@Override
            public List<ClientResponse> poll(long timeoutMs, long now) {
                canSendMore = inFlightRequestCount() < 1;
                return super.poll(timeoutMs, now);
            }
It creates response with new leader info and new nodes, as stated in KIP-951
clients/src/test/java/org/apache/kafka/clients/producer/internals/SenderTest.java