.gitignore

@@ -1,4 +1,5 @@
 .claude/
+.kvs/
 data/
 data*/
 *.yaml

daemon/daemonize.go

@@ -0,0 +1,87 @@
+package daemon
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"syscall"
+)
+
+// GetLogFilePath returns the log file path for a given config file
+func GetLogFilePath(configPath string) (string, error) {
+	logDir, err := getLogDir()
+	if err != nil {
+		return "", err
+	}
+
+	absConfigPath, err := filepath.Abs(configPath)
+	if err != nil {
+		return "", fmt.Errorf("failed to get absolute config path: %w", err)
+	}
+
+	basename := filepath.Base(configPath)
+	name := filepath.Base(filepath.Dir(absConfigPath)) + "_" + basename
+	return filepath.Join(logDir, name+".log"), nil
+}
+
+// Daemonize spawns the process as a daemon and returns
+func Daemonize(configPath string) error {
+	// Get absolute path to the current executable
+	executable, err := os.Executable()
+	if err != nil {
+		return fmt.Errorf("failed to get executable path: %w", err)
+	}
+
+	// Get absolute path to config
+	absConfigPath, err := filepath.Abs(configPath)
+	if err != nil {
+		return fmt.Errorf("failed to get absolute config path: %w", err)
+	}
+
+	// Check if already running
+	_, running, err := ReadPID(configPath)
+	if err != nil {
+		return fmt.Errorf("failed to check if instance is running: %w", err)
+	}
+	if running {
+		return fmt.Errorf("instance is already running")
+	}
+
+	// Spawn the process in background with --daemon flag
+	cmd := exec.Command(executable, "--daemon", absConfigPath)
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Setsid: true, // Create new session
+	}
+
+	// Redirect stdout/stderr to log file
+	logDir, err := getLogDir()
+	if err != nil {
+		return fmt.Errorf("failed to get log directory: %w", err)
+	}
+	if err := os.MkdirAll(logDir, 0755); err != nil {
+		return fmt.Errorf("failed to create log directory: %w", err)
+	}
+
+	basename := filepath.Base(configPath)
+	name := filepath.Base(filepath.Dir(absConfigPath)) + "_" + basename
+	logFile := filepath.Join(logDir, name+".log")
+
+	f, err := os.OpenFile(logFile, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+	if err != nil {
+		return fmt.Errorf("failed to open log file: %w", err)
+	}
+	defer f.Close()
+
+	cmd.Stdout = f
+	cmd.Stderr = f
+
+	if err := cmd.Start(); err != nil {
+		return fmt.Errorf("failed to start daemon: %w", err)
+	}
+
+	fmt.Printf("Started KVS instance '%s' (PID will be written by daemon)\n", filepath.Base(configPath))
+	fmt.Printf("Logs: %s\n", logFile)
+
+	return nil
+}

