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package operator
import (
"context"
"goflink/core"
)
// TimestampAssigner is responsible for event time defined by user
type TimestampAssigner[IN any] func(in IN) int64
type WaterGeneratorOperator[IN any] struct {
assigner TimestampAssigner[IN]
maxOutOfOrder int64
currentMaxTimestamp int64
lastEmittedWatermark int64
}
func NewWatermarkGeneratorOperator[IN any](maxOutOfOrder int64, assigner TimestampAssigner[IN]) *WaterGeneratorOperator[IN] {
return &WaterGeneratorOperator[IN]{
maxOutOfOrder: maxOutOfOrder,
assigner: assigner,
lastEmittedWatermark: -1,
}
}
func (w *WaterGeneratorOperator[IN]) Open(ctx context.Context) error {
return nil
}
func (w *WaterGeneratorOperator[IN]) Process(ctx context.Context, record core.StreamRecord[IN], out Emitter[IN]) error {
if record.Type == core.RecordData {
// query the time
eventTime := w.assigner(record.Value)
record.Timestamp = eventTime
// update the max timestamp
if w.currentMaxTimestamp < eventTime {
w.currentMaxTimestamp = eventTime
}
// calc the watermark
watermark := w.currentMaxTimestamp - w.maxOutOfOrder
// check if current watermark later than previous watermark
if watermark > w.lastEmittedWatermark {
w.lastEmittedWatermark = watermark
return out.Emit(ctx, core.NewWatermarkRecord[IN](watermark))
}
return nil
}
return out.Emit(ctx, record)
}
func (w *WaterGeneratorOperator[IN]) Close(ctx context.Context) error {
return nil
}
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