[Go SDK + Protos] Fix Proto Spec for Pane encoding + Go SDK implementation.

CHANGES.md

@@ -107,7 +107,7 @@
   * Fixed session window aggregation, which wasn't being performed per-key. ([#33542](https://github.com/apache/beam/issues/33542)).)
 * [Dataflow Streaming Appliance] Fixed commits failing with KeyCommitTooLargeException when a key outputs >180MB of results. [#33588](https://github.com/apache/beam/issues/33588).
 * Fixed a Dataflow template creation issue that ignores template file creation errors (Java) ([#33636](https://github.com/apache/beam/issues/33636))
-
+* Correctly documented Pane Encodings in the portability protocols ([#33840](https://github.com/apache/beam/issues/33840)).
 
 ## Security Fixes
 * Fixed (CVE-YYYY-NNNN)[https://www.cve.org/CVERecord?id=CVE-YYYY-NNNN] (Java/Python/Go) ([#X](https://github.com/apache/beam/issues/X)).

model/pipeline/src/main/proto/org/apache/beam/model/pipeline/v1/beam_runner_api.proto

@@ -594,6 +594,9 @@ message BagStateSpec {
   string element_coder_id = 1;
 }
 
+// OrderedListState values are encoded with the var int encoded
+// millis-since-epoch followed by the value encoded by the provided coder.
+// Be aware this is not the standard timestamp value encoding.
 message OrderedListStateSpec {
   string element_coder_id = 1;
 }
@@ -946,15 +949,15 @@ message StandardCoders {
     //     coder.
     //
     //   pane - The first byte of the pane info determines which type of
-    //     encoding is used, as well as the is_first, is_last, and timing
+    //     encoding is used, as well as the is_first, is_last and timing
     //     fields. If this byte is bits [0 1 2 3 4 5 6 7], then:
     //     * bits [0 1 2 3] determine the encoding as follows:
     //         0000 - The entire pane info is encoded as a single byte.
     //                The is_first, is_last, and timing fields are encoded
     //                as below, and the index and non-speculative index are
     //                both zero (and hence are not encoded here).
     //         0001 - The pane info is encoded as this byte plus a single
-    //                VarInt encoed integer representing the pane index. The
+    //                VarInt encoded integer representing the pane index. The
     //                non-speculative index can be derived as follows:
     //                  -1 if the pane is early, otherwise equal to index.
     //         0010 - The pane info is encoded as this byte plus two VarInt
@@ -965,8 +968,10 @@ message StandardCoders {
     //         01 - on time
     //         10 - late
     //         11 - unknown
-    //     * bit 6 is 1 if this is the first pane, 0 otherwise.
-    //     * bit 7 is 1 if this is the last pane, 0 otherwise.
+    //     * bit 6 is 1 if this is the last pane, 0 otherwise. 
+    //         Commonly set with `byte |= 0x02`
+    //     * bit 7 is 1 if this is the first pane, 0 otherwise.
+    //         Commonly set with `byte |= 0x01`
     //
     //   element - The element incoded using the supplied element coder.
     //
@@ -1329,7 +1334,7 @@ message Trigger {
   message AfterSynchronizedProcessingTime {
   }
 
-  // The default trigger. Equivalent to Repeat { AfterEndOfWindow } but
+  // The default trigger. Equivalent to AfterEndOfWindow { Late: Always }} but
   // specially denoted to indicate the user did not alter the triggering.
   message Default {
   }
@@ -1339,12 +1344,12 @@ message Trigger {
     int32 element_count = 1;
   }
 
-  // Never ready. There will only be an ON_TIME output and a final
-  // output at window expiration.
+  // Never ready. There will only be an ON_TIME final output at window
+  // expiration.
   message Never {
   }
 
-  // Always ready. This can also be expressed as ElementCount(1) but
+  // Always ready. This can also be expressed as Repeat{ ElementCount(1) } but
   // is more explicit.
   message Always {
   }

sdks/go/pkg/beam/core/graph/coder/panes.go

@@ -29,10 +29,10 @@ func EncodePane(v typex.PaneInfo, w io.Writer) error {
 
 	pane := byte(0)
 	if v.IsFirst {
-		pane |= 0x02
+		pane |= 0x01
 	}
 	if v.IsLast {
-		pane |= 0x01
+		pane |= 0x02
 	}
 	pane |= byte(v.Timing << 2)
 
@@ -64,10 +64,10 @@ func EncodePane(v typex.PaneInfo, w io.Writer) error {
 func NewPane(b byte) typex.PaneInfo {
 	pn := typex.NoFiringPane()
 