daemon/pid.go

@@ -0,0 +1,171 @@
+package daemon
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+// getPIDDir returns the absolute path to the PID directory
+func getPIDDir() (string, error) {
+	homeDir, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("failed to get user home directory: %w", err)
+	}
+	return filepath.Join(homeDir, ".kvs", "pids"), nil
+}
+
+// getLogDir returns the absolute path to the log directory
+func getLogDir() (string, error) {
+	homeDir, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("failed to get user home directory: %w", err)
+	}
+	return filepath.Join(homeDir, ".kvs", "logs"), nil
+}
+
+// GetPIDFilePath returns the PID file path for a given config file
+func GetPIDFilePath(configPath string) string {
+	pidDir, err := getPIDDir()
+	if err != nil {
+		// Fallback to local directory
+		pidDir = ".kvs/pids"
+	}
+
+	// Extract basename without extension
+	basename := filepath.Base(configPath)
+	name := strings.TrimSuffix(basename, filepath.Ext(basename))
+
+	return filepath.Join(pidDir, name+".pid")
+}
+
+// EnsurePIDDir creates the PID directory if it doesn't exist
+func EnsurePIDDir() error {
+	pidDir, err := getPIDDir()
+	if err != nil {
+		return err
+	}
+	return os.MkdirAll(pidDir, 0755)
+}
+
+// WritePID writes the current process PID to a file
+func WritePID(configPath string) error {
+	if err := EnsurePIDDir(); err != nil {
+		return fmt.Errorf("failed to create PID directory: %w", err)
+	}
+
+	pidFile := GetPIDFilePath(configPath)
+	pid := os.Getpid()
+
+	return os.WriteFile(pidFile, []byte(fmt.Sprintf("%d\n", pid)), 0644)
+}
+
+// ReadPID reads the PID from a file and checks if the process is running
+func ReadPID(configPath string) (int, bool, error) {
+	pidFile := GetPIDFilePath(configPath)
+
+	data, err := os.ReadFile(pidFile)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return 0, false, nil
+		}
+		return 0, false, fmt.Errorf("failed to read PID file: %w", err)
+	}
+
+	pidStr := strings.TrimSpace(string(data))
+	pid, err := strconv.Atoi(pidStr)
+	if err != nil {
+		return 0, false, fmt.Errorf("invalid PID in file: %w", err)
+	}
+
+	// Check if process is actually running
+	process, err := os.FindProcess(pid)
+	if err != nil {
+		return pid, false, nil
+	}
+
+	// Send signal 0 to check if process exists
+	err = process.Signal(syscall.Signal(0))
+	if err != nil {
+		return pid, false, nil
+	}
+
+	return pid, true, nil
+}
+
+// RemovePID removes the PID file
+func RemovePID(configPath string) error {
+	pidFile := GetPIDFilePath(configPath)
+	err := os.Remove(pidFile)
+	if err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("failed to remove PID file: %w", err)
+	}
+	return nil
+}
+
+// ListRunningInstances returns a list of running KVS instances
+func ListRunningInstances() ([]InstanceInfo, error) {
+	var instances []InstanceInfo
+
+	pidDir, err := getPIDDir()
+	if err != nil {
+		return nil, err
+	}
+
+	// Check if PID directory exists
+	if _, err := os.Stat(pidDir); os.IsNotExist(err) {
+		return instances, nil
+	}
+
+	entries, err := os.ReadDir(pidDir)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read PID directory: %w", err)
+	}
+
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".pid") {
+			continue
+		}
+
+		name := strings.TrimSuffix(entry.Name(), ".pid")
+		configPath := name + ".yaml" // Assume .yaml extension
+
+		pid, running, err := ReadPID(configPath)
+		if err != nil {
+			continue
+		}
+
+		instances = append(instances, InstanceInfo{
+			Name:    name,
+			PID:     pid,
+			Running: running,
+		})
+	}
+
+	return instances, nil
+}
+
+// InstanceInfo holds information about a KVS instance
+type InstanceInfo struct {
+	Name    string
+	PID     int
+	Running bool
+}
+
+// StopProcess stops a process by PID
+func StopProcess(pid int) error {
+	process, err := os.FindProcess(pid)
+	if err != nil {
+		return fmt.Errorf("failed to find process: %w", err)
+	}
+
+	// Try graceful shutdown first (SIGTERM)
+	if err := process.Signal(syscall.SIGTERM); err != nil {
+		return fmt.Errorf("failed to send SIGTERM: %w", err)
+	}
+
+	return nil
+}

main.go

@@ -6,25 +6,90 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
+	"time"
+
+	"path/filepath"
+	"strings"
 
 	"kvs/config"
+	"kvs/daemon"
 	"kvs/server"
 )
 
 func main() {
-	configPath := "./config.yaml"
-
-	// Simple CLI argument parsing
-	if len(os.Args) > 1 {
-		configPath = os.Args[1]
+	if len(os.Args) < 2 {
+		// No arguments - run in foreground with default config
+		runServer("./config.yaml", false)
+		return
 	}
 
+	// Check if this is a daemon spawn
+	if os.Args[1] == "--daemon" {
+		if len(os.Args) < 3 {
+			fmt.Fprintf(os.Stderr, "Error: --daemon flag requires config path\n")
+			os.Exit(1)
+		}
+		runServer(os.Args[2], true)
+		return
+	}
+
+	// Parse subcommand
+	command := os.Args[1]
+
+	switch command {
+	case "start":
+		if len(os.Args) < 3 {
+			fmt.Fprintf(os.Stderr, "Usage: kvs start <config>\n")
+			os.Exit(1)
+		}
+		cmdStart(normalizeConfigPath(os.Args[2]))
+
+	case "stop":
+		if len(os.Args) < 3 {
+			fmt.Fprintf(os.Stderr, "Usage: kvs stop <config>\n")
+			os.Exit(1)
+		}
+		cmdStop(normalizeConfigPath(os.Args[2]))
+
+	case "restart":
+		if len(os.Args) < 3 {
+			fmt.Fprintf(os.Stderr, "Usage: kvs restart <config>\n")
+			os.Exit(1)
+		}
+		cmdRestart(normalizeConfigPath(os.Args[2]))
+
+	case "status":
+		if len(os.Args) > 2 {
+			cmdStatusSingle(normalizeConfigPath(os.Args[2]))
+		} else {
+			cmdStatusAll()
+		}
+
+	case "help", "--help", "-h":
+		printHelp()
+
+	default:
+		// Backward compatibility: assume it's a config file path
+		runServer(command, false)
+	}
+}
+
+func runServer(configPath string, isDaemon bool) {
 	cfg, err := config.Load(configPath)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to load configuration: %v\n", err)
 		os.Exit(1)
 	}
 
