private KafkaProducer<String, byte[]> selectProducer() {
        if (CollectionUtils.isEmpty(kafkaSenders)) {
            LOGGER.error("send job[{}] data err, empty kafka sender", jobInstanceId);
            return null;
        }
        KafkaSender sender = kafkaSenders.get(
                (KAFKA_SENDER_INDEX.getAndIncrement() & Integer.MAX_VALUE) % kafkaSenders.size());
        return sender.getProducer();
    }
take batchMsg from sendQueue and send to kafka
inlong-agent/agent-plugins/src/main/java/org/apache/inlong/agent/plugin/sinks/KafkaSink.java