feat: automatic swap file management for OOM prevention during large backups

internal/backup/engine.go

@@ -18,6 +18,7 @@ import (
 	"dbbackup/internal/database"
 	"dbbackup/internal/logger"
 	"dbbackup/internal/progress"
+	"dbbackup/internal/swap"
 )
 
 // Engine handles backup operations
@@ -252,6 +253,31 @@ func (e *Engine) BackupCluster(ctx context.Context) error {
 	
 	operation := e.log.StartOperation("Cluster Backup")
 	
+	// Setup swap file if configured
+	var swapMgr *swap.Manager
+	if e.cfg.AutoSwap && e.cfg.SwapFileSizeGB > 0 {
+		swapMgr = swap.NewManager(e.cfg.SwapFilePath, e.cfg.SwapFileSizeGB, e.log)
+		
+		if swapMgr.IsSupported() {
+			e.log.Info("Setting up temporary swap file for large backup", 
+				"path", e.cfg.SwapFilePath, 
+				"size_gb", e.cfg.SwapFileSizeGB)
+			
+			if err := swapMgr.Setup(); err != nil {
+				e.log.Warn("Failed to setup swap file (continuing without it)", "error", err)
+			} else {
+				// Ensure cleanup on exit
+				defer func() {
+					if err := swapMgr.Cleanup(); err != nil {
+						e.log.Warn("Failed to cleanup swap file", "error", err)
+					}
+				}()
+			}
+		} else {
+			e.log.Warn("Swap file management not supported on this platform", "os", swapMgr)
+		}
+	}
+	
 	// Use a quiet progress indicator to avoid duplicate messages
 	quietProgress := progress.NewQuietLineByLine()
 	quietProgress.Start("Starting cluster backup (all databases)")

internal/config/config.go

@@ -56,6 +56,11 @@ type Config struct {
 	RestoreDBName string
 	// Timeouts (in minutes)
 	ClusterTimeoutMinutes int
+
+	// Swap file management (for large backups)
+	SwapFilePath   string // Path to temporary swap file
+	SwapFileSizeGB int    // Size in GB (0 = disabled)
+	AutoSwap       bool   // Automatically manage swap for large backups
 }
 
 // New creates a new configuration with default values
@@ -134,6 +139,11 @@ func New() *Config {
 
 		// Timeouts
 		ClusterTimeoutMinutes: getEnvInt("CLUSTER_TIMEOUT_MIN", 240),
+
+		// Swap file management
+		SwapFilePath:   getEnvString("SWAP_FILE_PATH", "/tmp/dbbackup_swap"),
+		SwapFileSizeGB: getEnvInt("SWAP_FILE_SIZE_GB", 0), // 0 = disabled by default
+		AutoSwap:       getEnvBool("AUTO_SWAP", false),
 	}
 
