Github user andreaTP commented on the issue: https://github.com/apache/zeppelin/pull/2322 Looking at the code it looks quite harmful also the pattern used [here](https://github.com/apache/zeppelin/blob/master/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreterEventClient.java#L138), [here](https://github.com/apache/zeppelin/blob/master/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreterEventClient.java#L191) and [here](https://github.com/apache/zeppelin/blob/master/zeppelin-interpreter/src/main/java/org/apache/zeppelin/interpreter/remote/RemoteInterpreterEventClient.java#L245) if anything goes wrong the Thread can stay in `wait` status potentially forever and operations performed there are all but not transactional. Could I ask if somebody can at least provide some kind of deadline also for those? Better will be a little refactoring using something like [ConcurrentHashMap](https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentHashMap.html) for operations. I can even do the refactoring if I have positive feedbacks, anyhow I believe this PR is ok as is and I open a new issue and new PR in case.
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