Use Java 11 about docker-flink

[patricklucas]

Thanks. I'm going to close this for now, but upgrading these images will be a priority for any later Java support from Flink whenever that occurs, so a new issue can be opened at that time.

[patricklucas]

Java 8 is used because Flink itself still depends on Java 8. When newer Java becomes supported by Flink, we'll update these images.

FLINK-8033 tracks support for Java 9, and is targeted for Flink 1.7.0 which should be released pretty soon. I can't find an issue for Java 11 support, but I imagine it will be added to the roadmap once Java 9 support is finalized.

[SMadani]

Java 9 has been end of life since March, I'm not sure why anyone would want to support it. The "support path" should be quite clear: Java 11 then Java 15.

[patricklucas]

You should be taking this up with the Flink community on the mailing list or issue tracker, not the Dockerfile repo.

Nevertheless, supporting Java 9 is a necessary step on the way to current Java support—it would be difficult to support Java 11 before it works on Java 9—and this work alone has been quite involved and ongoing since long before either Java 10 or Java 11 were released.

[SMadani]

I've raised the issue on JIRA. Also my point was that supporting Java 11 should require no extra work if supporting Java 9, it's basically a version change so it makes no sense to call it "Java 9" support when Java 9 practically doesn't exist anymore.