Add configurable option for the 'path' tag override in the Tail plugin. (#9069)

* Add configurable option for the 'path' tag override in the Tail plugin.

* get test cases to pass

* update default config

* convert to configurable string field

plugins/inputs/tail/README.md

@@ -64,6 +64,9 @@ The plugin expects messages in one of the
   ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
   data_format = "influx"
 
+  ## Set the tag that will contain the path of the tailed file. If you don't want this tag, set it to an empty string.
+  # path_tag = "path"
+
   ## multiline parser/codec
   ## https://www.elastic.co/guide/en/logstash/2.4/plugins-filters-multiline.html
   #[inputs.tail.multiline]

plugins/inputs/tail/tail.go

@@ -40,6 +40,7 @@ type Tail struct {
 	WatchMethod         string   `toml:"watch_method"`
 	MaxUndeliveredLines int      `toml:"max_undelivered_lines"`
 	CharacterEncoding   string   `toml:"character_encoding"`
+	PathTag             string   `toml:"path_tag"`
 
 	Log        telegraf.Logger `toml:"-"`
 	tailers    map[string]*tail.Tail
@@ -70,6 +71,7 @@ func NewTail() *Tail {
 		FromBeginning:       false,
 		MaxUndeliveredLines: 1000,
 		offsets:             offsetsCopy,
+		PathTag:             "path",
 	}
 }
 
@@ -115,6 +117,9 @@ const sampleConfig = `
   ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
   data_format = "influx"
 
+  ## Set the tag that will contain the path of the tailed file. If you don't want this tag, set it to an empty string.
+  # path_tag = "path"
+
   ## multiline parser/codec
   ## https://www.elastic.co/guide/en/logstash/2.4/plugins-filters-multiline.html
   #[inputs.tail.multiline]
@@ -380,8 +385,10 @@ func (t *Tail) receiver(parser parsers.Parser, tailer *tail.Tail) {
 		}
 		firstLine = false
 
+		if t.PathTag != "" {
 			for _, metric := range metrics {
-			metric.AddTag("path", tailer.Filename)
+				metric.AddTag(t.PathTag, tailer.Filename)
+			}
 		}
 
 		// try writing out metric first without blocking

plugins/inputs/tail/tail_test.go

@@ -44,6 +44,7 @@ func NewTestTail() *Tail {
 		MaxUndeliveredLines: 1000,
 		offsets:             offsetsCopy,
 		WatchMethod:         watchMethod,
+		PathTag:             "path",
 	}
 }
 
@@ -357,6 +358,7 @@ func TestMultipleMetricsOnFirstLine(t *testing.T) {
 	plugin.Log = testutil.Logger{}
 	plugin.FromBeginning = true
 	plugin.Files = []string{tmpfile.Name()}
+	plugin.PathTag = "customPathTagMyFile"
 	plugin.SetParserFunc(func() (parsers.Parser, error) {
 		return json.New(
 			&json.Config{
@@ -379,7 +381,7 @@ func TestMultipleMetricsOnFirstLine(t *testing.T) {
 	expected := []telegraf.Metric{
 		testutil.MustMetric("cpu",
 			map[string]string{
-				"path": tmpfile.Name(),
+				"customPathTagMyFile": tmpfile.Name(),
 			},
 			map[string]interface{}{
 				"time_idle": 42.0,
@@ -387,7 +389,7 @@ func TestMultipleMetricsOnFirstLine(t *testing.T) {
 			time.Unix(0, 0)),
 		testutil.MustMetric("cpu",
 			map[string]string{
-				"path": tmpfile.Name(),
+				"customPathTagMyFile": tmpfile.Name(),
 			},
 			map[string]interface{}{
 				"time_idle": 42.0,