Repository: numaproj/numaflow (go)

Issue:
eventTimeExtractor to support keys
# Summary

I found that the [Event Time Extractor Spec](https://numaflow.numaproj.io/user-guide/sources/transformer/builtin-transformers/event-time-extractor/#event-time-extractor-spec) ignores the keys when reading from a Kafka source. Guess the relevant code is [here](https://github.com/numaproj/numaflow/blob/2189ea9ec23368a9fdebaa72667b85c0fe9c4fc2/pkg/sources/transformer/builtin/event_time/event_time_extractor.go#L59C27-L59C39).

Proposing to use the source keys (for example Kafka keys) and set them in the output messages.

# Use Cases

Generally speaking eventTimeExtractor doesn't work with keyed sources.

Actually, we don't key our Kafka streams. But the above can still lead to buggy behaviour.
I have two Kafka topics where events are produced without keys. Kafka appears to represent no keys with an empty string "" by default (at least in our setup).
1. The first topic is read by eventTimeExtractor. The output has `keys=[]` (should be `[""]`)
2. The second topic is read by a custom `sourcetransformer`. Keys are passed through in the `handler`. The output is `keys=[""]`.
3. The downstreams vertices (mapper) incorrectly handles the two sources as separate keyed-streams, so the won't be joined in reducer vertices.

---
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Pull request description:
fix: builtin transformer should keep the keys
fixes #2043 

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Patch:
diff --git a/pkg/sources/transformer/builtin/event_time/event_time_extractor.go b/pkg/sources/transformer/builtin/event_time/event_time_extractor.go
index ff143f2c..c844c518 100644
--- a/pkg/sources/transformer/builtin/event_time/event_time_extractor.go
+++ b/pkg/sources/transformer/builtin/event_time/event_time_extractor.go
@@ -56,7 +56,7 @@ func New(args map[string]string) (sourcetransformer.SourceTransformFunc, error)
 
 	return func(ctx context.Context, keys []string, datum sourcetransformer.Datum) sourcetransformer.Messages {
 		log := logging.FromContext(ctx)
-		resultMsg, err := e.apply(datum.Value(), datum.EventTime())
+		resultMsg, err := e.apply(datum.Value(), datum.EventTime(), keys)
 		if err != nil {
 			log.Warnf("event time extractor got an error: %v, skip updating event time...", err)
 		}
@@ -66,10 +66,10 @@ func New(args map[string]string) (sourcetransformer.SourceTransformFunc, error)
 
 // apply compiles the payload to extract the new event time. If there is any error during extraction,
 // we pass on the original input event time. Otherwise, we assign the new event time to the message.
-func (e eventTimeExtractor) apply(payload []byte, et time.Time) (sourcetransformer.Message, error) {
+func (e eventTimeExtractor) apply(payload []byte, et time.Time, keys []string) (sourcetransformer.Message, error) {
 	timeStr, err := expr.EvalStr(e.expression, payload)
 	if err != nil {
-		return sourcetransformer.NewMessage(payload, et), err
+		return sourcetransformer.NewMessage(payload, et).WithKeys(keys), err
 	}
 
 	var newEventTime time.Time
@@ -80,8 +80,8 @@ func (e eventTimeExtractor) apply(payload []byte, et time.Time) (sourcetransform
 		newEventTime, err = dateparse.ParseStrict(timeStr)
 	}
 	if err != nil {
-		return sourcetransformer.NewMessage(payload, et), err
+		return sourcetransformer.NewMessage(payload, et).WithKeys(keys), err
 	} else {
-		return sourcetransformer.NewMessage(payload, newEventTime), nil
+		return sourcetransformer.NewMessage(payload, newEventTime).WithKeys(keys), nil
 	}
 }
diff --git a/pkg/sources/transformer/builtin/filter/filter.go b/pkg/sources/transformer/builtin/filter/filter.go
index 08f47795..c30b9901 100644
--- a/pkg/sources/transformer/builtin/filter/filter.go
+++ b/pkg/sources/transformer/builtin/filter/filter.go
@@ -32,17 +32,17 @@ type filter struct {
 }
 
