Remove remnants of config watcher (#18067)

The last part of config watching was in advanced logging.
We remove it from there too to keep things consistent.

https://community-daily.mattermost.com/plugins/focalboard/workspace/zyoahc9uapdn3xdptac6jb69ic?id=285b80a3-257d-41f6-8cf4-ed80ca9d92e5&v=495cdb4d-c13a-4992-8eb9-80cfee2819a4&c=a1b58527-6a3d-4faa-8144-166a3698731f

```release-note
Removed config watch feature from advanced logging config.
```

config/logging.go

@@ -110,8 +110,7 @@ type fileSrc struct {
 	mutex sync.RWMutex
 	cfg   mlog.LogTargetCfg
 
-	path    string
-	watcher *watcher
+	path string
 }
 
 func newFileSrc(path string, configStore *Store) (*fileSrc, error) {
@@ -156,24 +155,6 @@ func (src *fileSrc) Set(path string, configStore *Store) error {
 	src.mutex.Lock()
 	defer src.mutex.Unlock()
 
-	if src.watcher != nil {
-		if err = src.watcher.Close(); err != nil {
-			mlog.Error("Failed to close watcher", mlog.Err(err))
-		}
-		src.watcher = nil
-	}
-
-	watcher, err := newWatcher(path, func() {
-		if serr := src.Set(path, configStore); serr != nil {
-			mlog.Error("Failed to reload file on change", mlog.String("path", path), mlog.Err(serr))
-		}
-	})
-	if err != nil {
-		return err
-	}
-
-	src.watcher = watcher
-
 	return nil
 }
 
@@ -188,14 +169,7 @@ func (src *fileSrc) set(cfg mlog.LogTargetCfg) {
 
 // Close cleans up resources.
 func (src *fileSrc) Close() error {
-	var err error
-	src.mutex.Lock()
-	defer src.mutex.Unlock()
-	if src.watcher != nil {
-		err = src.watcher.Close()
-		src.watcher = nil
-	}
-	return err
+	return nil
 }
 
 func logTargetCfgFromJSON(data []byte) (mlog.LogTargetCfg, error) {

config/watcher.go

@@ -1,80 +0,0 @@
-// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
-// See LICENSE.txt for license information.
-
-package config
-
-import (
-	"path/filepath"
-
-	"github.com/fsnotify/fsnotify"
-	"github.com/pkg/errors"
-
-	"github.com/mattermost/mattermost-server/v6/shared/mlog"
-)
-
-// watcher monitors a file for changes
-type watcher struct {
-	fsWatcher *fsnotify.Watcher
-	close     chan struct{}
-	closed    chan struct{}
-}
-
-// newWatcher creates a new instance of watcher to monitor for file changes.
-func newWatcher(path string, callback func()) (w *watcher, err error) {
-	fsWatcher, err := fsnotify.NewWatcher()
-	if err != nil {
-		return nil, errors.Wrapf(err, "failed to create fsnotify watcher for %s", path)
-	}
-
-	path = filepath.Clean(path)
-
-	// Watch the entire containing directory.
-	configDir, _ := filepath.Split(path)
-	if err := fsWatcher.Add(configDir); err != nil {
-		if closeErr := fsWatcher.Close(); closeErr != nil {
-			mlog.Error("failed to stop fsnotify watcher for %s", mlog.String("path", path), mlog.Err(closeErr))
-		}
-		return nil, errors.Wrapf(err, "failed to watch directory %s", configDir)
-	}
-
-	w = &watcher{
-		fsWatcher: fsWatcher,
-		close:     make(chan struct{}),
-		closed:    make(chan struct{}),
-	}
-
-	go func() {
-		defer close(w.closed)
-		defer func() {
-			if err := fsWatcher.Close(); err != nil {
-				mlog.Error("failed to stop fsnotify watcher for %s", mlog.String("path", path))
-			}
-		}()
-
-		for {
-			select {
-			case event := <-fsWatcher.Events:
-				// We only care about the given file.
-				if filepath.Clean(event.Name) == path {
-					if event.Op&fsnotify.Write == fsnotify.Write || event.Op&fsnotify.Create == fsnotify.Create {
-						mlog.Info("Config file watcher detected a change", mlog.String("path", path))
-						go callback()
-					}
-				}
-			case err := <-fsWatcher.Errors:
-				mlog.Error("Failed while watching config file", mlog.String("path", path), mlog.Err(err))
-			case <-w.close:
-				return
-			}
-		}
-	}()
-
-	return w, nil
-}
-
-func (w *watcher) Close() error {
-	close(w.close)
-	<-w.closed
-
-	return nil
-}

config/watcher_test.go

@@ -1,63 +0,0 @@
-// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
-// See LICENSE.txt for license information.
-
-package config
-
-import (
-	"io/ioutil"
-	"os"
-	"path/filepath"
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/require"
-)
-
-func TestWatcherInvalidDirectory(t *testing.T) {
-	if testing.Short() {
-		t.Skip("skipping watcher test in short mode")
-	}
-
-	callback := func() {}
-	_, err := newWatcher("/does/not/exist", callback)
-	require.Error(t, err, "should have failed to watch a non-existent directory")
-}
-
-func TestWatcher(t *testing.T) {
-	if testing.Short() {
-		t.Skip("skipping watcher test in short mode")
-	}
-
-	tempDir, err := ioutil.TempDir("", "TestWatcher")
-	require.NoError(t, err)
-	defer os.RemoveAll(tempDir)
-
-	f, err := ioutil.TempFile(tempDir, "TestWatcher")
-	require.NoError(t, err)
-	defer f.Close()
-	defer os.Remove(f.Name())
-
-	called := make(chan bool)
-	callback := func() {
-		called <- true
-	}
-	watcher, err := newWatcher(f.Name(), callback)
-	require.NoError(t, err)
-	defer watcher.Close()
-
-	// Write to a different file
-	ioutil.WriteFile(filepath.Join(tempDir, "unrelated"), []byte("data"), 0644)
-	select {
-	case <-called:
-		require.Fail(t, "callback should not have been called for unrelated file")
-	case <-time.After(1 * time.Second):
-	}
-
-	// Write to the watched file
-	ioutil.WriteFile(f.Name(), []byte("data"), 0644)
-	select {
-	case <-called:
-	case <-time.After(5 * time.Second):
-		require.Fail(t, "callback should have been called when file written")
-	}
-}