pipeline: inputs: mqtt: update mqtt input config with buffer_size defaults and payload_key examples

[eschabell]

update mqtt input config with buffer_size defaults and payload_key examples

Fixes #2282.

Summary by CodeRabbit

• Documentation
  • Standardized MQTT input configuration keys to snake_case and updated default values.
  • Clarified buffer_size behavior (messages dropped when over limit) and listener/port defaults.
  • Specified JSON-map requirement for payloads and added guidance on payload_key usage in examples.
  • Added a TLS/SSL configuration subsection and referenced transport security guidance.
  • Updated all example configurations and sample pipelines to reflect the new format.

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[coderabbitai]

Walkthrough

Updated MQTT input documentation: standardized configuration keys to snake_case, added the missing buffer_size option with behavior notes, introduced TLS/SSL guidance, and updated examples to include payload_key and new defaults.

Changes

Cohort / File(s)

Change Summary

MQTT Configuration Documentation pipeline/inputs/mqtt.md

Replaced configuration table with snake_case keys (buffer_size, listen, payload_key, port, threaded) and updated defaults; added Notes on buffer_size behavior (messages dropped when exceeding limit), default listen/port values, and JSON-mapped payload requirement; added TLS/SSL subsection referencing transport security docs; updated "Get started" and pipeline examples to include payload_key: payload and corresponding output mapping.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

• Single documentation file changed; edits are formatting, key renames, added explanatory text and examples.
• Review focus: verify accuracy of defaults, buffer_size semantics, and example consistency.

Poem

🐰 I hopped through docs with a nibble and tap,
snake_case at the burrow — no more camelcap.
Buffer_size cushions the data parade,
TLS keeps things safe in the shady glade.
Payload_key tucked in — now hop, deploy, and clap! 🎉

Pre-merge checks and finishing touches

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title accurately reflects the main changes: updating MQTT input config documentation with buffer_size defaults and payload_key examples.
Linked Issues check	✅ Passed	The PR addresses issue #2282 by adding the missing buffer_size parameter and performing general documentation updates to standardize MQTT input configuration.
Out of Scope Changes check	✅ Passed	All changes are scoped to MQTT input documentation updates: configuration table improvements, buffer_size/payload_key documentation, TLS guidance, and example updates.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

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

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 9714a04 and b2831c2.

📒 Files selected for processing (1)

• pipeline/inputs/mqtt.md (3 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• pipeline/inputs/mqtt.md

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

pipeline/inputs/mqtt.md (1)

17-20: Notes section: clarify non-JSON payload behavior.

The notes are helpful but line 20 ("non-JSON payloads will fail to parse") could be more precise about the impact. Does the message get dropped, or does the entire connection fail?

Please clarify the error handling behavior: for example, "non-JSON payloads will cause the message to be dropped with a warning log."

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between b98e343 and 9714a04.

📒 Files selected for processing (1)

• pipeline/inputs/mqtt.md (3 hunks)

🔇 Additional comments (3)

pipeline/inputs/mqtt.md (3)

22-24: TLS/SSL section appropriately added.

Good addition to reference the Transport Security documentation. This follows the standard pattern used elsewhere in the Fluent Bit documentation.

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61-89: Configuration examples: snake_case and Title_Case formatting is correct.

The YAML example correctly uses snake_case (payload_key on line 68) and the conf format correctly uses Title_Case (Payload_Key on line 84). Both examples properly demonstrate the new payload_key parameter as requested in the issue.

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9-15: Verify that referenced documentation links are valid.

The configuration table structure with snake_case keys and defaults is well-organized. However, ensure the relative links at line 15 (../../administration/multithreading.md#inputs) and line 24 (../../administration/transport-security.md) point to existing documentation pages in the repository.

[eschabell]

AI review passed, merging.