Added all of the existing code

2025-09-27 14:43:52 +01:00
commit 6772bfd842
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--- a/FREEZING_ISSUE_FIXES.md
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+# TechIRCd Freezing Issue - Fixes Applied
+
+## Issue Description
+TechIRCd was experiencing freezing/hanging issues where the server would become unresponsive after running for a while, preventing new user connections and causing existing users to disconnect.
+
+## Root Causes Identified
+
+### 1. Resource Leaks in Client Handling
+- **Problem**: Disconnected clients weren't being properly cleaned up, leading to memory leaks and resource exhaustion
+- **Symptoms**: Server gradually becoming slower and eventually unresponsive
+
+### 2. Goroutine Leaks
+- **Problem**: Client handler goroutines weren't exiting properly when connections were broken
+- **Symptoms**: Increasing number of goroutines over time, eventually exhausting system resources
+
+### 3. Lock Contention in Ping/Health Checks
+- **Problem**: Server-wide ping and health checks were holding locks too long and running synchronously
+- **Symptoms**: Server becoming unresponsive during health checks, client operations timing out
+
+### 4. Inefficient Connection State Management
+- **Problem**: Inconsistent tracking of client connection state, leading to operations on dead connections
+- **Symptoms**: Hanging writes, blocked goroutines, server freezing
+
+### 5. Deadlocked Shutdown Process
+- **Problem**: Shutdown process could deadlock when trying to notify clients while holding locks
+- **Symptoms**: Ctrl+C not working, server becoming completely unresponsive, requiring SIGKILL
+
+## Fixes Applied
+
+### 1. Enhanced Client Cleanup (`client.go`)
+
+#### Before:
+```go
+func (c *Client) cleanup() {
+    // Basic cleanup with potential blocking operations
+    if c.conn != nil {
+        c.conn.Close()  // Could hang
+    }
+    // Synchronous channel cleanup
+    // Synchronous server removal
+}
+```
+
+#### After:
+```go
+func (c *Client) cleanup() {
+    // Non-blocking cleanup with timeouts
+    if c.conn != nil {
+        c.conn.SetDeadline(time.Now().Add(5 * time.Second))
+        c.conn.Close()
+    }
+    // Asynchronous channel cleanup in goroutine
+    // Asynchronous server removal in goroutine
+}
+```
+
+**Benefits:**
+- Prevents cleanup operations from blocking other clients
+- Uses timeouts to force close hanging connections
+- Prevents deadlocks during shutdown
+
+### 2. Improved Connection Handling
+
+#### Connection Timeout Management:
+```go
+func (c *Client) handleMessageRead(...) bool {
+    // Set read deadline with timeout to prevent hanging
+    readTimeout := 30 * time.Second
+    if c.IsRegistered() {
+        readTimeout = 5 * time.Minute
+    }
+    
+    // Use goroutine with timeout for non-blocking reads
+    scanChan := make(chan bool, 1)
+    go func() {
+        // Scanner in separate goroutine
+        scanChan <- scanner.Scan()
+    }()
+    
+    select {
+    case result := <-scanChan:
+        // Process result
+    case <-time.After(readTimeout):
+        // Handle timeout
+        return false
+    }
+}
+```
+
+**Benefits:**
+- Prevents infinite blocking on read operations
+- Detects and handles dead connections quickly
+- Provides graceful timeout handling
+
+### 3. Non-blocking Ping and Health Checks (`server.go`)
+
+#### Before:
+```go
+func (s *Server) pingRoutine() {
+    ticker := time.NewTicker(30 * time.Second)
+    for {
+        select {
+        case <-ticker.C:
+            s.performPingCheck()  // Blocking operation
+        }
+    }
+}
+```
+
+#### After:
+```go
+func (s *Server) pingRoutine() {
+    ticker := time.NewTicker(60 * time.Second)  // Less frequent
+    for {
+        select {
+        case <-ticker.C:
+            go s.performPingCheck()  // Non-blocking
+        }
+    }
+}
+```
+
+#### Enhanced Ping Check:
+```go
+func (s *Server) performPingCheck() {
+    // Get snapshot of client IDs without holding lock
+    s.mu.RLock()
+    clientIDs := make([]string, 0, len(s.clients))
+    for clientID := range s.clients {
+        clientIDs = append(clientIDs, clientID)
+    }
+    s.mu.RUnlock()
+    
+    // Process clients individually to prevent blocking
+    for _, clientID := range clientIDs {
+        // Non-blocking ping sending
+        go func(id string) {
+            // Send ping in separate goroutine
+        }(clientID)
+    }
+}
+```
+
+**Benefits:**
+- Eliminates blocking during server-wide operations
+- Reduces lock contention
+- Prevents cascade failures
+
+### 4. Batched Health Checks
+
+#### Before:
+```go
+func (s *Server) performHealthCheck() {
+    // Hold lock for entire operation
+    s.mu.RLock()
+    clients := make([]*Client, 0, len(s.clients))
+    // ... process all clients synchronously
