From time to time you may see these peculiar “invalid query handle” errors appear, especially if your Dashboard is taking a long time to load:
Invalid query handle exceptions are triggered when Arcengine and Impala based queries are cancelled manually or from the backend due to a session/query timeout. These timeouts happen because a user may be waiting for the Dashboard to load and decide to navigate to another tab in the browser, which then causes the backend to think that the session/query has gone stale after 60 seconds or so when the Arcadia UI stops polling/fetching results from the query handle (this timeout is configureable from the Arcadia UI and Cloudera Manager/Ambari).
These errors don’t indicate an error with the data or the Dashboard configuration, and can usually be resolved by refreshing the page. However, if these are happening consistently its a sign that your Dashboard most likely needs some performance tuning because the queries are taking too long and the users are becoming impatient and navigating away from the slow loading Dashboard.
Its also not recommended to make these timeouts much larger than 60-300 seconds as it becomes important to cancel a user’s queries if they’re no longer interested in the Dashboard and then release the memory resources back into the pool for other queries to use.