Memory Leak in Chi

Memory leaks in Chi applications typically occur through improper handling of request-scoped objects and middleware chains. Since Chi is a lightweight, composable router for Go, memory leaks often manifest in patterns unique to its middleware architecture.

One common vulnerability appears in middleware that captures request context without proper cleanup. Consider this problematic pattern:

type leakyMiddleware struct {
    mu    sync.Mutex
    cache map[string]*requestData
}

func (lm *leakyMiddleware) Middleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        key := r.URL.Path
        lm.mu.Lock()
        if lm.cache == nil {
            lm.cache = make(map[string]*requestData)
        }
        lm.cache[key] = &requestData{time: time.Now()}
        lm.mu.Unlock()
        
        next.ServeHTTP(w, r)
    })
}

This middleware accumulates request data indefinitely, never releasing memory. The cache map grows with every request, causing gradual memory exhaustion.

Another Chi-specific leak pattern involves route handlers that spawn goroutines without proper lifecycle management. Chi's efficient routing can mask these issues:

func leakyHandler() http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        go func() {
            // Background task that never completes
            for {
                // Processing without exit condition
                time.Sleep(1 * time.Second)
            }
        }()
        
        w.WriteHeader(http.StatusOK)
    }
}

Each request spawns an unbounded goroutine, and Chi's non-blocking nature means these accumulate rapidly under load.

Context propagation issues also create leaks. Chi passes context through middleware chains, but improper context cancellation can leave goroutines running:

func contextLeakMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        ctx := context.WithValue(r.Context(), "user", getUserFromDB(r))
        // Missing context cancellation
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

Without proper cancellation, database connections and other resources tied to the context persist beyond the request lifecycle.

Detecting memory leaks in Chi applications requires both runtime monitoring and static analysis. The router's middleware architecture creates specific patterns that can be identified through careful inspection.

Static analysis should focus on middleware chains where context is modified but not cleaned up. Look for patterns like:

func suspiciousMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Context modification without cleanup
        ctx := context.WithValue(r.Context(), "key", expensiveObject())
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

Tools like go vet and staticcheck can flag suspicious context usage, but Chi's patterns require specialized knowledge.

Runtime detection using middleBrick's API security scanner can identify memory leak vulnerabilities through behavioral analysis. The scanner tests for:

• Unbounded goroutine creation in route handlers
• Missing context cancellation in middleware chains
• Persistent state accumulation across requests
• Resource leaks in error handling paths

middleBrick's black-box scanning approach tests the unauthenticated attack surface, making it particularly effective for identifying memory leaks that could be exploited through repeated requests. The scanner can detect gradual memory growth patterns characteristic of leaks.

For Chi applications, middleBrick's OpenAPI analysis is especially valuable. By analyzing your Chi router's OpenAPI spec, it can identify endpoints that might accumulate state or spawn background processes. The scanner tests these endpoints with varying request patterns to observe memory behavior.

Memory leak detection also involves monitoring specific Chi patterns:

// Vulnerable: Missing defer for cleanup
func handlerWithResource() http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        file, _ := os.Open("data.txt")
        // No defer file.Close() - file descriptor leak
        processFile(file)
    }
}

middleBrick's scanning engine can detect these patterns through fuzzing and resource usage monitoring during test requests.

Remediating memory leaks in Chi applications requires understanding both Go's memory management and Chi's middleware architecture. The key is implementing proper cleanup patterns and resource lifecycle management.

For middleware that accumulates state, use request-scoped storage instead of persistent maps:

func safeMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Request-scoped storage - automatically cleaned up
        requestData := make(map[string]interface{})
        ctx := context.WithValue(r.Context(), "requestData", requestData)
        
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

This ensures data is garbage collected after the request completes.

For goroutine management, implement proper cancellation and cleanup:

func safeHandler() http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        ctx, cancel := context.WithCancel(r.Context())
        defer cancel()
        
        go func() {
            select {
            case <-ctx.Done():
                // Clean shutdown
                return
            case <-time.After(5 * time.Second):
                // Task completion
            }
        }()
        
        w.WriteHeader(http.StatusOK)
    }
}

This pattern ensures background tasks don't outlive their parent request.

Context cleanup is critical in Chi middleware chains:

func cleanupMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Store original context for cleanup
        ctx := r.Context()
        
        // Add cleanup function to context
        ctx = context.WithValue(ctx, "cleanup", func() {
            // Release resources, close connections
        })
        
        next.ServeHTTP(w, r.WithContext(ctx))
        
        // Cleanup after response
        if cleanup, ok := ctx.Value("cleanup").(func()); ok {
            cleanup()
        }
    })
}

This ensures resources are released regardless of how the request exits.

For database connections and file handles, use defer statements consistently:

func safeFileHandler() http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        file, err := os.Open("data.txt")
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        defer file.Close() // Guaranteed cleanup
        
        data, err := ioutil.ReadAll(file)
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        
        w.Write(data)
    }
}

middleBrick's remediation guidance includes these specific patterns, helping developers fix memory leaks systematically.