Brummer MCP Server

# Brummer TUI Application - Edge Cases and Testing Analysis ## Executive Summary This analysis identifies critical edge cases, race conditions, and testing gaps in the Brummer TUI application. The codebase shows good concurrent design patterns in some areas but has several potential issues that could lead to race conditions, resource leaks, or inconsistent state. ## 1. Concurrent Access Patterns ### 1.1 Event Bus (pkg/events/events.go) **Potential Issues:** - **Race Condition**: Handler execution in goroutines without synchronization (line 61) - **Memory Leak**: No cleanup for handlers that panic - **Unsubscribe Race**: The Unsubscribe function was referenced in tests but not implemented **Edge Cases:** - Handler panics could leave goroutines hanging - Rapid subscribe/unsubscribe during event publishing - Nil handler functions passed to Subscribe **Recommendations:** ```go // Add panic recovery go func() { defer func() { if r := recover(); r != nil { // Log panic and continue } }() handler(event) }() ``` ### 1.2 Log Store (internal/logs/store.go) **Good Practices:** - Async log processing with channel-based design - Fallback to sync mode on channel overflow - Proper mutex usage for state protection **Potential Issues:** - **Resource Leak**: addChan buffer of 1000 could fill up under heavy load - **Race Condition**: URL map rebuilding during concurrent access - **Deadlock Risk**: Multiple mutex locks in rebuildURLsList (line 574) **Edge Cases:** - Concurrent Add() calls during Close() - URL detection in extremely long log lines - Memory exhaustion with maxEntries set very high ### 1.3 Process Manager (internal/process/manager.go) **Potential Issues:** - **Race Condition**: Process cleanup during concurrent starts (StopProcess vs StartScript) - **Goroutine Leak**: streamLogs goroutines may not exit cleanly on process kill - **Deadlock Risk**: Nested mutex locks in process operations **Edge Cases:** - Killing processes that spawn children rapidly - Port cleanup race when multiple processes use same port - Windows-specific process cleanup edge cases ### 1.4 MCP Connection Manager (internal/mcp/connection_manager.go) **Good Practices:** - Channel-based architecture prevents direct state access - Single goroutine owns all state mutations - Proper cleanup on shutdown **Potential Issues:** - **Deadlock Risk**: Synchronous channel operations without timeouts - **Resource Leak**: HTTP clients not cleaned up on connection failure - **Race Condition**: Concurrent attemptConnection calls for same instance ### 1.5 MCP Streamable Server (internal/mcp/streamable_server.go) **Potential Issues:** - **Memory Leak**: Session cleanup on unexpected disconnects - **Race Condition**: Multiple concurrent websocket writes - **Deadlock Risk**: Nested mutex locks in subscription handling ## 2. Error Handling Edge Cases ### 2.1 Network Failures - **Issue**: HTTP timeouts not consistently handled - **Location**: Various HTTP client operations - **Impact**: Goroutines could hang indefinitely ### 2.2 Process Crashes - **Issue**: Zombie processes on unexpected termination - **Location**: process/manager.go killProcessTree - **Impact**: Resource exhaustion ### 2.3 File System Errors - **Issue**: No handling for disk full scenarios - **Location**: Log writing, configuration saving - **Impact**: Data loss, application crash ### 2.4 Invalid User Input - **Issue**: Regex compilation errors not handled - **Location**: TUI slash commands - **Impact**: Panic in UI thread ## 3. Resource Management ### 3.1 Goroutine Leaks **Identified Locations:** 1. Event bus handlers (no cancellation mechanism) 2. Log streaming goroutines (may not exit on process kill) 3. HTTP request handlers (no request context cancellation) 4. WebSocket connection handlers **Test to Add:** ```go func TestGoroutineLeaks(t *testing.T) { initial := runtime.NumGoroutine() // Run operations // Stop all components time.Sleep(100 * time.Millisecond) final := runtime.NumGoroutine() if final > initial { t.Errorf("Goroutine leak: %d -> %d", initial, final) } } ``` ### 3.2 Channel Deadlocks **Risk Areas:** - Unbuffered channels in synchronous operations - Circular dependencies in channel communications - Missing select statements with timeouts ### 3.3 File Handle