fix: for long chunks provide max buffer size configuration

pkg/flags.go

@@ -21,6 +21,7 @@ type Flags struct {
 	MemLimit         int
 	MSTeamsHook      string
 	NotifyOnlyRecent bool
+	MaxBufferSizeMB  int
 	Test             bool
 	Version          bool
 }
@@ -41,6 +42,7 @@ sends health check ping to ms teams webhook
 	flag.IntVar(&f.MemLimit, "mem-limit", 256, "memory limit in MB (0 to disable)")
 	flag.IntVar(&f.FilePathsCap, "file-paths-cap", 100, "max number of file paths to watch")
 	flag.IntVar(&f.Min, "min", 1, "on minimum num of matches, it should notify")
+	flag.IntVar(&f.MaxBufferSizeMB, "max-buffer-size-mb", 0, "max buffer size in MB, default is 0 (not provided) for go's default 64KB")
 	flag.BoolVar(&f.NotifyOnlyRecent, "notify-only-recent", true, "Notify on latest file only by timestamp based on --every")
 	flag.BoolVar(&f.Version, "version", false, "")
 	flag.BoolVar(&f.Test, "test", false, `Quickly test paths or regex

pkg/watcher.go

@@ -18,6 +18,7 @@ type Watcher struct {
 	lastFileSizeKey string
 	matchPattern    string
 	ignorePattern   string
+	maxBufferSizeMB int
 	lastLineNum     int
 	lastFileSize    int64
 	timestampNow    string
@@ -43,6 +44,7 @@ func NewWatcher(
 		lastLineKey:     "llk-" + filePath,
 		lastFileSizeKey: "llks-" + filePath,
 		timestampNow:    now.Format("2006-01-02 15:04:05"),
+		maxBufferSizeMB: f.MaxBufferSizeMB,
 	}
 	if err := watcher.loadState(); err != nil {
 		return nil, err
@@ -102,6 +104,10 @@ func (w *Watcher) Scan() (*ScanResult, error) {
 	}
 
 	scanner := bufio.NewScanner(file)
+	if w.maxBufferSizeMB > 0 {
+		// for large lines
+		scanner.Buffer(make([]byte, 0, 64*1024), w.maxBufferSizeMB*1024*1024)
+	}
 	currentLineNum := 1
 	linesRead := 0
 	bytesRead := w.lastFileSize