Hi all! We have a problem in the *DataStream API* around Windows for *CoGroup* and *Join*. These operations currently do not allow to set a parallelism, which is a pretty heavy problem.
To fix it properly, we need to change the return types of the coGroup() and join() operations, which *breaks the binary compatibility* - it* retains source compatibility*, though. The pull request with the change is: https://github.com/apache/flink/pull/2305 There are very clumsy ways to work around this (custom casts in the user code or making the join() / coGroup() behave differently than the other operators) which we did not really think of as viable, because they would need to be changed again in the future once we pull the API straight (breaking even source compatibility then). *I would suggest to actually break the API* at that point (binary, not source) for *Flink 1.2* and add a big note in the release docs. An uncomfortable step, but the alternatives are quite bad, too. Have a look at what has been suggested in the pull request discussion and please let us know what you think about that so we can proceed. Greetings, Stephan
