我正在尝试将流数据保存到 Kafka 的cassandra中 . 我能够读取和解析数据但是当我在下面的行中调用以保存数据时,我得到的是 Task not Serializable
异常 . 我的课程正在扩展可序列化,但不确定为什么我看到这个错误,谷歌搜索3小时后没有得到太多的帮助,有些机构可以提供任何指示吗?
val collection = sc.parallelize(Seq((obj.id, obj.data)))
collection.saveToCassandra("testKS", "testTable ", SomeColumns("id", "data"))`
import org.apache.spark.SparkConf
import org.apache.spark.SparkContext
import org.apache.spark.sql.SaveMode
import org.apache.spark.streaming.Seconds
import org.apache.spark.streaming.StreamingContext
import org.apache.spark.streaming.kafka.KafkaUtils
import com.datastax.spark.connector._
import kafka.serializer.StringDecoder
import org.apache.spark.rdd.RDD
import com.datastax.spark.connector.SomeColumns
import java.util.Formatter.DateTime
object StreamProcessor extends Serializable {
def main(args: Array[String]): Unit = {
val sparkConf = new SparkConf().setMaster("local[2]").setAppName("StreamProcessor")
.set("spark.cassandra.connection.host", "127.0.0.1")
val sc = new SparkContext(sparkConf)
val ssc = new StreamingContext(sc, Seconds(2))
val sqlContext = new SQLContext(sc)
val kafkaParams = Map("metadata.broker.list" -> "localhost:9092")
val topics = args.toSet
val stream = KafkaUtils.createDirectStream[String, String, StringDecoder, StringDecoder](
ssc, kafkaParams, topics)
stream.foreachRDD { rdd =>
if (!rdd.isEmpty()) {
try {
rdd.foreachPartition { iter =>
iter.foreach {
case (key, msg) =>
val obj = msgParseMaster(msg)
val collection = sc.parallelize(Seq((obj.id, obj.data)))
collection.saveToCassandra("testKS", "testTable ", SomeColumns("id", "data"))
}
}
}
}
}
ssc.start()
ssc.awaitTermination()
}
import org.json4s._
import org.json4s.native.JsonMethods._
case class wordCount(id: Long, data: String) extends serializable
implicit val formats = DefaultFormats
def msgParseMaster(msg: String): wordCount = {
val m = parse(msg).extract[wordCount]
return m
}
}
我正进入(状态
org.apache.spark.SparkException:任务不可序列化
下面是完整的日志
16/08/06 10:24:52错误JobScheduler:运行作业流作业时出错1470504292000 ms.0 org.apache.spark.SparkException:任务不可序列化在org.apache.spark.util.ClosureCleaner $ .ensureSerializable(ClosureCleaner . scala:304)在org.apache.spark.util.ClosureCleaner $ .org $ apache $ spark $ util $ ClosureCleaner $$ clean(ClosureCleaner.scala:294)at org.apache.spark.util.ClosureCleaner $ .clean(ClosureCleaner) .scala:122)org.apache.spark.SparkContext.clean(SparkContext.scala:2055)org.apache.spark.rdd.RDD $$ anonfun $ foreachPartition $ 1.apply(RDD.scala:919)at org . 位于org.apache.spark.rdd的org.apache.spark.rdd.RDDOperationScope $ .withScope(RDDOperationScope.scala:150)的apache.spark.rdd.RDD $$ anonfun $ foreachPartition $ 1.apply(RDD.scala:918) .RDDOperationScope $ .withScope(RDDOperationScope.scala:111)atg.apache.spark.rdd.RDD.withScope(RDD.scala:316)at org.apache.spark.rdd.RDD.foreachPartition(RDD.scala:918)在
2 回答
SparkContext
isn 't serializable, you can' t在foreachRDD
中使用它,并且从图形的使用中你不需要它 . 相反,您可以简单地映射每个RDD,解析相关数据并将新RDD保存到cassandra:您不能在传递给
foreachPartition
的函数中调用sc.parallelize
- 该函数必须被序列化并发送给每个执行程序,并且SparkContext
(故意)不可序列化(它应该只驻留在驱动程序应用程序中,而不是执行程序中) .