So IDLE_SESSION_TIMEOUT doesn't actually do anything if you set it in impala-shell. There's a technical distinction here - "set" in impala-shell is implemented in the shell itself, then send along with the queries. Whereas if you run "set" as a statement through, say, the JDBC driver, then "set" is run as a server-side command that modifies the session state.   I tried to reproduce the issue on my local Impala environment, but couldn't. I was watching the /sessions page in the debug page and I could see the "last accessed" time get continually incremented while the query was in the queue. I think any timeout issue probably got indirectly fixed by https://issues.apache.org/jira/browse/IMPALA-5216 in CDH6.1/Impala 3.1, since the query state would be polled directly by impala-shell while the query is in the queue, rather than having impala-shell blocked waiting for a response.   Thanks for submitting the support request, that should help get to the bottom of this. ... View more