🔥 feat(listen): expose prefork RecoverInterval and ShutdownGracePeriod

[ReneWerner87]

fasthttp v1.72.0 (valyala/fasthttp#2199) added two new knobs to the prefork package. Fiber builds the prefork.Prefork struct internally, so users had no way to set them. This PR exposes both via ListenConfig:

• PreforkRecoverInterval (time.Duration): optional backoff before respawning a crashed child; zero keeps the previous immediate respawn.
• PreforkShutdownGracePeriod (time.Duration): how long the master waits for children after SIGTERM before SIGKILL on shutdown; zero keeps fasthttp's 5s default. Windows children are still killed immediately (fasthttp limitation).

Docs table updated; both fields are exercised in Test_App_Prefork_Master_Process.

🤖 Generated with Claude Code

[coderabbitai]

Walkthrough

Adds two new time.Duration fields, PreforkRecoverInterval and PreforkShutdownGracePeriod, to ListenConfig. These are wired into the prefork.Prefork struct construction in app.prefork, documented in the config table, and set in an existing prefork test.

Changes

Prefork timing configuration

Layer / File(s)	Summary
Config fields and wiring listen.go, prefork.go	ListenConfig gains PreforkRecoverInterval and PreforkShutdownGracePeriod fields with JSON tags; app.prefork passes these through to the prefork.Prefork struct literal alongside existing fields.
Docs and test coverage docs/api/fiber.md, prefork_test.go	Config fields table documents the new options; existing prefork test sets both new fields with sample durations before invoking app.prefork.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related PRs

• gofiber/fiber#4210: Both PRs modify fiber.ListenConfig and the app.prefork path that constructs fasthttp/prefork.Prefork, touching the same configuration-integration points.

Suggested reviewers: sixcolors, efectn, gaby

Poem

A rabbit tweaks the fork with glee,
Two new fields set timers free—
Recover soon, then grace to rest,
Master and child both do their best.
Hop, hop, deploy! 🐇⏱️

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly states the problem, the new fields, docs update, and tests, with only template sections left unfilled.
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.
Title check	✅ Passed	The title clearly summarizes the main change: exposing two prefork settings in ListenConfig.

✨ 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 claude/prefork-knobs-2199

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[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.96%. Comparing base (05919e5) to head (b6a9545).

Files with missing lines	Patch %	Lines
prefork.go	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4491      +/-   ##
==========================================
+ Coverage   92.91%   92.96%   +0.04%     
==========================================
  Files         138      138              
  Lines       13609    13611       +2     
==========================================
+ Hits        12645    12653       +8     
+ Misses        597      592       -5     
+ Partials      367      366       -1     

Flag	Coverage Δ
unittests	92.96% <85.71%> (+0.04%)	⬆️

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[Copilot]

Pull request overview

This PR exposes newly added fasthttp prefork configuration knobs through Fiber’s ListenConfig, allowing callers to control crash-recovery backoff and master shutdown behavior when prefork mode is enabled.

Changes:

• Add PreforkRecoverInterval and PreforkShutdownGracePeriod to ListenConfig.
• Wire the new fields into the internally constructed prefork.Prefork instance.
• Update API docs and extend the existing prefork master-process test setup.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
prefork.go	Plumbs ListenConfig’s new prefork timing fields into prefork.Prefork.
prefork_test.go	Sets the new config fields in the prefork master-process test (but currently doesn’t assert their behavior).
listen.go	Introduces the two new ListenConfig fields with doc comments and JSON tags.
docs/api/fiber.md	Documents the new ListenConfig options in the public API table.