Hi Dongwon, I think you understand it correctly. You can find this logic here[1]
[1] https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/streamstatus/StatusWatermarkValve.java#L108 Dongwon Kim <eastcirc...@gmail.com> 于2020年12月10日周四 上午12:21写道： > Hi, > > Let's consider two operators: A (parallelism=2) and B (parallelism=1). > B has two input partitions, B_A1 and B_A2, which are connected to A1 and > A2 respectively. > > At some point, > - B_A1's watermark : 12 > - B_A2's watermark : 10 > - B's event-time clock : 10 = min(12, 10) > - B has registered a timer at 12 > - No data will be fed into the pipeline for the next few hours, but I want > the timer to be fired after a few seconds if no data is coming. > > After adopting a watermark strategy explained in [1], I found that the > timer is fired as wished! That's awesome! > > But I want to know what happens inside in detail. > Based on my current understanding of how watermark is calculated [2], I > cannot come up with what happens inside when idleness is considered. > If B_A2 is marked idle earlier than B_A1, is B's event-time clock > calculated as min(12, MAX_WATERMARK)? > > Thanks, > > Dongwon > > [1] > https://ci.apache.org/projects/flink/flink-docs-stable/dev/event_timestamps_watermarks.html#dealing-with-idle-sources > [2] > https://ci.apache.org/projects/flink/flink-docs-stable/dev/event_timestamps_watermarks.html#how-operators-process-watermarks > [3] > https://cwiki.apache.org/confluence/display/FLINK/FLIP-126%3A+Unify+%28and+separate%29+Watermark+Assigners > -- Best, Benchao Li
