reload: preserve configuration path during hot reload

[antonio]

Hot reload now preserves the directory of the main configuration when it creates the replacement context.

Fluent Bit uses this path to resolve relative service file references. Startup sets the path correctly, but reload creates a fresh context without carrying it over. As a result, relative Parsers_File and Plugins_File references that work at startup fail during reload.

Copying the path before loading the new configuration allows the existing path resolution to work unchanged. This also adds regression coverage for relative parser paths in both classic and YAML configurations.

Disclosure: I developed this change with AI assistance. I have not written C code in more than 20 years, so I would appreciate particular scrutiny of the memory ownership, cleanup paths, and conformity with Fluent Bit’s conventions.

Fixes #12333

Summary by CodeRabbit

• Bug Fixes

  • Improved hot-reload reliability for configurations using relative parser files.
  • Preserved the active configuration path during reloads.
  • Added safer cleanup and watchdog handling when reloads cannot be completed.
  • Ensured parser files remain available and load correctly after configuration replacement.

• Tests

  • Expanded hot-reload coverage for classic and YAML configurations.
  • Added validation of parser loading before and after reloads.
  • Added coverage for halted reload scenarios and configuration path handling.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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• tests/internal/reload.c

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📝 Walkthrough

Walkthrough

Hot reload now preserves the main configuration directory when creating a new configuration. Integration and internal tests verify relative parser files after startup and HTTP-triggered reloads.

Changes

Hot reload relative path handling

Layer / File(s)	Summary
Preserve configuration directory during reload src/flb_reload.c	The reload path copies conf_path into the new configuration. Allocation failure performs cleanup, stops the watchdog, and returns FLB_RELOAD_HALTED.
Cover relative parser files through HTTP reload tests/integration/scenarios/hot_reload_watch/config/*, tests/integration/scenarios/hot_reload_watch/tests/test_hot_reload_watch_001.py	The integration test stages a relative parser file beside classic and YAML runtime configurations. It validates initial parsing, disabled automatic reload, HTTP reload, and updated output.
Validate parser preservation in internal reload tests tests/internal/data/reload/*, tests/internal/reload.c	The internal test loads reload_test, configures conf_path, and verifies parser availability and path preservation after reload. It asserts reload status and reports failures.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 39aa8

Hot reload now preserves the configuration directory so relative parser and plugin references resolve consistently with startup; the replacement context is independently owned and cleaned up on pre-replacement failures, and no actionable merge-blocking risk remains.

Suggested reviewers: edsiper

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 11.11% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the primary change: preserving the configuration path during hot reload.
Linked Issues check	✅ Passed	The implementation copies old_config->conf_path into the replacement context. The integration and internal tests cover relative parser files in classic and YAML configurations, which addresses the rel…
Out of Scope Changes check	✅ Passed	All changes support issue [#12333]. The source change preserves the configuration directory, and the added tests and configuration files verify relative parser resolution during hot reload.

Full details: Linked Issues check

Explanation

The implementation copies old_config->conf_path into the replacement context. The integration and internal tests cover relative parser files in classic and YAML configurations, which addresses the relative-path resolution failure described in issue [#12333].

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[cosmo0920]

Thanks for your work.
It's a really good first step to mitigate handling relative paths during hot-reloading.

I found an issue on a testing assertion.
Could you address on it?