Support resolution of symlinks in filecount input (#6735)

plugins/inputs/filecount/README.md

@@ -27,6 +27,9 @@ Reports the number and total size of files in specified directories.
   ## Only count regular files. Defaults to true.
   regular_only = true
 
+  ## Follow all symlinks while walking the directory tree. Defaults to false.
+  follow_symlinks = false
+
   ## Only count files that are at least this size. If size is
   ## a negative number, only count files that are smaller than the
   ## absolute value of size. Acceptable units are B, KiB, MiB, KB, ...

plugins/inputs/filecount/filecount.go

@@ -35,6 +35,9 @@ const sampleConfig = `
   ## Only count regular files. Defaults to true.
   regular_only = true
 
+  ## Follow all symlinks while walking the directory tree. Defaults to false.
+  follow_symlinks = false
+
   ## Only count files that are at least this size. If size is
   ## a negative number, only count files that are smaller than the
   ## absolute value of size. Acceptable units are B, KiB, MiB, KB, ...
@@ -53,6 +56,7 @@ type FileCount struct {
 	Name           string
 	Recursive      bool
 	RegularOnly    bool
+	FollowSymlinks bool
 	Size           internal.Size
 	MTime          internal.Duration `toml:"mtime"`
 	fileFilters    []fileFilterFunc
@@ -208,6 +212,7 @@ func (fc *FileCount) count(acc telegraf.Accumulator, basedir string, glob globpa
 		Callback:             walkFn,
 		PostChildrenCallback: postChildrenFn,
 		Unsorted:             true,
+		FollowSymbolicLinks:  fc.FollowSymlinks,
 		ErrorCallback: func(osPathname string, err error) godirwalk.ErrorAction {
 			if os.IsPermission(errors.Cause(err)) {
 				fc.Log.Debug(err)
@@ -297,6 +302,7 @@ func NewFileCount() *FileCount {
 		Name:           "*",
 		Recursive:      true,
 		RegularOnly:    true,
+		FollowSymlinks: false,
 		Size:           internal.Size{Size: 0},
 		MTime:          internal.Duration{Duration: 0},
 		fileFilters:    nil,

plugins/inputs/filecount/filecount_test.go

@@ -102,7 +102,6 @@ func TestSizeFilter(t *testing.T) {
 }
 
 func TestMTimeFilter(t *testing.T) {
-
 	mtime := time.Date(2011, time.December, 14, 18, 25, 5, 0, time.UTC)
 	fileAge := time.Since(mtime) - (60 * time.Second)
 
@@ -119,6 +118,19 @@ func TestMTimeFilter(t *testing.T) {
 	fileCountEquals(t, fc, len(matches), 0)
 }
 
+// The library dependency karrick/godirwalk completely abstracts out the
+// behavior of the FollowSymlinks plugin input option. However, it should at
+// least behave identically when enabled on a filesystem with no symlinks.
+func TestFollowSymlinks(t *testing.T) {
+	fc := getNoFilterFileCount()
+	fc.FollowSymlinks = true
+	matches := []string{"foo", "bar", "baz", "qux",
+		"subdir/", "subdir/quux", "subdir/quuz",
+		"subdir/nested2", "subdir/nested2/qux"}
+
+	fileCountEquals(t, fc, len(matches), 5096)
+}
+
 // Paths with a trailing slash will not exactly match paths produced during the
 // walk as these paths are cleaned before being returned from godirwalk. #6329
 func TestDirectoryWithTrailingSlash(t *testing.T) {