fix: snmp input plugin errors if mibs folder doesn't exist (influxdat…

…a#10346) (influxdata#10354)

internal/snmp/translate.go

@@ -54,11 +54,17 @@ func LoadMibsFromPath(paths []string, log telegraf.Logger) error {
 		}
 
 		appendPath(mibPath)
-		folders = append(folders, mibPath)
 		err := filepath.Walk(mibPath, func(path string, info os.FileInfo, err error) error {
 			if info == nil {
-				return fmt.Errorf("no mibs found")
+				log.Warnf("No mibs found")
+				if os.IsNotExist(err) {
+					log.Warnf("MIB path doesn't exist: %q", mibPath)
+				} else if err != nil {
+					return err
+				}
+				return nil
 			}
+			folders = append(folders, mibPath)
 			// symlinks are files so we need to double check if any of them are folders
 			// Will check file vs directory later on
 			if info.Mode()&os.ModeSymlink != 0 {
@@ -71,7 +77,7 @@ func LoadMibsFromPath(paths []string, log telegraf.Logger) error {
 			return nil
 		})
 		if err != nil {
-			return fmt.Errorf("Filepath could not be walked: %v", err)
+			return fmt.Errorf("Filepath %q could not be walked: %v", mibPath, err)
 		}
 
 		for _, folder := range folders {

plugins/inputs/snmp/snmp_test.go

@@ -1328,3 +1328,10 @@ func TestCanNotParse(t *testing.T) {
 	err := s.Init()
 	require.Error(t, err)
 }
+
+func TestMissingMibPath(t *testing.T) {
+	log := testutil.Logger{}
+	path := []string{"non-existing-directory"}
+	err := snmp.LoadMibsFromPath(path, log)
+	require.NoError(t, err)
+}