 func New(args map[string]string) (sourcetransformer.SourceTransformFunc, error) {
-	expr, existing := args["expression"]
+	exp, existing := args["expression"]
 	if !existing {
 		return nil, fmt.Errorf(`missing "expression"`)
 	}
 	f := filter{
-		expression: expr,
+		expression: exp,
 	}
 
 	return func(ctx context.Context, keys []string, datum sourcetransformer.Datum) sourcetransformer.Messages {
 		log := logging.FromContext(ctx)
-		resultMsg, err := f.apply(datum.EventTime(), datum.Value())
+		resultMsg, err := f.apply(datum.EventTime(), datum.Value(), keys)
 		if err != nil {
 			log.Errorf("Filter map function apply got an error: %v", err)
 		}
@@ -50,13 +50,13 @@ func New(args map[string]string) (sourcetransformer.SourceTransformFunc, error)
 	}, nil
 }
 
-func (f filter) apply(et time.Time, msg []byte) (sourcetransformer.Message, error) {
+func (f filter) apply(et time.Time, msg []byte, keys []string) (sourcetransformer.Message, error) {
 	result, err := expr.EvalBool(f.expression, msg)
 	if err != nil {
 		return sourcetransformer.MessageToDrop(et), err
 	}
 	if result {
-		return sourcetransformer.NewMessage(msg, et), nil
+		return sourcetransformer.NewMessage(msg, et).WithKeys(keys), nil
 	}
 	return sourcetransformer.MessageToDrop(et), nil
 }
diff --git a/pkg/sources/transformer/builtin/time_extraction_filter/time_extraction_filter.go b/pkg/sources/transformer/builtin/time_extraction_filter/time_extraction_filter.go
index 112c5de2..bb1515cb 100644
--- a/pkg/sources/transformer/builtin/time_extraction_filter/time_extraction_filter.go
+++ b/pkg/sources/transformer/builtin/time_extraction_filter/time_extraction_filter.go
@@ -59,7 +59,7 @@ func New(args map[string]string) (sourcetransformer.SourceTransformFunc, error)
 
 	return func(ctx context.Context, keys []string, datum sourcetransformer.Datum) sourcetransformer.Messages {
 		log := logging.FromContext(ctx)
-		resultMsg, err := e.apply(datum.EventTime(), datum.Value())
+		resultMsg, err := e.apply(datum.EventTime(), datum.Value(), keys)
 		if err != nil {
 			log.Errorf("Filter or event time extractor got an error: %v", err)
 		}
@@ -68,7 +68,7 @@ func New(args map[string]string) (sourcetransformer.SourceTransformFunc, error)
 
 }
 
-func (e expressions) apply(et time.Time, payload []byte) (sourcetransformer.Message, error) {
+func (e expressions) apply(et time.Time, payload []byte, keys []string) (sourcetransformer.Message, error) {
 	result, err := expr.EvalBool(e.filterExpr, payload)
 	if err != nil {
 		return sourcetransformer.MessageToDrop(et), err
@@ -76,7 +76,7 @@ func (e expressions) apply(et time.Time, payload []byte) (sourcetransformer.Mess
 	if result {
 		timeStr, err := expr.EvalStr(e.eventTimeExpr, payload)
 		if err != nil {
-			return sourcetransformer.NewMessage(payload, et), err
+			return sourcetransformer.NewMessage(payload, et).WithKeys(keys), err
 		}
 		var newEventTime time.Time
 		time.Local, _ = time.LoadLocation("UTC")
@@ -86,9 +86,9 @@ func (e expressions) apply(et time.Time, payload []byte) (sourcetransformer.Mess
 			newEventTime, err = dateparse.ParseStrict(timeStr)
 		}
 		if err != nil {
-			return sourcetransformer.NewMessage(payload, et), err
+			return sourcetransformer.NewMessage(payload, et).WithKeys(keys), err
 		} else {
-			return sourcetransformer.NewMessage(payload, newEventTime), nil
+			return sourcetransformer.NewMessage(payload, newEventTime).WithKeys(keys), nil
 		}
 	}
 	return sourcetransformer.MessageToDrop(et), nil


