Bugfixes, add INFO command, graceful shutdown. elimitate dead code

- Remove unsed handleClientKill, handleClientKill
- Fix misleading error message on rate limit
- Eliminated unused channel-to-pattern index that was causing unnecessary work
- Fixed O(n²) duplicate check in PublishToPattern
- Limit total pattern subscriptions to 10,000
- Limit channel subscriptions per client to 10,000
- Added INFO command
- Added graceful shutdown timeout
- Validate that log directory is writable during config load
- Make SELECT properly handle whitespace around DB index like Redis
- Return proper error instead of empty array for unsupported commands on sharded pubsub stubs
- More accurate error messages throughout
- Updated README.md

internal/server/server.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"math/rand"
 	"net"
 	"os"
 	"strconv"
@@ -23,21 +24,35 @@ import (
 
 const MaxDatabases = 16 // Redis default maximum databases (0-15)
 
+// generateRunID generates a 40-character hexadecimal run ID like Redis.
+// Redis uses SHA1 of random data for 160 bits of randomness.
+func generateRunID() string {
+	b := make([]byte, 20)
+	_, _ = rand.Read(b)
+	return fmt.Sprintf("%x", b)
+}
+
 // Sentinel errors for connection handling
 var (
 	ErrQuit = errors.New("client quit")
 )
 
+// Version is set at build time via -ldflags
+var Version = "unknown"
+
 // Server is the main Pekoe server instance.
 // It manages the TCP listener, connection lifecycle, and delegates to the pubsub hub.
 type Server struct {
-	cfg    *config.Config
-	hub    pubsubHub
-	ln     net.Listener
-	wg     sync.WaitGroup
-	ctx    context.Context
-	cancel context.CancelFunc
-	active atomic.Int64 // atomic counter for active connections
+	cfg       *config.Config
+	hub       pubsubHub
+	ln        net.Listener
+	wg        sync.WaitGroup
+	ctx       context.Context
+	cancel    context.CancelFunc
+	active    atomic.Int64 // atomic counter for active connections
+	version   string       // server version for INFO command
+	startTime time.Time    // server start time for uptime calculation
+	runID     string       // random run ID
 }
 
 // PubSubHub defines the interface our server expects from the pubsub implementation.
@@ -65,10 +80,13 @@ type pubsubHub interface {
 func New(cfg *config.Config, hub pubsubHub) *Server {
 	ctx, cancel := context.WithCancel(context.Background())
 	return &Server{
-		cfg:    cfg,
-		hub:    hub,
-		ctx:    ctx,
-		cancel: cancel,
+		cfg:       cfg,
+		hub:       hub,
+		ctx:       ctx,
+		cancel:    cancel,
+		version:   Version,
+		startTime: time.Now(),
+		runID:     generateRunID(),
 	}
 }
 
@@ -105,6 +123,11 @@ func (s *Server) Run() error {
 // createPidFile creates the PID file with the current process ID
 func (s *Server) createPidFile() error {
 	pid := strconv.Itoa(os.Getpid())
+	// Remove existing pid file first to handle stale files from previous runs
+	// This also fixes permission denied errors when file already exists
+	if err := os.Remove(s.cfg.PidFile); err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return fmt.Errorf("failed to remove existing pid file: %w", err)
+	}
 	//nolint: gosec
 	return os.WriteFile(s.cfg.PidFile, []byte(pid), 0644)
 }
@@ -280,6 +303,8 @@ func (s *Server) processCommand(client *pubsub.Client, cmd *Command, writer *Con
 		return s.handleClient(client, cmd.Args[1:], writer)
 	case "select":
 		return s.handleSelect(client, cmd.Args[1:], writer)
+	case "info":
+		return s.handleInfo(writer)
 	default:
 		// Check if client is in pubsub mode - only pubsub commands allowed
 		if client != nil && (client.SubsCount() > 0 || client.PatternSubsCount() > 0) {
@@ -315,8 +340,27 @@ func (s *Server) waitForSignal() {
 				logger.Error("event=listener_close_error error=%v", err)
 			}
 
-			// Wait for all active connections to finish
-			s.wg.Wait()
+			// Wait for all active connections to finish with timeout
+			shutdownTimeout := time.Duration(s.cfg.ShutdownTimeout) * time.Second
+			if shutdownTimeout > 0 {
+				// Create a channel to wait on wg.Wait() with timeout
+				done := make(chan struct{})
+				go func() {
+					s.wg.Wait()
+					close(done)
+				}()
+
+				select {
+				case <-done:
+					// All connections finished normally
+				case <-time.After(shutdownTimeout):
+					// Timeout reached - force cleanup
+					logger.Warn("event=shutdown_timeout timeout=%ds active_connections=%d", s.cfg.ShutdownTimeout, s.active.Load())
+				}
+			} else {
+				// No timeout - wait forever (original behavior)
+				s.wg.Wait()
+			}
 
 			// Remove PID file
 			s.removePidFile()