Fix accounting bug found by CI

openmsistream/kafka_wrapper/controlled_message_reproducer.py

@@ -208,7 +208,7 @@ def __consume_messages_while_alive(self, consumer):
             with self.lock:
                 self.n_msgs_processed += 1
                 self.n_msgs_processed_since_last_heartbeat += 1
-                self.n_bytes_read_since_last_heartbeat += get_message_length(msg)
+                self.n_bytes_processed_since_last_heartbeat += get_message_length(msg)
             if not consumer.message_consumed_before(msg):
                 tps = consumer.commit(msg)
                 if tps is None: