Github user StephanEwen commented on the pull request: https://github.com/apache/flink/pull/917#issuecomment-123720593 The mechanism looks good, all in all. Some comments: - I think it makes the code more understandable, if the `decorateMessage()` method would be called something like `attachSession()`, or so. Is the decoration used - We have decided to gradually transition the runtime to Java, as this mixture of languages is making it very clumsy in many parts. All other changes followed the pattern to add new classes only in Java. Are there principle reasons to not do this here as well? Especially by adding classes that are at the core of this new mechanism (like `RequiresLeaderSessionID`) in Scala, we effectively cement this language blend. - In prior refactoring, we changed it such that JobManager, TaskManager, etc do not use mixins any more. A big part of the decision were "clean logs" and Java interoperability. This patch reverts this effort. Is there any principle reason for that?
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