+	// Write PID file if running as daemon
+	if isDaemon {
+		if err := daemon.WritePID(configPath); err != nil {
+			fmt.Fprintf(os.Stderr, "Failed to write PID file: %v\n", err)
+			os.Exit(1)
+		}
+		defer daemon.RemovePID(configPath)
+	}
+
 	kvServer, err := server.NewServer(cfg)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to create server: %v\n", err)
@@ -45,3 +110,135 @@ func main() {
 		os.Exit(1)
 	}
 }
+
+func cmdStart(configPath string) {
+	if err := daemon.Daemonize(configPath); err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to start: %v\n", err)
+		os.Exit(1)
+	}
+}
+
+func cmdStop(configPath string) {
+	pid, running, err := daemon.ReadPID(configPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to read PID: %v\n", err)
+		os.Exit(1)
+	}
+
+	if !running {
+		fmt.Printf("Instance '%s' is not running\n", configPath)
+		// Clean up stale PID file
+		daemon.RemovePID(configPath)
+		return
+	}
+
+	fmt.Printf("Stopping instance '%s' (PID %d)...\n", configPath, pid)
+	if err := daemon.StopProcess(pid); err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to stop process: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Wait a bit and verify it stopped
+	time.Sleep(1 * time.Second)
+	_, stillRunning, _ := daemon.ReadPID(configPath)
+	if stillRunning {
+		fmt.Printf("Warning: Process may still be running\n")
+	} else {
+		daemon.RemovePID(configPath)
+		fmt.Printf("Stopped successfully\n")
+	}
+}
+
+func cmdRestart(configPath string) {
+	// Check if running
+	_, running, err := daemon.ReadPID(configPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to check status: %v\n", err)
+		os.Exit(1)
+	}
+
+	if running {
+		cmdStop(configPath)
+		// Wait a bit for clean shutdown
+		time.Sleep(2 * time.Second)
+	}
+
+	cmdStart(configPath)
+}
+
+func cmdStatusSingle(configPath string) {
+	pid, running, err := daemon.ReadPID(configPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to read PID: %v\n", err)
+		os.Exit(1)
+	}
+
+	if running {
+		fmt.Printf("Instance '%s': RUNNING (PID %d)\n", configPath, pid)
+	} else if pid > 0 {
+		fmt.Printf("Instance '%s': STOPPED (stale PID %d)\n", configPath, pid)
+	} else {
+		fmt.Printf("Instance '%s': STOPPED\n", configPath)
+	}
+}
+
+func cmdStatusAll() {
+	instances, err := daemon.ListRunningInstances()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to list instances: %v\n", err)
+		os.Exit(1)
+	}
+
+	if len(instances) == 0 {
+		fmt.Println("No KVS instances found")
+		return
+	}
+
+	fmt.Println("KVS Instances:")
+	for _, inst := range instances {
+		status := "STOPPED"
+		if inst.Running {
+			status = "RUNNING"
+		}
+		fmt.Printf("  %-20s %s (PID %d)\n", inst.Name, status, inst.PID)
+	}
+}
+
+// normalizeConfigPath ensures config path has .yaml extension if not specified
+func normalizeConfigPath(path string) string {
+	// If path doesn't have an extension, add .yaml
+	if filepath.Ext(path) == "" {
+		return path + ".yaml"
+	}
+	return path
+}
+
+// getConfigIdentifier returns the identifier for a config (basename without extension)
+// This is used for PID files and status display
+func getConfigIdentifier(path string) string {
+	basename := filepath.Base(path)
+	return strings.TrimSuffix(basename, filepath.Ext(basename))
+}
+
+func printHelp() {
+	help := `KVS - Distributed Key-Value Store
+
+Usage:
+  kvs [config.yaml]              Run in foreground (default: ./config.yaml)
+  kvs start <config>             Start as daemon (.yaml extension optional)
+  kvs stop <config>              Stop daemon (.yaml extension optional)
+  kvs restart <config>           Restart daemon (.yaml extension optional)
+  kvs status [config]            Show status (all instances if no config given)
+  kvs help                       Show this help
+
+Examples:
+  kvs                            # Run with ./config.yaml in foreground
+  kvs node1.yaml                 # Run with node1.yaml in foreground
+  kvs start node1                # Start node1.yaml as daemon
+  kvs start node1.yaml           # Same as above
+  kvs stop node1                 # Stop node1 daemon
+  kvs status                     # Show all running instances
+  kvs status node1               # Show status of node1
+`
+	fmt.Print(help)
+}