@Override
    public void close() throws IOException {
        try {
            if (session != null) {
                session.close();
            }
        } catch (Exception e) {
            LOG.error("Error while closing session.", e);
        }
        try {
            if (cluster != null) {
                cluster.close();
            }
        } catch (Exception e) {
            LOG.error("Error while closing cluster.", e);
        }
        LOG.info("close cassandra is successed!");
    }
Executes prepared statement and closes all resources of this instance.

@throws IOException Thrown, if the input could not be closed properly.
cassandra/cassandra-sink/src/main/java/com/dtstack/flink/sql/sink/cassandra/CassandraOutputFormat.java