错误kafka010.KafkaRDD：Kafka ConsumerRecord无法序列化。在调用.persist或.window之前，使用.map提取字段

Question

我使用的是yarn and cluster模式，streaming-kafka版本是0.10。然而， 经常出现以下错误“ ERROR kafka010.KafkaRDD：Kafka ConsumerRecord无法序列化。使用.map提取字段，然后调用.persist或.window”吗？是什么原因？

val topic = Configuration.new_feed
    val groupId = "star_feed_consumer"
    val duration = "1000"
    val kafkaParams = KafkaUtil.initKafkaParams(Configuration.bootstrap_servers_log, groupId, duration)
    val topics = Array(topic)
    val stream = KafkaUtils.createDirectStream(ssc, PreferConsistent, Subscribe[String, String](topics, kafkaParams))
    val cachedStream = stream.cache()
    val new_feeds = cachedStream.map(record => parseJson(record.value))

    //new_feeds.foreachRDD(rdd => println(rdd))
    new_feeds.print(10)