context aware grep with -max -after and -before not work

1 files changed, 61 insertions, 0 deletions

diff --git a/internal/io/fs/truncate.go b/internal/io/fs/truncate.go
new file mode 100644
index 0000000..a8d59ac
--- /dev/null
+++ b/internal/io/fs/truncate.go
@@ -0,0 +1,61 @@
+package fs
+
+import (
+	"context"
+	"errors"
+	"io"
+	"os"
+	"time"
+
+	"github.com/mimecast/dtail/internal/io/logger"
+)
+
+func (f readFile) truncateTimer(ctx context.Context) (checkTruncate chan struct{}) {
+	checkTruncate = make(chan struct{})
+
+	go func() {
+		for {
+			select {
+			case <-time.After(time.Second * 3):
+				select {
+				case checkTruncate <- struct{}{}:
+				case <-ctx.Done():
+				}
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	return
+}
+
+// Check wether log file is truncated. Returns nil if not.
+func (f readFile) truncated(fd *os.File) (bool, error) {
+	logger.Debug(f.filePath, "File truncation check")
+
+	// Can not seek currently open FD.
+	curPos, err := fd.Seek(0, os.SEEK_CUR)
+	if err != nil {
+		return true, err
+	}
+
+	// Can not open file at original path.
+	pathFd, err := os.Open(f.filePath)
+	if err != nil {
+		return true, err
+	}
+	defer pathFd.Close()
+
+	// Can not seek file at original path.
+	pathPos, err := pathFd.Seek(0, io.SeekEnd)
+	if err != nil {
+		return true, err
+	}
+
+	if curPos > pathPos {
+		return true, errors.New("File got truncated")
+	}
+
+	return false, nil
+}