--use_krpc was introduced in 2.9.0 during development of adopting KRPC for DataStream services (
IMPALA-2567). It was initially hidden and set to false as it wasn't fully implemented yet. Since 2.12.0 and 3.0, this flag is set to true by default. Going forward, we will port more services to KRPC and it's become very burdensome to keep both Thrift RPC and KRPC implementation for converted RPCs. The best route forward is to drop this flag for 3.0+ releases.