Hi Gyula, Thanks for bringing this up! Definitely +1 for upgrading Kryo in Flink 2.0. As a side note, it might be useful to introduce customizable generic serializer support like Spark, where you can switch to your own serializer via the "spark.serializer" [1] option. Users starting new applications can introduce their own serialization stack in this case to resolve Java compatibility issue is this case or for other performance issues.
[1] https://spark.apache.org/docs/latest/configuration.html Best, Zhanghao Chen ________________________________ From: Gyula F?ra <gyula.f...@gmail.com> Sent: Friday, February 21, 2025 14:04 To: dev <dev@flink.apache.org> Subject: [DISCUSSION] Upgrade to Kryo 5 for Flink 2.0 Hey all! I would like to rekindle this discussion as it seems that it has stalled several times in the past and we are nearing the point in time where the decision has to be made with regards to 2.0. (we are already a bit late but nevermind) There has been numerous requests and efforts to upgrade Kryo to better support newer Java versions and Java native types. I think we can all agree that this change is inevitable one way or another. The latest JIRA for this seems to be: https://issues.apache.org/jira/browse/FLINK-3154 There is even an open PR that accomplishes this (currently in a state incompatible way) but based on the discussion it seems that with some extra complexity compatibility can even be preserved by having both the old and new Kryo versions active at the same time. The main question here is whether state compatibility is important for 2.0 with this regard or we want to bite the bullet and make this upgrade once and for all. Cheers, Gyula
