[#22737] Fit & Finish for Go SDK timer support.

sdks/go/examples/timer_wordcap/wordcap.go

@@ -21,15 +21,12 @@
 package main
 
 import (
-	"bytes"
 	"context"
-	"encoding/binary"
 	"flag"
 	"fmt"
 	"time"
 
 	"github.com/apache/beam/sdks/v2/go/pkg/beam"
-	"github.com/apache/beam/sdks/v2/go/pkg/beam/core/graph/mtime"
 	"github.com/apache/beam/sdks/v2/go/pkg/beam/core/state"
 	"github.com/apache/beam/sdks/v2/go/pkg/beam/core/timers"
 	"github.com/apache/beam/sdks/v2/go/pkg/beam/log"
@@ -62,21 +59,7 @@ func NewStateful() *Stateful {
 	}
 }
 
-func (s *Stateful) OnTimer(ctx context.Context, ts beam.EventTime, tp timers.Provider, key, timerKey, timerTag string, emit func(string, string)) {
-	switch timerKey {
-	case "outputState":
-		log.Infof(ctx, "Timer outputState fired on stateful for element: %v.", key)
-		s.OutputState.Set(tp, ts.ToTime().Add(5*time.Second), timers.WithTag("1"))
-		switch timerTag {
-		case "1":
-			s.OutputState.Clear(tp)
-			log.Infof(ctx, "Timer with tag 1 fired on outputState stateful DoFn.")
-			emit(timerKey, timerTag)
-		}
-	}
-}
-
-func (s *Stateful) ProcessElement(ctx context.Context, ts beam.EventTime, sp state.Provider, tp timers.Provider, key, word string, emit func(string, string)) error {
+func (s *Stateful) ProcessElement(ctx context.Context, ts beam.EventTime, sp state.Provider, tp timers.Provider, key, word string, _ func(beam.EventTime, string, string)) error {
 	s.ElementBag.Add(sp, word)
 	s.MinTime.Add(sp, int64(ts))
 
@@ -85,23 +68,77 @@ func (s *Stateful) ProcessElement(ctx context.Context, ts beam.EventTime, sp sta
 		return err
 	}
 	if !ok {
-		toFire = int64(mtime.Now().Add(1 * time.Minute))
+		toFire = int64(time.Now().Add(30 * time.Second).UnixMilli())
 	}
 	minTime, _, err := s.MinTime.Read(sp)
 	if err != nil {
 		return err
 	}
 
-	s.OutputState.Set(tp, time.UnixMilli(toFire), timers.WithOutputTimestamp(time.UnixMilli(minTime)), timers.WithTag(word))
+	s.OutputState.Set(tp, time.UnixMilli(toFire), timers.WithOutputTimestamp(time.UnixMilli(minTime)))
+	// A timer can be set with independent to fire with independant string tags.
+	s.OutputState.Set(tp, time.UnixMilli(toFire), timers.WithTag(word), timers.WithOutputTimestamp(time.UnixMilli(minTime)))
 	s.TimerTime.Write(sp, toFire)
-
 	return nil
 }
 
+func (s *Stateful) OnTimer(ctx context.Context, ts beam.EventTime, sp state.Provider, tp timers.Provider, key string, timer timers.Context, emit func(beam.EventTime, string, string)) {
+	log.Infof(ctx, "Timer fired for key %q, for family %q and tag %q", key, timer.Family, timer.Tag)
+
+	const tag = "emit" // Tags can be arbitrary strings, but we're associating behavior with this tag in this method.
+
+	// Check which timer has fired.
+	switch timer.Family {
+	case s.OutputState.Family:
+		switch timer.Tag {
+		case "":
+			// Timers can be set within the OnTimer method.
+			// In this case the emit tag timer to fire in 5 seconds.
+			s.OutputState.Set(tp, ts.ToTime().Add(5*time.Second), timers.WithTag(tag))
+		case tag:
+			// When the emit tag fires, read the batched data.
+			es, ok, err := s.ElementBag.Read(sp)
+			if err != nil {
+				log.Errorf(ctx, "error reading ElementBag: %v", err)
+				return
+			}
+			if !ok {
+				log.Infof(ctx, "No elements in bag.")
+				return
+			}
+			minTime, _, err := s.MinTime.Read(sp)
+			if err != nil {
+				log.Errorf(ctx, "error reading ElementBag: %v", err)
+				return
+			}
+			log.Infof(ctx, "Emitting %d elements", len(es))
+			for _, word := range es {
+				emit(beam.EventTime(minTime), key, word)
+			}
+			// Clean up the state that has been evicted.
+			s.ElementBag.Clear(sp)
+			s.MinTime.Clear(sp)
+			s.OutputState.ClearTag(tp, tag) // Clean up the fired timer tag. (Temporary workaround for a runner bug.)
+		}
+	}
+}
+
 func init() {
-	register.DoFn7x1[context.Context, beam.EventTime, state.Provider, timers.Provider, string, string, func(string, string), error](&Stateful{})
-	register.Emitter2[string, string]()
+	register.DoFn7x1[context.Context, beam.EventTime, state.Provider, timers.Provider, string, string, func(beam.EventTime, string, string), error](&Stateful{})
+	register.Emitter3[beam.EventTime, string, string]()
 	register.Emitter2[beam.EventTime, int64]()
+	register.Function1x2(toKeyedString)
+}
+
+func generateSequence(s beam.Scope, now time.Time, duration, interval time.Duration) beam.PCollection {
+	s = s.Scope("generateSequence")
+	def := beam.Create(s, periodic.NewSequenceDefinition(now, now.Add(duration), interval))
+	seq := periodic.Sequence(s, def)
+	return seq
+}
+
+func toKeyedString(b int64) (string, string) {
+	return "test", fmt.Sprintf("%03d", b)
 }
 