Test patch:
diff --git a/pkg/sources/transformer/builtin/event_time/event_time_extractor_test.go b/pkg/sources/transformer/builtin/event_time/event_time_extractor_test.go
index 22fc6b63..d14e37be 100644
--- a/pkg/sources/transformer/builtin/event_time/event_time_extractor_test.go
+++ b/pkg/sources/transformer/builtin/event_time/event_time_extractor_test.go
@@ -24,6 +24,8 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+var _keys = []string{"test-key"}
+
 type testDatum struct {
 	value     []byte
 	eventTime time.Time
@@ -74,7 +76,7 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.NoError(t, err)
 
 		testJsonMsg := `{"test": 21, "item": [{"id": 1, "name": "numa", "time": "2022-02-18T21:54:42.123Z"},{"id": 2, "name": "numa", "time": "2021-02-18T21:54:42.123Z"}]}`
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: time.Time{},
 			watermark: time.Time{},
@@ -86,6 +88,8 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.True(t, expected.Equal(result.Items()[0].EventTime()))
 		// Verify the payload remains unchanged.
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// Verify the keys remain unchanged.
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 
 	t.Run("Json expression valid, assign a new event time to the message - format specified", func(t *testing.T) {
@@ -94,7 +98,7 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.NoError(t, err)
 
 		testJsonMsg := `{"test": 21, "item": [{"id": 1, "name": "numa", "time": "2022-02-18T21:54:42.123Z"},{"id": 2, "name": "numa", "time": "2021-02-18T21:54:42.123Z"}]}`
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: time.Time{},
 			watermark: time.Time{},
@@ -106,6 +110,8 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.True(t, expected.Equal(result.Items()[0].EventTime()))
 		// Verify the payload remains unchanged.
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// Verify the keys remain unchanged.
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 
 	t.Run("Time string not matching user-provided format, pass on the message without assigning new event time", func(t *testing.T) {
@@ -114,9 +120,9 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.NoError(t, err)
 
 		testInputEventTime := time.Date(2022, 1, 4, 2, 3, 4, 5, time.UTC)
-		// Handler receives format as time.ANSIC but in the message, we use time.RFC3339. Format is not matched.
+		// Handler receives a format as time.ANSIC but in the message, we use time.RFC3339. Format is not matched.
 		testJsonMsg := `{"test": 21, "item": [{"id": 1, "name": "numa", "time": "2022-02-18T21:54:42.123Z"},{"id": 2, "name": "numa", "time": "2021-02-18T21:54:42.123Z"}]}`
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: testInputEventTime,
 			watermark: time.Time{},
@@ -126,6 +132,8 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.Equal(t, testInputEventTime, result.Items()[0].EventTime())
 		// Verify the payload remains unchanged.
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// Verify the keys remain unchanged.
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 
 	t.Run("Cannot compile json expression, pass on the message without assigning new event time", func(t *testing.T) {
@@ -135,7 +143,7 @@ func TestEventTimeExtractor(t *testing.T) {
 
 		testInputEventTime := time.Date(2022, 1, 4, 2, 3, 4, 5, time.UTC)
 		testJsonMsg := `{"test": 21, "item": [{"id": 1, "name": "numa", "time": "2022-02-18T21:54:42.123Z"},{"id": 2, "name": "numa", "time": "2021-02-18T21:54:42.123Z"}]}`
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: testInputEventTime,
 			watermark: time.Time{},
@@ -146,6 +154,8 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.True(t, expected.Equal(result.Items()[0].EventTime()))
 		// Verify the payload remains unchanged.
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// Verify the keys remain unchanged.
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 
 	t.Run("The time string is in epoch format with a granularity of seconds, assign a new event time to the message", func(t *testing.T) {
@@ -154,9 +164,9 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.NoError(t, err)
 
