#202 parallelizes batch rocessing

collector.go

@@ -39,4 +39,37 @@ var (
 		labelStreamName,
 		labelShardID,
 	})
+
+	gaugeBatchSize = prometheus.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace:   "net",
+		Subsystem:   "kinesis",
+		Name:        "get_records_result_size",
+		Help:        "number of records received from a call to get results",
+		ConstLabels: nil,
+	}, []string{
+		labelStreamName,
+		labelShardID,
+	})
+
+	histogramBatchDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "net",
+		Subsystem: "kinesis",
+		Name:      "records_processing_duration",
+		Help:      "time in seconds it takes to process all of the records that were returned from a get records call",
+		Buckets:   []float64{0.1, 0.5, 1, 3, 5, 10, 30, 60},
+	}, []string{
+		labelStreamName,
+		labelShardID,
+	})
+
+	histogramAverageRecordDuration = prometheus.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "net",
+		Subsystem: "kinesis",
+		Name:      "average_record_processing_duration",
+		Help:      "average time in seconds it takes to process a single record in a batch",
+		Buckets:   []float64{0.003, 0.005, 0.01, 0.025, 0.05, 0.1, 1, 3},
+	}, []string{
+		labelStreamName,
+		labelShardID,
+	})
 )

consumer.go

@@ -70,6 +70,9 @@ func New(streamName string, opts ...Option) (*Consumer, error) {
 		errs = errors.Join(errs, c.metricRegistry.Register(collectorMillisBehindLatest))
 		errs = errors.Join(errs, c.metricRegistry.Register(counterEventsConsumed))
 		errs = errors.Join(errs, c.metricRegistry.Register(counterCheckpointsWritten))
+		errs = errors.Join(errs, c.metricRegistry.Register(gaugeBatchSize))
+		errs = errors.Join(errs, c.metricRegistry.Register(histogramBatchDuration))
+		errs = errors.Join(errs, c.metricRegistry.Register(histogramAverageRecordDuration))
 		if errs != nil {
 			return nil, errs
 		}
@@ -95,7 +98,7 @@ type Consumer struct {
 	isAggregated       bool
 	shardClosedHandler ShardClosedHandler
 	numWorkers         int
-	workerPool         WorkerPool
+	workerPool         *WorkerPool
 }
 
 // ScanFunc is the type of the function called for each message read
@@ -157,9 +160,9 @@ func (c *Consumer) Scan(ctx context.Context, fn ScanFunc) error {
 // ScanShard loops over records on a specific shard, calls the callback func
 // for each record and checkpoints the progress of scan.
 func (c *Consumer) ScanShard(ctx context.Context, shardID string, fn ScanFunc) error {
-	wp := NewWorkerPool(c.streamName, c.numWorkers, fn)
+	c.workerPool = NewWorkerPool(c.streamName, c.numWorkers, fn)
-	wp.Start(ctx)
+	c.workerPool.Start(ctx)
-	defer wp.Stop()
+	defer c.workerPool.Stop()
 
 	// get last seq number from checkpoint
 	lastSeqNum, err := c.group.GetCheckpoint(ctx, c.streamName, shardID)
@@ -200,55 +203,10 @@ func (c *Consumer) ScanShard(ctx context.Context, shardID string, fn ScanFunc) e
 				return fmt.Errorf("get shard iterator error: %w", err)
 			}
 		} else {
-			// loop over records, call callback func
+			lastSeqNum, err = c.processRecords(ctx, shardID, resp)
-			var records []types.Record
-
-			// desegregate records
-			if c.isAggregated {
-				records, err = disaggregateRecords(resp.Records)
 			if err != nil {
 				return err
 			}
-			} else {
-				records = resp.Records
-			}
-
-			for _, r := range records {
-				select {
-				case <-ctx.Done():
-					return nil
-				default:
-					record := Record{r, shardID, resp.MillisBehindLatest}
-					wp.Submit(record)
-
-					res := wp.Result()
-					var err error
-					if res != nil && res.Err != nil {
-						err = res.Err
-					}
-
-					secondsBehindLatest := float64(time.Duration(*resp.MillisBehindLatest)*time.Millisecond) / float64(time.Second)
-					collectorMillisBehindLatest.
-						With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).
-						Observe(secondsBehindLatest)
-
-					if err != nil && !errors.Is(err, ErrSkipCheckpoint) {
-						return err
-					}
-
-					if !errors.Is(err, ErrSkipCheckpoint) {
-						if err := c.group.SetCheckpoint(ctx, c.streamName, shardID, *r.SequenceNumber); err != nil {
-							return err
-						}
-						c.counter.Add("checkpoint", 1)
-						counterCheckpointsWritten.With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).Inc()
-					}
-
-					counterEventsConsumed.With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).Inc()
-					c.counter.Add("records", 1)
-					lastSeqNum = *r.SequenceNumber
-				}
-			}
 
 			if isShardClosed(resp.NextShardIterator, shardIterator) {
 				c.logger.DebugContext(ctx, "shard closed", slog.String("shard-id", shardID))
@@ -276,6 +234,104 @@ func (c *Consumer) ScanShard(ctx context.Context, shardID string, fn ScanFunc) e
 	}
 }
 