 func main() {
@@ -110,26 +147,11 @@ func main() {
 
 	ctx := context.Background()
 
-	p := beam.NewPipeline()
-	s := p.Root()
-
-	out := periodic.Impulse(s, time.Now(), time.Now().Add(5*time.Minute), 5*time.Second, true)
-
-	intOut := beam.ParDo(s, func(b []byte) int64 {
-		var val int64
-		buf := bytes.NewReader(b)
-		binary.Read(buf, binary.BigEndian, &val)
-		return val
-	}, out)
-
-	str := beam.ParDo(s, func(b int64) string {
-		return fmt.Sprintf("%03d", b)
-	}, intOut)
+	p, s := beam.NewPipelineWithRoot()
 
-	keyed := beam.ParDo(s, func(ctx context.Context, ts beam.EventTime, s string) (string, string) {
-		return "test", s
-	}, str)
+	out := generateSequence(s, time.Now(), 1*time.Minute, 5*time.Second)
 
+	keyed := beam.ParDo(s, toKeyedString, out)
 	timed := beam.ParDo(s, NewStateful(), keyed)
 	debug.Printf(s, "post stateful: %v", timed)
 

sdks/go/pkg/beam/core/graph/edge.go

@@ -156,7 +156,6 @@ type MultiEdge struct {
 	DoFn             *DoFn                   // ParDo
 	RestrictionCoder *coder.Coder            // SplittableParDo
 	StateCoders      map[string]*coder.Coder // Stateful ParDo
-	TimerCoders      *coder.Coder            // Stateful ParDo
 	CombineFn        *CombineFn              // Combine
 	AccumCoder       *coder.Coder            // Combine
 	Value            []byte                  // Impulse

sdks/go/pkg/beam/core/runtime/exec/coder.go

@@ -1228,8 +1228,7 @@ func EncodeWindowedValueHeader(enc WindowEncoder, ws []typex.Window, t typex.Eve
 	if err := enc.Encode(ws, w); err != nil {
 		return err
 	}
-	err := coder.EncodePane(p, w)
-	return err
+	return coder.EncodePane(p, w)
 }
 
 // DecodeWindowedValueHeader deserializes a windowed value header.
@@ -1257,49 +1256,61 @@ func DecodeWindowedValueHeader(dec WindowDecoder, r io.Reader) ([]typex.Window,
 }
 
 // encodeTimer encodes a TimerRecv into a byte stream.
+// Avoids partial writes to provided writer on encoding errors.
 func encodeTimer(elm ElementEncoder, win WindowEncoder, tm TimerRecv, w io.Writer) error {
 	var b bytes.Buffer
 	err := elm.Encode(tm.Key, &b)
 	if err != nil {
 		return errors.WithContext(err, "error encoding key")
 	}
 
-	if err := coder.EncodeStringUTF8(tm.Tag, &b); err != nil {
+	if err := encodeTimerSuffix(win, tm, &b); err != nil {
+		return err
+	}
+	w.Write(b.Bytes())
+
+	return nil
+}
+
+// encodeTimerSuffix enccodes the timer directly to the provided writer.
+func encodeTimerSuffix(win WindowEncoder, tm TimerRecv, w io.Writer) error {
+	if err := coder.EncodeStringUTF8(tm.Tag, w); err != nil {
 		return errors.WithContext(err, "error encoding tag")
 	}
 
-	if err := win.Encode(tm.Windows, &b); err != nil {
+	if err := win.Encode(tm.Windows, w); err != nil {
 		return errors.WithContext(err, "error encoding window")
 	}
 
