Github user zjffdu commented on the issue: https://github.com/apache/zeppelin/pull/1503 That's correct for LivySparkInterpreter, LivyPySparkInterpreter and LivySparkRInterpreter. Because they use FIFOScheduler. If you check the implenentaion of FIFOScheduler, there's only one thread in it, and each job will run in FIFO order. But this is different for LivySparkSQLInterpreter as it can use ParallelScheduler if set zeppelin.livy.concurrentSQL as true. This is why I mention before there're many issues in LivyInterpreter, it doesn't make sense to use FIFOScheduler for LivySparkInterpreter, LivyPySparkInterpreter and LivySparkRInterpreter. Because each user's sessions are isolated in livy, we should use ParallelScheduler.
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