 		testInputEventTime := time.Date(2022, 1, 4, 2, 3, 4, 5, time.UTC)
-		// Handler receives format as time.ANSIC but in the message, we use time.RFC3339. Format is not matched.
+		// Handler receives a format as time.ANSIC but in the message, we use time.RFC3339. Format is not matched.
 		testJsonMsg := `{"test": 21, "item": [{"id": 1, "name": "numa", "time": "1673239888"},{"id": 2, "name": "numa", "time": "1673239888"}]}`
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: testInputEventTime,
 			watermark: time.Time{},
@@ -168,6 +178,8 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.True(t, expected.Equal(result.Items()[0].EventTime()))
 		// Verify the payload remains unchanged.
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// Verify the keys remain unchanged.
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 
 	t.Run("The time string is in epoch format with a granularity of milliseconds, assign a new event time to the message", func(t *testing.T) {
@@ -177,7 +189,7 @@ func TestEventTimeExtractor(t *testing.T) {
 
 		testInputEventTime := time.Date(2022, 1, 4, 2, 3, 4, 5, time.UTC)
 		testJsonMsg := `{"test": 21, "item": [{"id": 1, "name": "numa", "time": "1673239888123"},{"id": 2, "name": "numa", "time": "1673239888123"}]}`
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: testInputEventTime,
 			watermark: time.Time{},
@@ -189,6 +201,8 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.True(t, expected.Equal(result.Items()[0].EventTime()))
 		// Verify the payload remains unchanged.
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// Verify the keys remain unchanged.
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 
 	t.Run("The time string is ambiguous, pass on the message without assigning new event time", func(t *testing.T) {
@@ -199,7 +213,7 @@ func TestEventTimeExtractor(t *testing.T) {
 		testInputEventTime := time.Date(2022, 1, 4, 2, 3, 4, 5, time.UTC)
 		// 04/08/2014 is ambiguous because it could be mm/dd/yyyy or dd/mm/yyyy.
 		testJsonMsg := `{"test": 21, "item": [{"id": 1, "name": "numa", "time": "04/08/2014 22:05"},{"id": 2, "name": "numa", "time": "04/08/2014 22:05"}]}`
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: testInputEventTime,
 			watermark: time.Time{},
@@ -211,5 +225,7 @@ func TestEventTimeExtractor(t *testing.T) {
 		assert.True(t, expected.Equal(result.Items()[0].EventTime()))
 		// Verify the payload remains unchanged.
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// Verify the keys remain unchanged.
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 }
diff --git a/pkg/sources/transformer/builtin/filter/filter_test.go b/pkg/sources/transformer/builtin/filter/filter_test.go
index 8ac227bd..fb0d7a57 100644
--- a/pkg/sources/transformer/builtin/filter/filter_test.go
+++ b/pkg/sources/transformer/builtin/filter/filter_test.go
@@ -22,6 +22,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/numaproj/numaflow-go/pkg/sourcetransformer"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -86,6 +87,7 @@ func TestExpression(t *testing.T) {
 			watermark: time.Time{},
 		})
 		assert.Equal(t, jsonMsg, string(result.Items()[0].Value()))
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 
 	t.Run("invalid expression", func(t *testing.T) {
@@ -99,7 +101,7 @@ func TestExpression(t *testing.T) {
 			eventTime: time.Time{},
 			watermark: time.Time{},
 		})
-		assert.Equal(t, "", string(result.Items()[0].Value()))
+		assert.Equal(t, sourcetransformer.MessageToDrop(time.Time{}), result.Items()[0])
 	})
 
 	t.Run("Json expression invalid", func(t *testing.T) {
@@ -113,7 +115,7 @@ func TestExpression(t *testing.T) {
 			eventTime: time.Time{},
 			watermark: time.Time{},
 		})
-		assert.Equal(t, "", string(result.Items()[0].Value()))
+		assert.Equal(t, sourcetransformer.MessageToDrop(time.Time{}), result.Items()[0])
 	})
 