-	if err := coder.EncodeBool(tm.Clear, &b); err != nil {
+	if err := coder.EncodeBool(tm.Clear, w); err != nil {
 		return errors.WithContext(err, "error encoding clear bit")
 	}
 
 	if !tm.Clear {
-		if err := coder.EncodeEventTime(tm.FireTimestamp, &b); err != nil {
+		if err := coder.EncodeEventTime(tm.FireTimestamp, w); err != nil {
 			return errors.WithContext(err, "error encoding fire timestamp")
 		}
-		if err := coder.EncodeEventTime(tm.HoldTimestamp, &b); err != nil {
+		if err := coder.EncodeEventTime(tm.HoldTimestamp, w); err != nil {
 			return errors.WithContext(err, "error encoding hold timestamp")
 		}
-		if err := coder.EncodePane(tm.Pane, &b); err != nil {
+		if err := coder.EncodePane(tm.Pane, w); err != nil {
 			return errors.WithContext(err, "error encoding paneinfo")
 		}
 	}
-	w.Write(b.Bytes())
-
 	return nil
 }
 
 // decodeTimer decodes timer byte encoded with standard timer coder spec.
 func decodeTimer(dec ElementDecoder, win WindowDecoder, r io.Reader) (TimerRecv, error) {
 	tm := TimerRecv{}
-	key, err := dec.Decode(r)
+	var keyBuf bytes.Buffer
+	tr := io.TeeReader(r, &keyBuf)
+	key, err := dec.Decode(tr)
 	if err != nil {
 		return tm, errors.WithContext(err, "error decoding key")
 	}
 	tm.Key = key
+	tm.KeyString = keyBuf.String()
 
 	s, err := coder.DecodeStringUTF8(r)
 	if err != nil && err != io.EOF {

sdks/go/pkg/beam/core/runtime/exec/datasource.go

@@ -263,10 +263,8 @@ func (n *DataSource) Process(ctx context.Context) ([]*Checkpoint, error) {
 		}
 	},
 		func(bcr *byteCountReader, ptransformID, timerFamilyID string) error {
-
-			if fn, ok := n.OnTimerTransforms[ptransformID].Fn.OnTimerFn(); ok {
-				_, err := n.OnTimerTransforms[ptransformID].InvokeTimerFn(ctx, fn, timerFamilyID, bcr)
-				if err != nil {
+			if node, ok := n.OnTimerTransforms[ptransformID]; ok {
+				if err := node.ProcessTimers(timerFamilyID, bcr); err != nil {
 					log.Warnf(ctx, "expected transform %v to have an OnTimer method attached to handle"+
 						"Timer Family ID: %v callback, but it did not. Please file an issue with Apache Beam"+
 						"if you have defined OnTimer method with reproducible code at https://github.com/apache/beam/issues", ptransformID, timerFamilyID)

sdks/go/pkg/beam/core/runtime/exec/datasource_test.go

@@ -16,6 +16,7 @@
 package exec
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"io"
@@ -1020,6 +1021,8 @@ func runOnRoots(ctx context.Context, t *testing.T, p *Plan, name string, mthd fu
 
 type TestDataManager struct {
 	Ch chan Elements
+
+	TimerWrites map[string]*bytes.Buffer
 }
 
 func (dm *TestDataManager) OpenElementChan(ctx context.Context, id StreamID, expectedTimerTransforms []string) (<-chan Elements, error) {
@@ -1031,9 +1034,27 @@ func (dm *TestDataManager) OpenWrite(ctx context.Context, id StreamID) (io.Write
 }
 
 func (dm *TestDataManager) OpenTimerWrite(ctx context.Context, id StreamID, family string) (io.WriteCloser, error) {
-	return nil, nil
+	if dm.TimerWrites == nil {
+		dm.TimerWrites = map[string]*bytes.Buffer{}
+	}
+	buf, ok := dm.TimerWrites[family]
+	if !ok {
+		buf = &bytes.Buffer{}
+		dm.TimerWrites[family] = buf
+	}
+	return struct {
+		*bytes.Buffer
+		io.Closer
+	}{
+		Buffer: buf,
+		Closer: noopCloser{},
+	}, nil
 }
 
+type noopCloser struct{}
+
+func (noopCloser) Close() error { return nil }
+
 type chanWriter struct {
 	Ch  chan Elements
 	Buf []byte

sdks/go/pkg/beam/core/runtime/exec/fn.go

@@ -87,7 +87,7 @@ type InvokeOpts struct {
 	we    sdf.WatermarkEstimator
 	sa    UserStateAdapter
 	sr    StateReader
-	ta    UserTimerAdapter
+	ta    *userTimerAdapter
 	tm    DataManager
 	extra []any
 }
@@ -242,11 +242,7 @@ func (n *invoker) invokeWithOpts(ctx context.Context, pn typex.PaneInfo, ws []ty
 	}
 
 	if n.tpIdx >= 0 {
-		tp, err := opts.ta.NewTimerProvider(ctx, opts.tm, ts, ws, opts.opt)
-		if err != nil {
-			return nil, err
-		}
-		n.tp = &tp
+		n.tp = opts.ta.NewTimerProvider(pn, ws)
 		args[n.tpIdx] = n.tp
 	}