Github user tillrohrmann commented on the issue:
https://github.com/apache/flink/pull/4751
I assume that the `Thread.sleep(1)` should not do much harm if the Kafka
Producer already blocks due to buffering and I/O. If it should not block, then
the `Thread.sleep(1)` will give other threads the chance to execute when having
only scarce resources (e.g. on Travis).
I agree with @pnowojski that this is not a stress test and we have seen in
the past that tests became unstable due to resource scarcity. Therefore I would
like to merge this PR if Travis gives green light and @StephanEwen does not
object.
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