out_kafka: add add_timestamp option to suppress timestamp field

[piyushka-ally]

The Kafka output plugin unconditionally injects an @timestamp field into every record when using json or msgpack formats. This prevents users from piping data through Fluent Bit into downstream Kafka consumers (e.g. JDBC sink connector) that enforce a strict schema, as the extra field causes schema mismatch errors.

Add a new boolean config option add_timestamp (default: true) that controls whether the timestamp field is injected into the output record. When set to false, the field is omitted entirely.

This is fully backward compatible — existing configurations are unaffected since the option defaults to true.

Example usage to disable timestamp injection:

[OUTPUT]
    Name          kafka
    Match         *
    Brokers       localhost:9092
    Topics        my-topic
    add_timestamp false

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Testing
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Documentation

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Backporting

• [N/A] Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• New Features
  • Added add_timestamp configuration option to the Kafka output plugin
  • Timestamp fields are now appended to records by default
  • Can be disabled to suppress timestamp fields and reduce message size

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a7ab491f-83b5-4f5c-88ab-124741e8d18d

📥 Commits

Reviewing files that changed from the base of the PR and between 962855c and 8e33e89.

📒 Files selected for processing (2)

• plugins/out_kafka/kafka.c
• plugins/out_kafka/kafka_config.h

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📝 Walkthrough

Walkthrough

The pull request introduces a new configuration option add_timestamp (default true) to the Kafka output plugin. This option conditionally appends a timestamp field to records, with the message-building logic and struct definition adjusted to support this feature.

Changes

Cohort / File(s)	Summary
Kafka Timestamp Configuration plugins/out_kafka/kafka.c, plugins/out_kafka/kafka_config.h	Introduces add_timestamp boolean configuration option (default true) to conditionally append timestamp fields to Kafka records. Updates struct field definition and adjusts message-building logic for JSON/MSG formats to conditionally allocate space and emit timestamp based on configuration flag.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~15 minutes

Poem

🐰 Tick-tock, a timestamp takes flight,
A config toggle, shining bright!
Messages dance through Kafka streams,
With time-stamped dreams or timeless schemes. ⏰✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding an add_timestamp option to the Kafka output plugin to allow suppressing the timestamp field.

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✨ Finishing Touches

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• Create PR with unit tests

📝 Coding Plan

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