feat(agent): Watch default config files if none specified (#13774)

cmd/telegraf/telegraf.go

@@ -232,10 +232,13 @@ func (t *Telegraf) loadConfiguration() (*config.Config, error) {
 		configFiles = append(configFiles, files...)
 	}
 
-	// providing no "config" or "config-directory" flag(s) should load default
-	// configuration files
+	// load default config paths if none are found
 	if len(configFiles) == 0 {
-		configFiles = append(configFiles, "")
+		defaultFiles, err := config.GetDefaultConfigPath()
+		if err != nil {
+			return nil, fmt.Errorf("unable to load default config paths: %w", err)
+		}
+		configFiles = append(configFiles, defaultFiles...)
 	}
 
 	t.configFiles = configFiles

config/config.go

@@ -441,30 +441,17 @@ func isURL(str string) bool {
 
 // LoadConfig loads the given config files and applies it to c
 func (c *Config) LoadConfig(path string) error {
-	var err error
-	paths := []string{}
-
-	if path == "" {
-		if paths, err = GetDefaultConfigPath(); err != nil {
-			return err
-		}
-	} else {
-		paths = append(paths, path)
+	if !c.Agent.Quiet {
+		log.Printf("I! Loading config: %s", path)
 	}
 
-	for _, path := range paths {
-		if !c.Agent.Quiet {
-			log.Printf("I! Loading config: %s", path)
-		}
+	data, _, err := LoadConfigFile(path)
+	if err != nil {
+		return fmt.Errorf("error loading config file %s: %w", path, err)
+	}
 
-		data, _, err := LoadConfigFile(path)
-		if err != nil {
-			return fmt.Errorf("error loading config file %s: %w", path, err)
-		}
-
-		if err = c.LoadConfigData(data); err != nil {
-			return fmt.Errorf("error loading config file %s: %w", path, err)
-		}
+	if err = c.LoadConfigData(data); err != nil {
+		return fmt.Errorf("error loading config file %s: %w", path, err)
 	}
 
 	return nil

config/config_test.go

@@ -446,6 +446,7 @@ func TestConfig_AzureMonitorNamespacePrefix(t *testing.T) {
 func TestGetDefaultConfigPathFromEnvURL(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
+		_, _ = w.Write([]byte("[agent]\ndebug = true"))
 	}))
 	defer ts.Close()
 
@@ -454,8 +455,7 @@ func TestGetDefaultConfigPathFromEnvURL(t *testing.T) {
 	configPath, err := config.GetDefaultConfigPath()
 	require.NoError(t, err)
 	require.Equal(t, []string{ts.URL}, configPath)
-	err = c.LoadConfig("")
-	require.NoError(t, err)
+	require.NoError(t, c.LoadConfig(configPath[0]))
 }
 
 func TestConfig_URLLikeFileName(t *testing.T) {