 	t.Run("String expression invalid", func(t *testing.T) {
@@ -127,7 +129,7 @@ func TestExpression(t *testing.T) {
 			eventTime: time.Time{},
 			watermark: time.Time{},
 		})
-		assert.Equal(t, "", string(result.Items()[0].Value()))
+		assert.Equal(t, sourcetransformer.MessageToDrop(time.Time{}), result.Items()[0])
 	})
 
 	t.Run("base64 expression valid", func(t *testing.T) {
@@ -142,6 +144,7 @@ func TestExpression(t *testing.T) {
 			watermark: time.Time{},
 		})
 		assert.Equal(t, base64Msg, string(result.Items()[0].Value()))
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 
 	t.Run("event time unchanged", func(t *testing.T) {
@@ -157,5 +160,6 @@ func TestExpression(t *testing.T) {
 			watermark: time.Time{},
 		})
 		assert.Equal(t, testEventTime, result.Items()[0].EventTime())
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
 }
diff --git a/pkg/sources/transformer/builtin/time_extraction_filter/time_extraction_filter_test.go b/pkg/sources/transformer/builtin/time_extraction_filter/time_extraction_filter_test.go
index 02631c25..a178ce25 100644
--- a/pkg/sources/transformer/builtin/time_extraction_filter/time_extraction_filter_test.go
+++ b/pkg/sources/transformer/builtin/time_extraction_filter/time_extraction_filter_test.go
@@ -21,9 +21,12 @@ import (
 	"testing"
 	"time"
 
+	"github.com/numaproj/numaflow-go/pkg/sourcetransformer"
 	"github.com/stretchr/testify/assert"
 )
 
+var _keys = []string{"test-key"}
+
 type testDatum struct {
 	value     []byte
 	eventTime time.Time
@@ -66,7 +69,6 @@ var (
 )
 
 func TestFilterEventTime(t *testing.T) {
-
 	t.Run("Missing both expressions, return error", func(t *testing.T) {
 		_, err := New(map[string]string{})
 		assert.Error(t, err)
@@ -89,14 +91,16 @@ func TestFilterEventTime(t *testing.T) {
 		handle, err := New(map[string]string{"filterExpr": "int(json(payload).item[1].id) == 2", "eventTimeExpr": "json(payload).item[1].time", "eventTimeFormat": time.RFC3339})
 		assert.NoError(t, err)
 
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: time.Time{},
 			watermark: time.Time{},
 		})
 
-		// check that messsage has not changed
+		// check that message has not changed
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// check that keys have not changed
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 
 		// check that event time has changed
 		time.Local, _ = time.LoadLocation("UTC")
@@ -108,13 +112,13 @@ func TestFilterEventTime(t *testing.T) {
 		handle, err := New(map[string]string{"filterExpr": "int(json(payload).item[1].id) == 3", "eventTimeExpr": "json(payload).item[1].time", "eventTimeFormat": time.RFC3339})
 		assert.NoError(t, err)
 
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: time.Time{},
 			watermark: time.Time{},
 		})
 
-		assert.Equal(t, "", string(result.Items()[0].Value()))
+		assert.Equal(t, sourcetransformer.MessageToDrop(time.Time{}), result.Items()[0])
 	})
 
 	t.Run("Valid JSON expression for filter, incorrect format to eventTime", func(t *testing.T) {
@@ -122,14 +126,17 @@ func TestFilterEventTime(t *testing.T) {
 		assert.NoError(t, err)
 
 		testInputEventTime := time.Date(2022, 1, 4, 2, 3, 4, 5, time.UTC)
-		result := handle(context.Background(), []string{"test-key"}, &testDatum{
+		result := handle(context.Background(), _keys, &testDatum{
 			value:     []byte(testJsonMsg),
 			eventTime: testInputEventTime,
 			watermark: time.Time{},
 		})
 
+		// check that message event time has not changed
 		assert.Equal(t, testInputEventTime, result.Items()[0].EventTime())
+		// check that message has not changed
 		assert.Equal(t, testJsonMsg, string(result.Items()[0].Value()))
+		// check that keys have not been added
+		assert.Equal(t, _keys, result.Items()[0].Keys())
 	})
-
 }