fix(config): set default parser (#12076)

config/config.go

@@ -689,9 +689,12 @@ func (c *Config) addAggregator(name string, table *ast.Table) error {
 	return nil
 }
 
-func (c *Config) probeParser(table *ast.Table) bool {
+func (c *Config) probeParser(parentcategory string, parentname string, table *ast.Table) bool {
 	var dataformat string
 	c.getFieldString(table, "data_format", &dataformat)
+	if dataformat == "" {
+		dataformat = setDefaultParser(parentcategory, parentname)
+	}
 
 	creator, ok := parsers.Parsers[dataformat]
 	if !ok {
@@ -709,15 +712,10 @@ func (c *Config) probeParser(table *ast.Table) bool {
 func (c *Config) addParser(parentcategory, parentname string, table *ast.Table) (*models.RunningParser, error) {
 	var dataformat string
 	c.getFieldString(table, "data_format", &dataformat)
-
 	if dataformat == "" {
-		if parentcategory == "inputs" && parentname == "exec" {
-			// Legacy support, exec plugin originally parsed JSON by default.
-			dataformat = "json"
-		} else {
-			dataformat = "influx"
-		}
+		dataformat = setDefaultParser(parentcategory, parentname)
 	}
+
 	var influxParserType string
 	c.getFieldString(table, "influx_parser_type", &influxParserType)
 	if dataformat == "influx" && influxParserType == "upstream" {
@@ -828,7 +826,7 @@ func (c *Config) setupProcessor(name string, creator processors.StreamingCreator
 	}
 
 	if t, ok := processor.(telegraf.ParserFuncPlugin); ok {
-		if !c.probeParser(table) {
+		if !c.probeParser("processors", name, table) {
 			return nil, false, errors.New("parser not found")
 		}
 		t.SetParserFunc(func() (telegraf.Parser, error) {
@@ -946,7 +944,7 @@ func (c *Config) addInput(name string, table *ast.Table) error {
 
 	if t, ok := input.(telegraf.ParserFuncPlugin); ok {
 		missCountThreshold = 1
-		if !c.probeParser(table) {
+		if !c.probeParser("inputs", name, table) {
 			return errors.New("parser not found")
 		}
 		t.SetParserFunc(func() (telegraf.Parser, error) {
@@ -957,7 +955,7 @@ func (c *Config) addInput(name string, table *ast.Table) error {
 	if t, ok := input.(parsers.ParserFuncInput); ok {
 		// DEPRECATED: Please switch your plugin to telegraf.ParserFuncPlugin.
 		missCountThreshold = 1
-		if !c.probeParser(table) {
+		if !c.probeParser("inputs", name, table) {
 			return errors.New("parser not found")
 		}
 		t.SetParserFunc(func() (parsers.Parser, error) {
@@ -1431,6 +1429,15 @@ func keys(m map[string]bool) []string {
 	return result
 }
 
+func setDefaultParser(category string, name string) string {
+	// Legacy support, exec plugin originally parsed JSON by default.
+	if category == "inputs" && name == "exec" {
+		return "json"
+	}
+
+	return "influx"
+}
+
 func (c *Config) hasErrs() bool {
 	return len(c.errs) > 0
 }

config/config_test.go

@@ -265,6 +265,16 @@ func TestConfig_WrongCertPath(t *testing.T) {
 	require.Error(t, c.LoadConfig("./testdata/wrong_cert_path.toml"))
 }
 
+func TestConfig_DefaultParser(t *testing.T) {
+	c := NewConfig()
+	require.NoError(t, c.LoadConfig("./testdata/default_parser.toml"))
+}
+
+func TestConfig_DefaultExecParser(t *testing.T) {
+	c := NewConfig()
+	require.NoError(t, c.LoadConfig("./testdata/default_parser_exec.toml"))
+}
+
 func TestConfig_LoadSpecialTypes(t *testing.T) {
 	c := NewConfig()
 	require.NoError(t, c.LoadConfig("./testdata/special_types.toml"))
@@ -886,6 +896,7 @@ type MockupInputPlugin struct {
 	Paths        []string `toml:"paths"`
 	Port         int      `toml:"port"`
 	Command      string
+	Files        []string
 	PidFile      string
 	Log          telegraf.Logger `toml:"-"`
 	tls.ServerConfig
@@ -1069,6 +1080,9 @@ func init() {
 	inputs.Add("exec", func() telegraf.Input {
 		return &MockupInputPlugin{Timeout: Duration(time.Second * 5)}
 	})
+	inputs.Add("file", func() telegraf.Input {
+		return &MockupInputPlugin{}
+	})
 	inputs.Add("http_listener_v2", func() telegraf.Input {
 		return &MockupInputPlugin{}
 	})

config/testdata/default_parser.toml

@@ -0,0 +1,2 @@
+[[inputs.file]]
+   files = ["metrics"]

config/testdata/default_parser_exec.toml

@@ -0,0 +1,2 @@
+[[inputs.exec]]
+  command = '/usr/bin/echo {"value": 42}'