Hi, Tianzi, a coworker of mine, was trying out a streaming Java pipeline. It's reading from Pub/Sub, doing fixed sized windows, doing an aggregation like a GroupByKey or Sum, and then trying to print the elements in each window. But it's not showing anything.
The pipeline is basically this: Pub/Sub > FixedWindows > WithKeys > GroupByKey > Map(print) Curiously, removing the GroupByKey (or any other aggregation), works as expected. I know for sure this works in Python, so it seems a little odd it doesn't work in Java. We spent over an hour yesterday trying to find what was happening and couldn't find anything. We're tracking this in [BEAM-12975 <https://issues.apache.org/jira/browse/BEAM-12075>], with the code to reproduce the issue.