-	if !(b&0x02 == 2) {
+	if !(b&0x01 == 1) {
 		pn.IsFirst = false
 	}
-	if !(b&0x01 == 1) {
+	if !(b&0x02 == 2) {
 		pn.IsLast = false
 	}
 

sdks/go/pkg/beam/core/graph/coder/panes_test.go

@@ -33,12 +33,13 @@ func equalPanes(left, right typex.PaneInfo) bool {
 
 func TestPaneCoder(t *testing.T) {
 	tests := []struct {
-		name    string
-		timing  typex.PaneTiming
-		first   bool
-		last    bool
-		index   int64
-		nsIndex int64
+		name      string
+		timing    typex.PaneTiming
+		first     bool
+		last      bool
+		index     int64
+		nsIndex   int64
+		firstByte byte
 	}{
 		{
 			"false bools",
@@ -47,6 +48,7 @@ func TestPaneCoder(t *testing.T) {
 			false,
 			0,
 			0,
+			0b00001100,
 		},
 		{
 			"true bools",
@@ -55,6 +57,7 @@ func TestPaneCoder(t *testing.T) {
 			true,
 			0,
 			0,
+			0b00001111,
 		},
 		{
 			"first pane",
@@ -63,6 +66,7 @@ func TestPaneCoder(t *testing.T) {
 			false,
 			0,
 			0,
+			0b00001101,
 		},
 		{
 			"last pane",
@@ -71,6 +75,7 @@ func TestPaneCoder(t *testing.T) {
 			true,
 			0,
 			0,
+			0b00001110,
 		},
 		{
 			"on time, different index and non-speculative",
@@ -79,6 +84,7 @@ func TestPaneCoder(t *testing.T) {
 			false,
 			1,
 			2,
+			0b00100100,
 		},
 		{
 			"valid early pane",
@@ -87,6 +93,7 @@ func TestPaneCoder(t *testing.T) {
 			false,
 			math.MaxInt64,
 			-1,
+			0b00010001,
 		},
 		{
 			"on time, max non-speculative index",
@@ -95,6 +102,7 @@ func TestPaneCoder(t *testing.T) {
 			true,
 			0,
 			math.MaxInt64,
+			0b00100110,
 		},
 		{
 			"late pane, max index",
@@ -103,6 +111,7 @@ func TestPaneCoder(t *testing.T) {
 			false,
 			math.MaxInt64,
 			0,
+			0b00101000,
 		},
 		{
 			"on time, min non-speculative index",
@@ -111,6 +120,7 @@ func TestPaneCoder(t *testing.T) {
 			true,
 			0,
 			math.MinInt64,
+			0b00100110,
 		},
 		{
 			"late, min index",
@@ -119,6 +129,34 @@ func TestPaneCoder(t *testing.T) {
 			false,
 			math.MinInt64,
 			0,
+			0b00101000,
+		},
+		{
+			"last late firing",
+			typex.PaneLate,
+			false,
+			true,
+			2,
+			1,
+			0b00101010,
+		},
+		{
+			"encodeByte 41",
+			typex.PaneLate,
+			true,
+			false,
+			2,
+			1,
+			0b00101001, // 41
+		},
+		{
+			"encodeByte 18",
+			typex.PaneEarly,
+			false,
+			true,
+			0,
+			-1,
+			0b00010010, // 18
 		},
 	}
 	for _, test := range tests {
@@ -129,6 +167,10 @@ func TestPaneCoder(t *testing.T) {
 			if err != nil {
 				t.Fatalf("failed to encode pane %v, got %v", input, err)
 			}
+			first := buf.Bytes()[0]
+			if got, want := first, test.firstByte; got != want {
+				t.Errorf("Unexpected First Byte: got %#08b, want %#08b, for %v ", got, want, input)
+			}
 			got, err := DecodePane(&buf)
 			if err != nil {
 				t.Fatalf("failed to decode pane from buffer %v, got %v", &buf, err)

sdks/go/pkg/beam/core/graph/window/trigger/trigger.go

@@ -352,7 +352,7 @@ func (t *NeverTrigger) String() string {
 func (t NeverTrigger) trigger() {}
 
 // Never creates a Never Trigger that is never ready to fire.
-// There will only be an ON_TIME output and a final output at window expiration.
+// There will only be a single ON_TIME final output at window expiration + allowed lateness.
 func Never() *NeverTrigger {
 	return &NeverTrigger{}
 }

sdks/go/pkg/beam/core/typex/special.go

@@ -98,6 +98,19 @@ const (
 	PaneUnknown PaneTiming = 3
 )
 
+func (t PaneTiming) String() string {
+	switch t {
+	case PaneEarly:
+		return "early"
+	case PaneOnTime:
+		return "ontime"
+	case PaneLate:
+		return "late"
+	default:
+		return "unknown"
+	}
+}
+
 // PaneInfo represents the output pane.
 type PaneInfo struct {
 	Timing                     PaneTiming