From 2cddd48e0a3479555b5a83373aeea14af405c3fd Mon Sep 17 00:00:00 2001
From: Sridhar Ratnakumar <sridharr@activestate.com>
Date: Wed, 29 May 2013 11:35:27 -0700
Subject: [PATCH] clean up ChangeEvents' goroutines upon tail.Stop

---
 CHANGES.md       |  3 ++-
 tail.go          |  8 ++++----
 watch/inotify.go | 14 ++++++++++----
 watch/polling.go |  8 +++++---
 watch/watch.go   |  2 +-
 5 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index f7579c7..a1654d5 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,9 +1,10 @@
 # May, 2013
 
-* Recognize deletions/renames when using polling file watcher (PR #1)
+* Detect file deletions/renames in polling file watcher (PR #1)
 * Detect file truncation
 * Fix potential race condition when reopening the file (issue 5)
 * Fix potential blocking of `tail.Stop` (issue 4)
+* Fix uncleaned up ChangeEvents goroutines after calling tail.Stop
 
 # Feb, 2013
 
diff --git a/tail.go b/tail.go
index a1cd6d0..9cb2716 100644
--- a/tail.go
+++ b/tail.go
@@ -179,17 +179,17 @@ func (tail *Tail) tailFileSync() {
 						tail.Kill(err)
 						return
 					}
-					changes = tail.watcher.ChangeEvents(st)
+					changes = tail.watcher.ChangeEvents(tail.Tomb, st)
 				}
 
 				select {
 				case _, ok := <-changes:
 					if !ok {
-						changes = nil // XXX: use tomb to kill changes' goroutine.
+						changes = nil
 
 						// File got deleted/renamed/truncated.
 						if tail.ReOpen {
-							// TODO: no logging in a library?
+							// XXX: no logging in a library?
 							log.Printf("Re-opening moved/deleted/truncated file %s ...", tail.Filename)
 							err := tail.reopen()
 							if err != nil {
@@ -202,7 +202,7 @@ func (tail *Tail) tailFileSync() {
 
 							continue
 						} else {
-							log.Printf("Finishing because file has been moved/deleted: %s", tail.Filename)
+							log.Printf("Stopping tail as file no longer exists: %s", tail.Filename)
 							tail.close()
 							return
 						}
diff --git a/watch/inotify.go b/watch/inotify.go
index ba80c57..cb732c0 100644
--- a/watch/inotify.go
+++ b/watch/inotify.go
@@ -3,7 +3,6 @@
 package watch
 
 import (
-	"fmt"
 	"github.com/howeyc/fsnotify"
 	"os"
 	"path/filepath"
@@ -51,14 +50,14 @@ func (fw *InotifyFileWatcher) BlockUntilExists(t tomb.Tomb) error {
 				return nil
 			}
 		case <-t.Dying():
-			return fmt.Errorf("Tomb dying")
+			return tomb.ErrDying
 		}
 	}
 	panic("unreachable")
 }
 
 // ChangeEvents returns a channel that gets updated when the file is ready to be read.
-func (fw *InotifyFileWatcher) ChangeEvents(fi os.FileInfo) chan bool {
+func (fw *InotifyFileWatcher) ChangeEvents(t tomb.Tomb, fi os.FileInfo) chan bool {
 	w, err := fsnotify.NewWatcher()
 	if err != nil {
 		panic(err)
@@ -80,7 +79,14 @@ func (fw *InotifyFileWatcher) ChangeEvents(fi os.FileInfo) chan bool {
 		for {
 			prevSize := fw.Size
 
-			evt := <-w.Event
+			var evt *fsnotify.FileEvent
+
+			select {
+			case evt = <-w.Event:
+			case <-t.Dying():
+				return
+			}
+
 			switch {
 			case evt.IsDelete():
 				fallthrough
diff --git a/watch/polling.go b/watch/polling.go
index 7c694f6..ca1ee62 100644
--- a/watch/polling.go
+++ b/watch/polling.go
@@ -7,7 +7,6 @@ import (
 	"os"
 	"sync"
 	"time"
-	"fmt"
 )
 
 // PollingFileWatcher polls the file for changes.
@@ -34,13 +33,13 @@ func (fw *PollingFileWatcher) BlockUntilExists(t tomb.Tomb) error {
 		case <-time.After(POLL_DURATION):
 			continue
 		case <-t.Dying():
-			return fmt.Errorf("Tomb dying")
+			return tomb.ErrDying
 		}
 	}
 	panic("unreachable")
 }
 
-func (fw *PollingFileWatcher) ChangeEvents(origFi os.FileInfo) chan bool {
+func (fw *PollingFileWatcher) ChangeEvents(t tomb.Tomb, origFi os.FileInfo) chan bool {
 	ch := make(chan bool)
 	stop := make(chan bool)
 	var once sync.Once
@@ -64,6 +63,9 @@ func (fw *PollingFileWatcher) ChangeEvents(origFi os.FileInfo) chan bool {
 			select {
 			case <-stop:
 				return
+			case <-t.Dying():
+				once.Do(stopAndClose)
+				continue
 			default:
 			}
 
diff --git a/watch/watch.go b/watch/watch.go
index 7caa266..13fca2f 100644
--- a/watch/watch.go
+++ b/watch/watch.go
@@ -15,6 +15,6 @@ type FileWatcher interface {
 
 	// ChangeEvents returns a channel of events corresponding to the
 	// times the file is ready to be read.
-	ChangeEvents(os.FileInfo) chan bool
+	ChangeEvents(tomb.Tomb, os.FileInfo) chan bool
 }