lukecwik commented on pull request #12603: URL: https://github.com/apache/beam/pull/12603#issuecomment-702422068
> The phenomenon of microbatches producing results early I noticed it too in the past when trying to enable the Read.Unbounded tests. I could not understand why, and I thought it was probably due to some glitch in Spark implementation or us screwing their scheduling but I struggled to debug the issue properly. > > > Since watermark holds don't seem to be implemented, does the GroupAlsoViaWindowSet hold back the watermark for elements that it currently has buffered? > > Probably, at least that may explain some of the inconsistencies. The Java based trigger implementation relies on this to produce correct results. Implementing this would like enable a bunch of streaming use cases. > > Can you explain how the GlobalWatermarkHolder works, can I register anything as a sourceId? > > In all honesty I am not so familiar with watermark handling on the Spark runner. I took a look at the GlobalWatermarkHolder class and tried to figure out but it was not really evident. > > My impression is that the sourceId is aligned somehow with Spark's assigned streamId, but I might be misinterpreting it. > https://github.com/apache/spark/blob/13664434387e338a5029e73a4388943f34e3fc07/streaming/src/main/scala/org/apache/spark/streaming/scheduler/InputInfoTracker.scala#L30 > > I wish I could help more but that part of the code is also not so well documented. I doubt that the original authors of the code still remember the details but maybe they remember at least the intentions of `GlobalWatermarkHolder` and its use, and maybe if there were any open issues. Just in case 🤞 maybe: @amitsela @aviemzur @staslev That would be great if someone could give guidance here. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
