size_bytes label. The diskstats collector queries per-device block size via SysBlockDeviceSize, tolerates missing entries, and formats the value as a decimal string. The sysfs fixture archive gains a sda/size entry, and test golden strings are updated accordingly.

Changes

node_disk_info size_bytes label

Layer / File(s)	Summary
size_bytes label descriptor, lookup, and metric emission collector/diskstats_linux.go	Adds size_bytes to infoDesc's label list, queries c.fs.SysBlockDeviceSize(dev) in Update with os.IsNotExist tolerance and debug logging on other errors, formats the result as a decimal string, and passes it when emitting the info metric.
Sysfs fixture and test expectations collector/fixtures/sys.ttar, collector/diskstats_linux_test.go	Adds sys/block/sda/size (value 1953525168, mode 664) to the sysfs fixture, reorders NVMe fixture entries, and updates TestDiskStats golden strings to include size_bytes="" or explicit values on every node_disk_info line.

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 requested feature of adding a size_bytes label to the node_disk_info metric populated from sysfs per-device block size.

Poem

🐇 A little rabbit checked the disk one day,
And asked, "How big are you, block device, I pray?"
size_bytes now labels each drive in the list,
From sda to nvme — none shall be missed!
The fixtures all shimmer with values so bright,
The tests run in green, everything is just right. 🌟

🚥 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 pull request title clearly and specifically describes the main change: exposing disk size as a size_bytes label on the node_disk_info metric.
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_bytes

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