docs: buffering: document memrb storage type and improve coverage

[eschabell]

• Add memory ring buffer (memrb) as third buffering mode section
• Update intro from "two modes" to "three modes"
• Add memrb as accepted value for per-input storage.type
• Add memrb configuration examples in YAML and classic formats
• Document memrb_dropped_chunks and memrb_dropped_bytes metrics
• Add note about storage.inherit and global storage.type usage
• Sort per-input settings table alphabetically by key

Fixes #2373

Summary by CodeRabbit

• Documentation
  • Documented a new memory ring buffer (memrb) buffering mode for high-throughput scenarios, explaining its drop-when-full behavior
  • Added metrics to track dropped chunks and dropped bytes in memrb mode
  • Updated configuration guidance and examples to include memrb as a valid storage.type and show inheritance/override of default buffering
  • Clarified mem_buf_limit semantics and example configurations for all three buffering modes

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📝 Walkthrough

Walkthrough

Adds a new memory ring buffer mode ("memrb") to buffering documentation, expands buffering modes to three (memory-only, memrb, filesystem), documents memrb behavior and metrics, updates configuration reference and examples, and adds guidance for global/per-input storage.type inheritance.

Changes

Cohort / File(s)	Summary
Buffering Documentation pipeline/buffering.md	Introduce memrb storage.type; describe fixed-size in-memory ring semantics and automatic dropping of oldest chunks when full; add memrb_dropped_chunks and memrb_dropped_bytes metrics; update mem_buf_limit and storage.type docs, global/per-input inheritance examples, and YAML/fluent-bit.conf examples to include memrb.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• consolidate backpressure/buffering info #2324: Prior changes to pipeline/buffering.md and buffering semantics that this PR extends with the memrb mode.

Suggested reviewers

• cosmo0920
• esmerel

Poem

🐰 Soft rings of memory, round and bright,
Old chunks step aside for new delight,
Metrics count what time lets go,
Docs explain the steady flow,
Hop along — the buffer's light! ✨

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title clearly and concisely summarizes the main change: documenting the memrb storage type and improving buffering documentation coverage.
Linked Issues check	✅ Passed	The PR addresses all objectives from issue #2373: documents memrb mode, provides configuration examples in YAML and classic formats, includes new metrics (memrb_dropped_chunks and memrb_dropped_bytes), and clarifies storage.inherit behavior.
Out of Scope Changes check	✅ Passed	All changes are within scope of documenting the memrb buffering mode and improving buffering coverage. The alphabetical sorting of the per-input settings table is a minor organizational improvement directly supporting better documentation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Merge Conflict Detection	✅ Passed	✅ No merge conflicts detected when merging into master

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[Copilot]

Pull request overview

This PR enhances the Fluent Bit buffering documentation by adding comprehensive coverage for the memory ring buffer (memrb) storage type, which joins memory-only and filesystem as the third buffering mode. The documentation now accurately reflects that Fluent Bit supports three buffering modes rather than two, and provides detailed information about memrb's behavior, configuration, and monitoring capabilities.

Changes:

• Updated buffering modes introduction to describe three modes instead of two
• Added new "Memory ring buffer buffering" section explaining memrb behavior and use cases
• Updated storage.type parameter documentation to include memrb as an accepted value
• Added memrb configuration examples in both YAML and classic formats
• Documented memrb-specific metrics (memrb_dropped_chunks and memrb_dropped_bytes)
• Added note about storage.inherit and global storage.type configuration

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[coderabbitai]

Actionable comments posted: 2

🤖 Fix all issues with AI agents

In `@pipeline/buffering.md`:
- Line 92: The doc text for mem_buf_limit conflicts with examples referencing
storage.type: memrb; update the description of mem_buf_limit to state explicitly
whether it applies to memory-only buffering and/or memrb mode. Modify the
paragraph for the `mem_buf_limit` entry so it clarifies scope (e.g., "If
memory-only buffering or memrb storage is used, sets a limit..."), mention that
the value must follow unit size specs, and keep the default behavior note
(unspecified means no limit). Ensure references to `mem_buf_limit` and
`storage.type: memrb` in examples remain consistent with this new description.
- Around line 84-85: Remove the incorrect reference to storage.inherit in the
service section and update the sentence to accurately explain buffering
defaults: state that you set a global default by configuring storage.type in the
service section and that input plugins that do not explicitly set their own
storage.type will inherit the global storage.type by default; replace or remove
any mention of storage.inherit and, if helpful, add a short note that per-plugin
buffering is configured via each input's storage.type setting.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

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[eschabell]

@cosmo0920 and @patrick-stephens ready for review!