Leaks **Locations:** - Process stdout/stderr pipes - Configuration file operations - Log file operations (if implemented) ### 3.4 Memory Leaks **Areas of Concern:** - Circular buffer implementation could retain references - URL map grows without bounds - Session maps not cleaned up properly ## 4. State Synchronization Issues ### 4.1 TUI View Updates **Issues:** - Race between event processing and view rendering - Missing view updates on rapid state changes - Inconsistent state between model and view ### 4.2 Process Status Tracking **Issues:** - Status updates may be lost during rapid transitions - Race between status check and update - Orphaned process entries in map ### 4.3 Connection State Management **Issues:** - State transitions not atomic - Missing state validation before operations - Concurrent state changes from multiple sources ## 5. Test Coverage Gaps ### 5.1 Critical Paths Without Tests 1. **Concurrent Operations** - Simultaneous process starts/stops - Concurrent log additions under load - Parallel MCP client connections 2. **Error Recovery** - Network failure recovery - Process crash recovery - Configuration corruption recovery 3. **Edge Case Inputs** - Extremely long log lines - Invalid UTF-8 in logs - Malformed URLs - Regex denial of service 4. **Resource Exhaustion** - Channel buffer overflow - Memory limit reached - File descriptor exhaustion - Port exhaustion ### 5.2 Missing Integration Tests 1. **Full lifecycle tests** - Start multiple processes → generate logs → detect errors → stop all - MCP client connection → subscription → updates → disconnection 2. **Stress tests** - High log volume processing - Many concurrent MCP clients - Rapid process start/stop cycles 3. **Platform-specific tests** - Windows process management - WSL-specific behaviors - Signal handling differences ## 6. Recommendations ### 6.1 Immediate Fixes 1. **Add Unsubscribe method to EventBus** ```go func (eb *EventBus) Unsubscribe(eventType EventType, handler Handler) { eb.mu.Lock() defer eb.mu.Unlock() // Implementation needed } ``` 2. **Add timeouts to all channel operations** ```go select { case ch <- data: // Success case <-time.After(timeout): return ErrTimeout } ``` 3. **Implement panic recovery in all goroutines** ```go defer func() { if r := recover(); r != nil { log.Printf("Panic recovered: %v", r) } }() ``` ### 6.2 Testing Improvements 1. **Add race detector tests** ```bash go test -race ./... ``` 2. **Implement chaos testing** - Random process kills - Network interruptions - Resource constraints 3. **Add benchmark tests for critical paths** - Log processing throughput - Event bus performance - Concurrent process management ### 6.3 Monitoring and Debugging 1. **Add goroutine leak detection** 2. **Implement deadlock detection** (already started in pkg/deadlock) 3. **Add metrics for resource usage** 4. **Implement trace logging for debugging** ## 7. Priority Matrix | Issue | Severity | Likelihood | Priority | |-------|----------|------------|----------| | EventBus race conditions | High | High | P0 | | Goroutine leaks | High | Medium | P0 | | Missing Unsubscribe | Medium | High | P1 | | Channel deadlocks | High | Low | P1 | | Process cleanup races | Medium | Medium | P1 | | Network timeout handling | Medium | Medium | P2 | | Memory leaks in maps | Low | Medium | P2 | | Platform-specific issues | Low | Low | P3 | ## 8. Test Implementation Priority 1. **Phase 1: Core Concurrency Tests** - EventBus concurrent operations - LogStore race conditions - Process manager lifecycle 2. **Phase 2: Resource Management Tests** - Goroutine leak detection - Memory usage under load - File handle management 3. **Phase 3: Integration Tests** - Full application lifecycle - Multi-component interactions - Platform-specific behaviors 4. **Phase 4: Chaos and Stress Tests** - Random failure injection - Resource exhaustion scenarios - Performance benchmarks ## Conclusion The Brummer application shows good architectural patterns but needs attention to concurrent access patterns, error handling, and test coverage. The channel-based designs in ConnectionManager are exemplary, while the EventBus needs race condition fixes. Priority should be given to fixing the EventBus races and implementing comprehensive concurrent operation tests.