Diskstats/size bytes ci fix

[anulika-asama]

Summary by CodeRabbit

• New Features
  • Disk information metrics now include a size_bytes label for block devices.
  • New kernel modules collector exposing per-module metrics including size, refcount, and state.

[coderabbitai]

Walkthrough

The PR adds a size_bytes label to the existing node_disk_info metric by reading sysfs block device size in diskstats_linux.go, with test and fixture updates. It also introduces a new kernelmodules collector in kernelmodules_linux.go that parses /proc/modules and emits per-module state, size, and refcount gauges. Minor housekeeping edits (license header, blank line) are also included.

Changes

diskstats size_bytes label

Layer / File(s)	Summary
Descriptor, sysfs read, emission, tests, and fixtures collector/diskstats_linux.go, collector/diskstats_linux_test.go, collector/fixtures/sys.ttar	Adds size_bytes to infoDesc label names, reads each device's block size from sysfs in Update with os.IsNotExist and debug-log fallback, passes the value to mustNewConstMetric, updates golden test expectations for all devices, adds the sys/block/sda/size fixture entry, and relocates NVMe fixture entries.

kernelmodules collector

Layer / File(s)	Summary
Struct, init registration, and constructor collector/kernelmodules_linux.go	Defines kernelModulesCollector with moduleStateDesc, moduleSizeDesc, and moduleRefcountDesc Prometheus descriptors plus a *slog.Logger; registers NewKernelModulesCollector via init(); constructor builds all three descriptors with a module label.
Update: /proc/modules parsing and metric emission collector/kernelmodules_linux.go	Opens /proc/modules with a bufio.Scanner, parses size and refcount as floats, maps Live/Loading/Unloading state strings to 1/0/-1, skips malformed lines with a warning log, emits three gauge metrics per module, and returns scanner.Err().

Sequence Diagram(s)

sequenceDiagram
  participant Prometheus
  participant kernelModulesCollector
  participant procModules as /proc/modules

  Prometheus->>kernelModulesCollector: Update(ch)
  kernelModulesCollector->>procModules: Open and scan lines
  loop per module line
    procModules-->>kernelModulesCollector: name, size, refcount, state fields
    kernelModulesCollector->>kernelModulesCollector: parse size/refcount, map state string→numeric
    kernelModulesCollector->>Prometheus: emit state gauge (module label)
    kernelModulesCollector->>Prometheus: emit size_bytes gauge (module label)
    kernelModulesCollector->>Prometheus: emit refcount gauge (module label)
  end
  kernelModulesCollector-->>Prometheus: return scanner.Err()

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 Hop hop, the disk now tells its size,
A sysfs read before your eyes.
And kernel modules? Now they speak—
Live, Loading, Unloading, peek!
Three gauges bloom from /proc/modules bright,
The rabbit checks the metrics 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 title references a main change (diskstats and size_bytes) present in the changeset, though it uses informal language ('ci fix') that is somewhat unclear.
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-ci-fix

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

collector/kernelmodules_linux.go (1)

79-80: 🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

Increase scanner token limit to avoid scrape-time failure on long /proc/modules lines.

bufio.Scanner uses a 64 KiB token cap by default. If a module line exceeds that, scanning aborts and Update returns an error (collector scrape failure). Set a larger buffer explicitly at scanner initialization.

Suggested patch

 	scanner := bufio.NewScanner(file)
+	// /proc/modules lines are typically short, but raise the token limit defensively
+	// so one oversized line doesn't fail the entire collector scrape.
+	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
 	for scanner.Scan() {

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@collector/kernelmodules_linux.go` around lines 79 - 80, The bufio.Scanner at
the scanner initialization point in kernelmodules_linux.go uses the default 64
KiB token limit, which can cause scanning to fail if lines in /proc/modules
exceed this size and result in collector scrape errors. After creating the
scanner with bufio.NewScanner, call the scanner.Buffer method to set a larger
maximum token size to accommodate longer module lines and prevent scrape-time
failures.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@collector/kernelmodules_linux.go`:
- Around line 79-80: The bufio.Scanner at the scanner initialization point in
kernelmodules_linux.go uses the default 64 KiB token limit, which can cause
scanning to fail if lines in /proc/modules exceed this size and result in
collector scrape errors. After creating the scanner with bufio.NewScanner, call
the scanner.Buffer method to set a larger maximum token size to accommodate
longer module lines and prevent scrape-time failures.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 95fd258c-62a1-4aed-8584-285e6bbd47a7

📥 Commits

Reviewing files that changed from the base of the PR and between d5f39dc and 9e58579.

📒 Files selected for processing (6)

• collector/diskstats_linux.go
• collector/diskstats_linux_test.go
• collector/fixtures/sys.ttar
• collector/kernelmodules_linux.go
• collector/systemdservices_linux.go
• node_exporter.go

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

• collector/fixtures/sys.ttar