Fixes from review:

* extra word typo in readme
* initialize timestamp field in init(), update tests
* always use string arrow type for tags

plugins/outputs/parquet/README.md

@@ -1,6 +1,6 @@
 # Parquet Output Plugin
 
-This plugin sends writes metrics to parquet files. By default, the parquet
+This plugin writes metrics to parquet files. By default, the parquet
 output groups metrics by metric name and write those metrics all to the same
 file. If a metric schema does not match then metrics are dropped.
 

plugins/outputs/parquet/parquet.go

@@ -22,6 +22,8 @@ import (
 //go:embed sample.conf
 var sampleConfig string
 
+var defaultTimestampFieldName = "timestamp"
+
 type metricGroup struct {
 	filename string
 	builder  *array.RecordBuilder
@@ -47,11 +49,6 @@ func (p *Parquet) Init() error {
 		p.Directory = "."
 	}
 
-	if p.TimestampFieldName == nil {
-		timestampFieldName := "timestamp"
-		p.TimestampFieldName = &timestampFieldName
-	}
-
 	stat, err := os.Stat(p.Directory)
 	if os.IsNotExist(err) {
 		if err := os.MkdirAll(p.Directory, 0750); err != nil {
@@ -255,11 +252,7 @@ func (p *Parquet) createSchema(metrics []telegraf.Metric) (*arrow.Schema, error)
 		}
 		for _, tag := range metric.TagList() {
 			if _, ok := rawFields[tag.Key]; !ok {
-				arrowType, err := goToArrowType(tag.Value)
-				if err != nil {
-					return nil, fmt.Errorf("error converting '%s=%s' tag to arrow type: %w", tag.Key, tag.Value, err)
-				}
-				rawFields[tag.Key] = arrowType
+				rawFields[tag.Key] = arrow.BinaryTypes.String
 			}
 		}
 	}
@@ -335,5 +328,9 @@ func goToArrowType(value interface{}) (arrow.DataType, error) {
 }
 
 func init() {
-	outputs.Add("parquet", func() telegraf.Output { return &Parquet{} })
+	outputs.Add("parquet", func() telegraf.Output {
+		return &Parquet{
+			TimestampFieldName: &defaultTimestampFieldName,
+		}
+	})
 }

plugins/outputs/parquet/parquet_test.go

@@ -125,7 +125,8 @@ func TestCases(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			testDir := t.TempDir()
 			plugin := &Parquet{
-				Directory: testDir,
+				Directory:          testDir,
+				TimestampFieldName: &defaultTimestampFieldName,
 			}
 			require.NoError(t, plugin.Init())
 			require.NoError(t, plugin.Connect())
@@ -161,8 +162,9 @@ func TestRotation(t *testing.T) {
 
 	testDir := t.TempDir()
 	plugin := &Parquet{
-		Directory:        testDir,
-		RotationInterval: config.Duration(1 * time.Second),
+		Directory:          testDir,
+		RotationInterval:   config.Duration(1 * time.Second),
+		TimestampFieldName: &defaultTimestampFieldName,
 	}
 
 	require.NoError(t, plugin.Init())
@@ -188,11 +190,9 @@ func TestOmitTimestamp(t *testing.T) {
 		),
 	}
 
-	emptyTimestamp := ""
 	testDir := t.TempDir()
 	plugin := &Parquet{
-		Directory:          testDir,
-		TimestampFieldName: &emptyTimestamp,
+		Directory: testDir,
 	}
 	require.NoError(t, plugin.Init())
 	require.NoError(t, plugin.Connect())