add log position tracking

local/utl/tracking/log_tailer.go

@@ -11,6 +11,7 @@ type LogTailer struct {
 	handleLine  func(string)
 	stopChan    chan struct{}
 	isRunning   bool
+	tracker     *PositionTracker
 }
 
 func NewLogTailer(filePath string, handleLine func(string)) *LogTailer {
@@ -18,6 +19,7 @@ func NewLogTailer(filePath string, handleLine func(string)) *LogTailer {
 		filePath:   filePath,
 		handleLine: handleLine,
 		stopChan:   make(chan struct{}),
+		tracker:    NewPositionTracker(filePath),
 	}
 }
 
@@ -28,7 +30,13 @@ func (t *LogTailer) Start() {
 	t.isRunning = true
 
 	go func() {
-		var lastSize int64 = 0
+		// Load last position from tracker
+		pos, err := t.tracker.LoadPosition()
+		if err != nil {
+			pos = &LogPosition{} // Start from beginning if error
+		}
+		lastSize := pos.LastPosition
+
 		for {
 			select {
 			case <-t.stopChan:
@@ -56,8 +64,15 @@ func (t *LogTailer) Start() {
 
 					scanner := bufio.NewScanner(file)
 					for scanner.Scan() {
-						t.handleLine(scanner.Text())
+						line := scanner.Text()
+						t.handleLine(line)
 						lastSize, _ = file.Seek(0, 1) // Get current position
+						
+						// Save position periodically
+						t.tracker.SavePosition(&LogPosition{
+							LastPosition: lastSize,
+							LastRead:     line,
+						})
 					}
 
 					file.Close()

local/utl/tracking/position_tracker.go

@@ -0,0 +1,54 @@
+package tracking
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+)
+
+type LogPosition struct {
+	LastPosition int64    `json:"last_position"`
+	LastRead     string   `json:"last_read"`
+}
+
+type PositionTracker struct {
+	positionFile string
+}
+
+func NewPositionTracker(logPath string) *PositionTracker {
+	// Create position file in same directory as log file
+	dir := filepath.Dir(logPath)
+	base := filepath.Base(logPath)
+	positionFile := filepath.Join(dir, "."+base+".position")
+	
+	return &PositionTracker{
+		positionFile: positionFile,
+	}
+}
+
+func (t *PositionTracker) LoadPosition() (*LogPosition, error) {
+	data, err := os.ReadFile(t.positionFile)
+	if err != nil {
+		if os.IsNotExist(err) {
+			// Return empty position if file doesn't exist
+			return &LogPosition{}, nil
+		}
+		return nil, err
+	}
+
+	var pos LogPosition
+	if err := json.Unmarshal(data, &pos); err != nil {
+		return nil, err
+	}
+
+	return &pos, nil
+}
+
+func (t *PositionTracker) SavePosition(pos *LogPosition) error {
+	data, err := json.Marshal(pos)
+	if err != nil {
+		return err
+	}
+
+	return os.WriteFile(t.positionFile, data, 0644)
+}