♻️ Refactor: Reduce the Memory Usage of ignoreHeaders

[ksw2000]

Description

When the value of a map is not used, using struct{} instead of any can significantly reduce memory usage. The following experiment demonstrates the improvement:

• Go 1.24: Memory usage reduced from 616 bytes to 456 bytes. (-26%)
• Go 1.23: Memory usage reduced from 576 bytes to 288 bytes. (-50%)

This change helps optimize memory consumption, making it more efficient when the value is not needed.

Go 1.24 introduced optimizations in the map implementation, further affecting memory consumption.

func main() {
	before := getMemUsage()
	ignoreHeaders := map[string]any{
		"Connection":          nil,
		"Keep-Alive":          nil,
		"Proxy-Authenticate":  nil,
		"Proxy-Authorization": nil,
		"TE":                  nil,
		"Trailers":            nil,
		"Transfer-Encoding":   nil,
		"Upgrade":             nil,
		"Content-Type":        nil,
		"Content-Encoding":    nil,
	}
	after := getMemUsage()
	fmt.Printf("Map memory usage: %d bytes\n", after-before)
	delete(ignoreHeaders, "")
}

func getMemUsage() uint64 {
	var m runtime.MemStats
	runtime.ReadMemStats(&m)
	return m.Alloc
}

• In go 1.23: 576 bytes
• In go 1.24: 616 bytes

func main() {
	before := getMemUsage()
	ignoreHeaders := map[string]struct{}{
		"Connection":          {},
		"Keep-Alive":          {},
		"Proxy-Authenticate":  {},
		"Proxy-Authorization": {},
		"TE":                  {},
		"Trailers":            {},
		"Transfer-Encoding":   {},
		"Upgrade":             {},
		"Content-Type":        {},
		"Content-Encoding":    {},
	}
	after := getMemUsage()
	fmt.Printf("Map memory usage: %d bytes\n", after-before)
	delete(ignoreHeaders, "")
}

func getMemUsage() uint64 {
	var m runtime.MemStats
	runtime.ReadMemStats(&m)
	return m.Alloc
}

• In go 1.23: 288 bytes
• In go 1.24: 456 bytes

Type of change

Please delete options that are not relevant.

• Performance improvement (non-breaking change which improves efficiency)
• Code consistency (non-breaking change which improves code reliability and robustness)

Checklist

Before you submit your pull request, please make sure you meet these requirements:

• Followed the inspiration of the Express.js framework for new functionalities, making them similar in usage.
• Conducted a self-review of the code and provided comments for complex or critical parts.
• Updated the documentation in the /docs/ directory for Fiber's documentation.
• Added or updated unit tests to validate the effectiveness of the changes or new features.
• Ensured that new and existing unit tests pass locally with the changes.
• Verified that any new dependencies are essential and have been agreed upon by the maintainers/community.
• Aimed for optimal performance with minimal allocations in the new code.
• Provided benchmarks for the new code to analyze and improve upon.

[coderabbitai]

Walkthrough

The pull request alters a variable declaration in the cache middleware. The ignoreHeaders variable in middleware/cache/cache.go now uses a map with empty struct values instead of the any type. This change refines the data structure to improve memory efficiency while leaving the caching functionality and behavior unchanged.

Changes

File(s)	Change Summary
middleware/cache/cache.go	Changed type of ignoreHeaders from map[string]any to map[string]struct{} to optimize memory usage by using empty struct values.

Poem

Hoppin' in code, I twirl with glee,
Changing headers now set free.
Maps refined with empty grace,
Memory saved in every space.
A rabbit cheers each smart decree! 🐰✨

---

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📥 Commits

Reviewing files that changed from the base of the PR and between 4b62d3d and 157731b.

📒 Files selected for processing (1)

• middleware/cache/cache.go (1 hunks)

✅ Files skipped from review due to trivial changes (1)

• middleware/cache/cache.go

⏰ Context from checks skipped due to timeout of 90000ms (5)

• GitHub Check: unit (1.23.x, macos-13)
• GitHub Check: unit (1.23.x, windows-latest)
• GitHub Check: Compare
• GitHub Check: Analyse
• GitHub Check: repeated

---

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.14%. Comparing base (4b62d3d) to head (2cd8495).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3322      +/-   ##
==========================================
- Coverage   84.21%   84.14%   -0.07%     
==========================================
  Files         116      116              
  Lines       11558    11558              
==========================================
- Hits         9734     9726       -8     
- Misses       1395     1401       +6     
- Partials      429      431       +2     

Flag	Coverage Δ
unittests	84.14% <ø> (-0.07%)	⬇️

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[gaby]

👍 LGTM, great find!