Major Description
Currently Batcher::ProcessWriteResponse will log a VLOG(1) entry for every row error it experiences. When using INSERT IGNORE in Impala, this can yield thousands of logs per second and makes it extremely slow.
We should consider bumping this to a higher vlog level, or pushing the 'insert ignore' flag into the operations themselves (even before KUDU-1563 is finished we could just drop the errors inside the client side)