add grok as a top level parser

plugins/inputs/reader/reader_test.go

@@ -35,6 +35,23 @@ func TestJSONParserCompile(t *testing.T) {
 	assert.Equal(t, 5, len(acc.Metrics[0].Fields))
 }
 
+func TestGrokParser(t *testing.T) {
+	testDir := getPluginDir()
+	var acc testutil.Accumulator
+	r := Reader{
+		Filepaths:  []string{testDir + "/reader/testfiles/grok_a.log"},
+		DataFormat: "grok",
+		Patterns:   []string{"%{COMMON_LOG_FORMAT}"},
+	}
+
+	r.compileParser()
+	err := r.Gather(&acc)
+	log.Printf("err: %v", err)
+	log.Printf("metric[0]_tags: %v, metric[0]_fields: %v", acc.Metrics[0].Tags, acc.Metrics[0].Fields)
+	log.Printf("metric[1]_tags: %v, metric[1]_fields: %v", acc.Metrics[1].Tags, acc.Metrics[1].Fields)
+	t.Error()
+}
+
 func getPluginDir() string {
 	_, filename, _, _ := runtime.Caller(1)
 	return strings.Replace(filename, "/reader/reader_test.go", "", 1)