Sorry for the delay.   Here is an example of HAProxy configuration: https://docs.cloudera.com/documentation/enterprise/6/6.3/topics/impala_proxy.html#tut_proxy. Please check if you set balance to SOURCE for ODBC proxy. I used to see some client (I can't remember if it's an ODBC or JDBC client) opened a connection and reused an existing session. If the balance is not set to SOURCE, HAProxy could forward the connection to another impala daemon so the client would hit 'Invalid query handle'.   You can enable debug level logging for Impala ODBC Driver. After the issue occurs, you can trace the operations in ODBC driver logs. If the client opened a connection prior to "Invalid query handle", the LB could forward the connection to a wrong impala daemon. Then you can look up impalad logs by the timestamp to figure out which impala daemon the client connected to and check if the impala daemon is the coordinator of the query (it can be found from query profile). Otherwise, you need to trace the query id in the impalad coordinator logs to find out why it returned "Invalid query handle" to the client. ... View more