Github user aljoscha commented on a diff in the pull request: https://github.com/apache/flink/pull/3616#discussion_r108977967 --- Diff: flink-streaming-java/src/main/java/org/apache/flink/streaming/api/transformations/StreamTransformation.java --- @@ -221,10 +232,19 @@ public int getMaxParallelism() { * @param maxParallelism Maximum parallelism for this stream transformation. */ public void setMaxParallelism(int maxParallelism) { - Preconditions.checkArgument(maxParallelism > 0 - && maxParallelism <= StreamGraphGenerator.UPPER_BOUND_MAX_PARALLELISM, - "Maximum parallelism must be between 1 and " + StreamGraphGenerator.UPPER_BOUND_MAX_PARALLELISM - + ". Found: " + maxParallelism); + checkArgument( + parallelism != ExecutionConfig.PARALLELISM_DEFAULT, + "A maximum parallelism can only be specified with an explicitly specified " + + "parallelism."); --- End diff -- Yes, it is but the problem is that the treatment of the "default parallelism" is a bit strange. (The default parallelism is the parallelism that is set from the flink config or by the user on the command line using the `-p` parameter. Maybe we have to rework that before we can fix this. I'm starting to think that we should maybe revert the parallelism/max-parallelism changes on the release-1.2 branch and rework the whole thing properly.
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