Hi Gyula, Thanks for bringing up this topic! Kryo incompatibility with newer Java versions is a major issue that needs to be addressed, and in my opinion, Flink 2.0 provides a great opportunity to introduce this change.
My understanding is that state compatibility was not a strict goal during 2.0 development. However, I’ve heard mentions that it might actually be compatible after all. >From this perspective: definitely +1 on upgrading Kryo. The decision to invest additional effort in maintaining compatibility should depend on whether all other changes have preserved compatibility guarantees. If Kryo is the only breaking change, then ensuring compatibility might be worth considering. Best, Alex On Fri, 21 Feb 2025 at 06:05, Gyula Fóra <gyula.f...@gmail.com> wrote: > > 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
