Frontend Asset Optimization

[akshayutture-augment]

Test 8

---

Replicated from ai-code-review-evaluation/grafana-greptile#8

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[akshayutture-augment]

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Greptile Overview

Confidence Score: 2/5

• this PR partially fixes the data race but introduces an incomplete double-check locking pattern
• while the addition of sync.RWMutex prevents the data race, the implementation is flawed - missing re-check after acquiring write lock allows multiple goroutines to redundantly load assets and overwrite the cache
• pkg/api/webassets/webassets.go requires attention to fix the double-check locking issue

Important Files Changed

File Analysis

Filename	Score	Overview
pkg/api/webassets/webassets.go	2/5	added sync.RWMutex to fix data race, but double-check locking pattern is incomplete

Sequence Diagram

sequenceDiagram
    participant C1 as Goroutine 1
    participant C2 as Goroutine 2
    participant M as RWMutex
    participant Cache as entryPointAssetsCache
    participant FS as File System

    Note over C1,C2: Both check cache simultaneously
    C1->>M: RLock()
    C2->>M: RLock()
    C1->>Cache: Read (nil)
    C2->>Cache: Read (nil)
    C1->>M: RUnlock()
    C2->>M: RUnlock()
    
    Note over C1,C2: Both proceed to load assets
    C1->>M: Lock()
    C1->>FS: Read assets-manifest.json
    FS-->>C1: Return assets
    C1->>Cache: Write assets
    C1->>M: Unlock()
    
    C2->>M: Lock() [waits]
    Note over C2: Missing re-check here!
    C2->>FS: Read assets-manifest.json (redundant)
    FS-->>C2: Return assets
    C2->>Cache: Overwrite assets
    C2->>M: Unlock()

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_{1 file reviewed, 1 comment}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

logic: missing double-check after acquiring write lock - multiple goroutines can populate cache simultaneously

Suggested change

	entryPointAssetsCacheMu.Lock()
	defer entryPointAssetsCacheMu.Unlock()
	entryPointAssetsCacheMu.Lock()
	defer entryPointAssetsCacheMu.Unlock()
	// Re-check after acquiring write lock
	if cfg.Env != setting.Dev && entryPointAssetsCache != nil {
	return entryPointAssetsCache, nil
	}

Prompt To Fix With AI

This is a comment left during a code review.
Path: pkg/api/webassets/webassets.go
Line: 48:49

Comment:
**logic:** missing double-check after acquiring write lock - multiple goroutines can populate cache simultaneously

```suggestion
	entryPointAssetsCacheMu.Lock()
	defer entryPointAssetsCacheMu.Unlock()
	
	// Re-check after acquiring write lock
	if cfg.Env != setting.Dev && entryPointAssetsCache != nil {
		return entryPointAssetsCache, nil
	}
```

How can I resolve this? If you propose a fix, please make it concise.