+func (c *Consumer) processRecords(ctx context.Context, shardID string, resp *kinesis.GetRecordsOutput) (string, error) {
+	if len(resp.Records) == 0 {
+		return "", nil
+	}
+
+	startedAt := time.Now()
+	batchSize := float64(len(resp.Records))
+	gaugeBatchSize.
+		With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).
+		Set(batchSize)
+
+	secondsBehindLatest := float64(time.Duration(*resp.MillisBehindLatest)*time.Millisecond) / float64(time.Second)
+	collectorMillisBehindLatest.
+		With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).
+		Observe(secondsBehindLatest)
+
+	// loop over records, call callback func
+	var records []types.Record
+
+	// disaggregate records
+	var err error
+	if c.isAggregated {
+		records, err = disaggregateRecords(resp.Records)
+		if err != nil {
+			return "", err
+		}
+	} else {
+		records = resp.Records
+	}
+
+	if len(records) == 0 {
+		// nothing to do here
+		return "", nil
+	}
+
+	// submit in goroutine
+	go func() {
+		for _, r := range records {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				record := Record{r, shardID, resp.MillisBehindLatest}
+				// blocks until someone is ready to pick it up
+				c.workerPool.Submit(record)
+			}
+		}
+	}()
+
+	// wait for all tasks to be processed
+	numberOfProcessedTasks := 0
+	timeout := 5 * time.Second
+	countDownTimer := time.NewTimer(timeout)
+	for {
+		if numberOfProcessedTasks == len(records) {
+			break
+		}
+		select {
+		case <-ctx.Done():
+			return "", nil
+		case <-countDownTimer.C:
+			return "", fmt.Errorf("timeline exceeded while awaiting result from workers")
+		default:
+			res, err := c.workerPool.Result()
+			if err != nil && !errors.Is(err, ErrSkipCheckpoint) {
+				return "", err // TODO make it more clever once :)
+			}
+			if errors.Is(err, ErrSkipCheckpoint) || res != nil {
+				numberOfProcessedTasks++
+				countDownTimer.Reset(timeout)
+
+				counterEventsConsumed.With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).Inc()
+				c.counter.Add("records", 1)
+			}
+		}
+	}
+
+	// we MUST only reach this point if everything is processed
+	lastSeqNum := *records[len(records)-1].SequenceNumber
+
+	if err := c.group.SetCheckpoint(ctx, c.streamName, shardID, lastSeqNum); err != nil {
+		return "", fmt.Errorf("set checkpoint error: %w", err)
+	}
+	c.counter.Add("checkpoint", int64(numberOfProcessedTasks))
+	counterCheckpointsWritten.
+		With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).
+		Add(float64(numberOfProcessedTasks))
+
+	duration := time.Since(startedAt).Seconds()
+	histogramBatchDuration.
+		With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).
+		Observe(duration)
+	histogramAverageRecordDuration.
+		With(prometheus.Labels{labelStreamName: c.streamName, labelShardID: shardID}).
+		Observe(duration / batchSize)
+	return lastSeqNum, nil
+}
+
 // temporary conversion func of []types.Record -> DesegregateRecords([]*types.Record) -> []types.Record
 func disaggregateRecords(in []types.Record) ([]types.Record, error) {
 	var recs []types.Record

consumer_test.go

@@ -41,6 +41,7 @@ func TestScan(t *testing.T) {
 			return &kinesis.GetRecordsOutput{
 				NextShardIterator:  nil,
 				Records:            records,
+				MillisBehindLatest: aws.Int64(int64(1000)),
 			}, nil
 		},
 		listShardsMock: func(_ context.Context, _ *kinesis.ListShardsInput, _ ...func(*kinesis.Options)) (*kinesis.ListShardsOutput, error) {
@@ -92,7 +93,7 @@ func TestScan(t *testing.T) {
 		t.Errorf("counter error expected %d, got %d", 2, val)
 	}
 
-	val, err := cp.GetCheckpoint("myStreamName", "myShard")
+	val, err := cp.GetCheckpoint(ctx, "myStreamName", "myShard")
 	if err != nil && val != "lastSeqNum" {
 		t.Errorf("checkout error expected %s, got %s", "lastSeqNum", val)
 	}
@@ -158,7 +159,7 @@ func TestScanShard(t *testing.T) {
 	}
 
 	// sets checkpoint
-	val, err := cp.GetCheckpoint("myStreamName", "myShard")
+	val, err := cp.GetCheckpoint(ctx, "myStreamName", "myShard")
 	if err != nil && val != "lastSeqNum" {
 		t.Fatalf("checkout error expected %s, got %s", "lastSeqNum", val)
 	}
@@ -242,7 +243,7 @@ func TestScanShard_SkipCheckpoint(t *testing.T) {
 		t.Fatalf("scan shard error: %v", err)
 	}
 
-	val, err := cp.GetCheckpoint("myStreamName", "myShard")
+	val, err := cp.GetCheckpoint(ctx, "myStreamName", "myShard")
 	if err != nil && val != "firstSeqNum" {
 		t.Fatalf("checkout error expected %s, got %s", "firstSeqNum", val)
 	}

worker.go

@@ -10,7 +10,7 @@ import (
 type Result struct {
 	Record
 	WorkerName string
-	Err        error
+	err        error
 }
 
 // WorkerPool allows to parallel process records
@@ -55,12 +55,12 @@ func (wp *WorkerPool) Submit(r Record) {
 }
 
 // Result returns the Result of the Submit-ed Record after it has been processed.
-func (wp *WorkerPool) Result() *Result {
+func (wp *WorkerPool) Result() (Result, error) {
 	select {
 	case r := <-wp.resultC:
-		return &r
+		return r, r.err
 	default:
-		return nil
+		return Result{}, nil
 	}
 }
 
@@ -91,7 +91,7 @@ func (w *worker) start(ctx context.Context) {
 				res := Result{
 					Record:     r,
 					WorkerName: w.name,
-					Err:        err,
+					err:        err,
 				}
 
 				w.resultC <- res