 	// Ensure canonical defaults are enforced

internal/swap/swap.go

@@ -0,0 +1,233 @@
+package swap
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+
+	"dbbackup/internal/logger"
+)
+
+// Manager handles temporary swap file creation and cleanup
+type Manager struct {
+	swapPath   string
+	sizeGB     int
+	isActive   bool
+	wasCreated bool
+	log        logger.Logger
+}
+
+// NewManager creates a new swap file manager
+func NewManager(swapPath string, sizeGB int, log logger.Logger) *Manager {
+	return &Manager{
+		swapPath: swapPath,
+		sizeGB:   sizeGB,
+		log:      log,
+	}
+}
+
+// IsSupported checks if swap file management is supported on this platform
+func (m *Manager) IsSupported() bool {
+	// Only supported on Linux
+	return runtime.GOOS == "linux"
+}
+
+// NeedsRoot checks if we need root privileges for swap operations
+func (m *Manager) NeedsRoot() bool {
+	// On Linux, swap operations require root
+	return runtime.GOOS == "linux" && os.Geteuid() != 0
+}
+
+// GetCurrentSwap returns current swap usage info
+func (m *Manager) GetCurrentSwap() (totalMB, usedMB, freeMB int64, err error) {
+	// Read /proc/meminfo for swap info
+	data, err := os.ReadFile("/proc/meminfo")
+	if err != nil {
+		return 0, 0, 0, err
+	}
+
+	lines := strings.Split(string(data), "\n")
+	for _, line := range lines {
+		fields := strings.Fields(line)
+		if len(fields) < 2 {
+			continue
+		}
+
+		switch fields[0] {
+		case "SwapTotal:":
+			if val, err := strconv.ParseInt(fields[1], 10, 64); err == nil {
+				totalMB = val / 1024
+			}
+		case "SwapFree:":
+			if val, err := strconv.ParseInt(fields[1], 10, 64); err == nil {
+				freeMB = val / 1024
+			}
+		}
+	}
+	usedMB = totalMB - freeMB
+	return
+}
+
+// IsSwapFileActive checks if our specific swap file is currently active
+func (m *Manager) IsSwapFileActive() (bool, error) {
+	// Read /proc/swaps to see active swap devices
+	data, err := os.ReadFile("/proc/swaps")
+	if err != nil {
+		return false, err
+	}
+
+	absPath, _ := filepath.Abs(m.swapPath)
+	lines := strings.Split(string(data), "\n")
+	for _, line := range lines {
+		if strings.Contains(line, absPath) || strings.Contains(line, m.swapPath) {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// Setup creates and enables the swap file if needed
+func (m *Manager) Setup() error {
+	if !m.IsSupported() {
+		return fmt.Errorf("swap file management not supported on %s", runtime.GOOS)
+	}
+
+	if m.sizeGB <= 0 {
+		return fmt.Errorf("swap size must be > 0 GB")
+	}
+
+	if m.NeedsRoot() {
+		m.log.Warn("Swap file creation requires root privileges, skipping automatic swap setup")
+		return fmt.Errorf("swap file operations require root privileges (current euid: %d)", os.Geteuid())
+	}
+
+	m.log.Info("Setting up temporary swap file", "path", m.swapPath, "size_gb", m.sizeGB)
+
+	// Check if swap file already exists and is active
+	if active, _ := m.IsSwapFileActive(); active {
+		m.log.Info("Swap file already active", "path", m.swapPath)
+		m.isActive = true
+		return nil
+	}
+
+	// Check if file exists but is not active
+	if _, err := os.Stat(m.swapPath); err == nil {
+		m.log.Warn("Swap file exists but is not active, removing", "path", m.swapPath)
+		if err := os.Remove(m.swapPath); err != nil {
+			return fmt.Errorf("failed to remove existing swap file: %w", err)
+		}
+	}
+
+	// Create swap file directory if needed
+	swapDir := filepath.Dir(m.swapPath)
+	if err := os.MkdirAll(swapDir, 0755); err != nil {
+		return fmt.Errorf("failed to create swap directory: %w", err)
+	}
+
+	// Calculate size in bytes
+	sizeBytes := int64(m.sizeGB) * 1024 * 1024 * 1024
+
+	m.log.Info("Creating swap file", "size_bytes", sizeBytes)
+
+	// Use fallocate for fast file creation
+	cmd := exec.Command("fallocate", "-l", fmt.Sprintf("%d", sizeBytes), m.swapPath)
+	if output, err := cmd.CombinedOutput(); err != nil {
+		// Fallback to dd if fallocate fails
+		m.log.Warn("fallocate failed, using dd (slower)", "error", err, "output", string(output))
+		cmd = exec.Command("dd", "if=/dev/zero", "of="+m.swapPath, "bs=1M", fmt.Sprintf("count=%d", m.sizeGB*1024))
+		if output, err := cmd.CombinedOutput(); err != nil {
+			return fmt.Errorf("failed to create swap file with dd: %w (output: %s)", err, string(output))
+		}
+	}
+	m.wasCreated = true
+
+	// Set correct permissions (600 for security)
+	if err := os.Chmod(m.swapPath, 0600); err != nil {
+		m.cleanup()
+		return fmt.Errorf("failed to set swap file permissions: %w", err)
+	}
+
+	// Format as swap
+	m.log.Info("Formatting swap file")
+	cmd = exec.Command("mkswap", m.swapPath)
+	if output, err := cmd.CombinedOutput(); err != nil {
+		m.cleanup()
+		return fmt.Errorf("failed to format swap file: %w (output: %s)", err, string(output))
+	}
+
+	// Enable swap
+	m.log.Info("Enabling swap file")
+	cmd = exec.Command("swapon", m.swapPath)
+	if output, err := cmd.CombinedOutput(); err != nil {
+		m.cleanup()
+		return fmt.Errorf("failed to enable swap file: %w (output: %s)", err, string(output))
+	}
+
+	m.isActive = true
+
+	// Log current swap status
+	if total, used, free, err := m.GetCurrentSwap(); err == nil {
+		m.log.Info("Swap status after setup", 
+			"total_mb", total, 
+			"used_mb", used, 
+			"free_mb", free,
+			"added_gb", m.sizeGB)
+	}
+
+	return nil
+}
+
+// cleanup removes the swap file (internal helper)
+func (m *Manager) cleanup() {
+	if m.wasCreated {
+		os.Remove(m.swapPath)
+		m.wasCreated = false
+	}
+}
+
+// Cleanup disables and removes the swap file
+func (m *Manager) Cleanup() error {
+	if !m.isActive {
+		return nil
+	}
+
+	m.log.Info("Cleaning up swap file", "path", m.swapPath)
+
+	// Check if still active
+	if active, _ := m.IsSwapFileActive(); active {
+		// Disable swap
+		m.log.Info("Disabling swap file")
+		cmd := exec.Command("swapoff", m.swapPath)
+		if output, err := cmd.CombinedOutput(); err != nil {
+			m.log.Warn("Failed to disable swap file", "error", err, "output", string(output))
+			// Continue anyway
+		}
+	}
+
+	// Remove file if we created it
+	if m.wasCreated {
+		m.log.Info("Removing swap file", "path", m.swapPath)
+		if err := os.Remove(m.swapPath); err != nil {
+			m.log.Warn("Failed to remove swap file", "error", err)
+			return fmt.Errorf("failed to remove swap file: %w", err)
+		}
+		m.wasCreated = false
+	}
+
+	m.isActive = false
+	return nil
+}
+
+// IsActive returns whether the swap file is currently active
+func (m *Manager) IsActive() bool {
+	return m.isActive
+}
+
+// WasCreated returns whether this manager created the swap file
+func (m *Manager) WasCreated() bool {
+	return m.wasCreated
+}