Hi Matin, We run a mix of JDK8/11/17/25 on our in-house version of Flink 1.11/1.17, and is planning to migrate to JDK25 as the major runtime JDK version. We still compile Flink and most of the user jars with JDK8 for compatibility issues though, but is willing to swtich to a new one when we migrate to a new Flink version.
Currently, supporting a new runtime JDK and a new compile JDK and mixed together. I'd recommand we treating the two as separate tasks, and prioritizing support for running on new versions of JDK to get the free performance boost. For compile-time JDK and lanaguage levels, it's better not to be too aggresive or we may prevent a large number of users from upgrading, JDK17 may be a good starting point. For new language features, we hope to see how virtual threads could be integrated in Flink for easier async IO development at a low memory cost. Best, Zhanghao Chen ________________________________ From: Martijn Visser <[email protected]> Sent: Saturday, October 31, 2026 2:23 To: dev <[email protected]>; user <[email protected]> Subject: [DISCUSS] Which Java versions are you running Flink on? Hi everyone, I’m planning to write a FLIP about which Java versions Flink should support going forward. Before I do, I’d like to understand how you actually run Flink today. Could you reply with as much of the following as you're comfortable sharing? 1. Which Flink version(s) do you run in production? 2. Which Java version runs your Flink cluster (JobManager/TaskManager)? 3. Which Java version do you use to compile your jobs, and which language level do you target? 4. How do you deploy Flink: official Docker images, your own images, a managed/vendor service, or something else? 5. Do you plan to move to a newer Java version in the next 12 months? If not, what's stopping you (dependencies, platform constraints, company policy, ...)? 6. Are there features in newer Java releases you'd like Flink to use or support? Partial answers help too. A single line like "Flink 1.20, Java 11, own Docker images, no upgrade planned because of X" is already valuable. I’ll use your responses to make sure the proposal reflects how Flink users run Java today and where you’re heading. Nothing has been decided yet: the FLIP itself will be discussed on the dev list, and any change to the supported versions will be announced well in advance. Thanks in advance! Best regards, Martijn
