We started not so long ago to use a Hadoop stack (hdfs / hive / spark) with DSS. From the first set of logs you are showing this seems like a problem in the hive server.
We got the same kind of problems at the beginning, and they were found to be related to problems with the memory management of the Hive server. We could notice that the problems were not from the DSS side because the whole hive server was down usually (until it re-scaled itself to restart).
So that would be the first thing to check. If the hive server is still up, then there could be a problem with the network connection (either a configuration problem or a hardware problem). The kind of messages that you are getting later also seem to point in the same direction (specially when you see the error to connect to DSS).
If you don't find the problem there, then the next step would be to create a support ticket with Dataiku, as it doesn't seem as an easy to reproduce problem.
Hope this helps, and good luck