feat: fix file change(rename) line loss and duplication

tail.go

@@ -2,11 +2,11 @@
 // Copyright (c) 2015 HPE Software Inc. All rights reserved.
 // Copyright (c) 2013 ActiveState Software Inc. All rights reserved.
 
-//nxadm/tail provides a Go library that emulates the features of the BSD `tail`
-//program. The library comes with full support for truncation/move detection as
-//it is designed to work with log rotation tools. The library works on all
-//operating systems supported by Go, including POSIX systems like Linux and
-//*BSD, and MS Windows. Go 1.9 is the oldest compiler release supported.
+// nxadm/tail provides a Go library that emulates the features of the BSD `tail`
+// program. The library comes with full support for truncation/move detection as
+// it is designed to work with log rotation tools. The library works on all
+// operating systems supported by Go, including POSIX systems like Linux and
+// *BSD, and MS Windows. Go 1.9 is the oldest compiler release supported.
 package tail
 
 import (
@@ -21,10 +21,11 @@ import (
 	"sync"
 	"time"
 
+	"gopkg.in/tomb.v1"
+
 	"github.com/nxadm/tail/ratelimiter"
 	"github.com/nxadm/tail/util"
 	"github.com/nxadm/tail/watch"
-	"gopkg.in/tomb.v1"
 )
 
 var (
@@ -383,6 +384,13 @@ func (tail *Tail) waitForChanges() error {
 		}
 	}
 
+	// The write event should be handled first
+	select {
+	case <-tail.changes.Modified:
+		return nil
+	default:
+	}
+
 	select {
 	case <-tail.changes.Modified:
 		return nil

watch/inotify.go

@@ -8,21 +8,24 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"syscall"
 
 	"github.com/nxadm/tail/util"
 
-    "github.com/fsnotify/fsnotify"
+	"github.com/fsnotify/fsnotify"
 	"gopkg.in/tomb.v1"
 )
 
 // InotifyFileWatcher uses inotify to monitor file changes.
 type InotifyFileWatcher struct {
 	Filename string
 	Size     int64
+	// inodeId record cur watch file id
+	inodeId uint64
 }
 
 func NewInotifyFileWatcher(filename string) *InotifyFileWatcher {
-	fw := &InotifyFileWatcher{filepath.Clean(filename), 0}
+	fw := &InotifyFileWatcher{filepath.Clean(filename), 0, 0}
 	return fw
 }
 
@@ -74,6 +77,12 @@ func (fw *InotifyFileWatcher) ChangeEvents(t *tomb.Tomb, pos int64) (*FileChange
 
 	changes := NewFileChanges()
 	fw.Size = pos
+	var stat syscall.Stat_t
+	// record file inodeId
+	err = syscall.Stat(fw.Filename, &stat)
+	if err == nil {
+		fw.inodeId = stat.Ino
+	}
 
 	go func() {
 
@@ -122,10 +131,21 @@ func (fw *InotifyFileWatcher) ChangeEvents(t *tomb.Tomb, pos int64) (*FileChange
 				}
 				fw.Size = fi.Size()
 
+				// No matter what, it is necessary to notify a write event.
+				changes.NotifyModified()
+
 				if prevSize > 0 && prevSize > fw.Size {
+					// file change; if file inodeId changed, notify delete event
+					if fw.inodeId > 0 && fi.Sys() != nil {
+						if statT, fok := fi.Sys().(*syscall.Stat_t); fok {
+							if statT.Ino != fw.inodeId {
+								RemoveWatch(fw.Filename)
+								changes.NotifyDeleted()
+								return
+							}
+						}
+					}
 					changes.NotifyTruncated()
-				} else {
-					changes.NotifyModified()
 				}
 				prevSize = fw.Size
 			}