Thrift buffer size not honored when retrieving data from Impala

When using the Thrift interface to Impala in order to retrieve data the request size influences the size of the responses, but does not control it.

In our use case we retrieve a significant number of rows and want to minimise the number of network round trips.

Details of my previous testing were posted here http://community.cloudera.com/t5/Interactive-Short-cycle-SQL/Thrift-Buffer-Size-Received-from-Impala/m-p/30863

I have repeated the tests on CDH 5.5.2 (Impala 2.3.0) and observe the same behaviour.

It appears that Impala returns data to the client when some other condition (other than buffer size or end of data) is reached. Testing with a 1M buffer resulted in 87.5% of all request still returning 512 bytes.