to reproduce:
create tbl (...) engine=cassandra ...
use tbl;
select smth from tbl;

/restart cassandra/

try to repeat last query:
ERROR 1928 (HY000): Internal error: 'Thrift exception: write() send(): Broken pipe'
ERROR 1928 (HY000): Internal error: 'Thrift exception: Called write on non-open socket'

restart mysql service fixes problem.

socket leak?
and seems affected 10.0.2 too (at least looking in sources).