Github user manuzhang commented on a diff in the pull request: https://github.com/apache/incubator-gearpump/pull/227#discussion_r147025062 --- Diff: streaming/src/main/scala/org/apache/gearpump/streaming/dsl/task/GroupByTask.scala --- @@ -27,15 +27,15 @@ import org.apache.gearpump.cluster.UserConfig import org.apache.gearpump.streaming.Constants.{GEARPUMP_STREAMING_GROUPBY_FUNCTION, GEARPUMP_STREAMING_OPERATOR} import org.apache.gearpump.streaming.dsl.window.impl.{TimestampedValue, WindowRunner} import org.apache.gearpump.streaming.source.Watermark -import org.apache.gearpump.streaming.task.{Task, TaskContext, TaskUtil} +import org.apache.gearpump.streaming.task.{Task, TaskContext, TaskUtil, WatermarkProducer} /** * Processes messages in groups as defined by groupBy function. */ class GroupByTask[IN, GROUP, OUT]( groupBy: IN => GROUP, taskContext: TaskContext, - userConfig: UserConfig) extends Task(taskContext, userConfig) { + userConfig: UserConfig) extends Task(taskContext, userConfig) with WatermarkProducer { --- End diff -- And only `GroupByTask` ?
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