+    s.mu.RUnlock()
+}
+```
+
+#### After:
+```go
+func (s *Server) performHealthCheck() {
+    // Process clients in batches of 50
+    batchSize := 50
+    for i := 0; i < len(clientIDs); i += batchSize {
+        batch := clientIDs[i:end]
+        for _, clientID := range batch {
+            // Process each client individually
+        }
+        // Small delay between batches
+        time.Sleep(10 * time.Millisecond)
+    }
+}
+```
+
+**Benefits:**
+- Prevents overwhelming the system during health checks
+- Allows other operations to proceed between batches
+- Reduces memory usage during large client counts
+
+### 5. Enhanced Error Recovery
+
+#### Panic Recovery:
+```go
+defer func() {
+    if r := recover(); r != nil {
+        log.Printf("Panic in client handler for %s: %v", c.getClientInfo(), r)
+    }
+    c.cleanup()
+}()
+```
+
+#### Graceful Disconnection:
+```go
+func (c *Client) ForceDisconnect(reason string) {
+    log.Printf("Force disconnecting client %s: %s", c.getClientInfo(), reason)
+    
+    c.mu.Lock()
+    c.disconnected = true
+    c.mu.Unlock()
+    
+    if c.conn != nil {
+        c.SendMessage(fmt.Sprintf("ERROR :%s", reason))
+    }
+}
+```
+
+### 5. Robust Shutdown Process (`server.go` & `main.go`)
+
+#### Before:
+```go
+func (s *Server) Shutdown() {
+    // Could deadlock holding locks
+    s.mu.RLock()
+    for _, client := range s.clients {
+        client.SendMessage("ERROR :Server shutting down")
+    }
+    s.mu.RUnlock()
+    close(s.shutdown)
+}
+```
+
+#### After:
+```go
+func (s *Server) Shutdown() {
+    // Non-blocking shutdown with timeout protection
+    
+    // Close listeners immediately
+    go func() { /* close listeners */ }()
+    
+    // Signal shutdown first
+    close(s.shutdown)
+    
+    // Disconnect clients in batches asynchronously
+    go func() {
+        // Process clients in batches of 10
+        // Each client disconnection in separate goroutine
+        // Timeout protection for each operation
+    }()
+    
+    // Force shutdown after reasonable timeout
+    time.Sleep(2 * time.Second)
+}
+```
+
+#### Signal Handling with Force Option:
+```go
+// Double Ctrl+C for immediate shutdown
+if shutdownInProgress {
+    log.Println("Forcing immediate shutdown...")
+    os.Exit(1)
+}
+
+// Timeout protection for graceful shutdown
+select {
+case <-shutdownComplete:
+    log.Println("Graceful shutdown completed")
+case <-time.After(10 * time.Second):
+    log.Println("Shutdown timeout, forcing exit...")
+}
+```
+
+**Benefits:**
+- Prevents deadlocks during shutdown
+- Allows double Ctrl+C for immediate force shutdown
+- Timeout protection prevents hanging shutdown
+- Asynchronous operations prevent blocking
+
+## Configuration Optimizations
+
+### Timing Adjustments:
+- **Ping Interval**: Increased from 30s to 60s to reduce overhead
+- **Health Check Interval**: Increased from 60s to 5 minutes
+- **Read Timeouts**: More conservative timeouts for better stability
+- **Registration Timeout**: Better enforcement to prevent hanging registrations
+
+### Resource Limits:
+- **Batch Processing**: Health checks limited to 50 clients per batch
+- **Connection Limits**: Better enforcement of max client limits
+- **Memory Management**: Proactive cleanup of disconnected clients
+
+## Expected Results
+
+1. **Stability**: Server should remain responsive under normal load
+2. **Resource Usage**: More predictable memory and goroutine usage
+3. **Connection Handling**: Faster detection and cleanup of dead connections
+4. **Performance**: Reduced lock contention and blocking operations
+5. **Monitoring**: Better logging and health monitoring
+
+## Monitoring
+
+The server now provides better logging for:
+- Client connection/disconnection events
+- Health check results and statistics
+- Resource usage patterns
+- Error conditions and recovery actions
+
+## Testing
+
+I've created test scripts to verify the fixes:
+
+### 1. Shutdown Test (`test_shutdown.sh`)
+- Tests graceful shutdown behavior
+- Verifies server responds to SIGTERM
+- Confirms shutdown completes within reasonable time
+
+### 2. Stress Test (`test_stress.sh`)
+- Simulates conditions that previously caused freezing
+- Creates multiple stable and unstable connections
+- Tests rapid connection/disconnection patterns
+- Monitors server responsiveness during stress
+- Verifies shutdown works after stress conditions
+
+### Usage:
+```bash
+# Test shutdown behavior
+./test_shutdown.sh
+
+# Test stability under stress
+./test_stress.sh
+```
+
+## Future Improvements
+
+1. **Metrics Endpoint**: Add HTTP endpoint for real-time metrics
+2. **Connection Pooling**: Implement connection pooling for better resource management
+3. **Circuit Breakers**: Add circuit breakers for failing operations
+4. **Rate Limiting**: Enhanced rate limiting per IP/user