Spark（Java）的一些坑

0.2542019.01.06 20:47:16字数 267阅读 1284

1. org.apache.spark.SparkException: Task not serializable

广播变量时使用一些自定义类会出现无法序列化，实现 java.io.Serializable 即可。

public class CollectionBean implements Serializable {

2. SparkSession如何广播变量

想要使用SparkSession广播变量，查了很久，有的人是通过得到SparkContext，再用SparkContext广播，但SparkContext第二个参数会要求一个scala的classtag：

ClassTag tag = scala.reflect.ClassTag$.MODULE$.apply(String.class);
Broadcast s=spark.sparkContext().broadcast(args[0], tag);

但是我广播的变量是有自定义类型的Map，这个ClassTag不能创建带泛型的类型，于是问题绕回了怎么用 SparkSession 获取 JavaSparkContext：

Broadcast<Map<String, CollectionBean>> broadcastPlayList = JavaSparkContext.fromSparkContext(session.sparkContext()).broadcast(col);

3. 在广播变量时出现 UnsupportedOperationException

java.lang.UnsupportedOperationException 
at org.apache.spark.util.Utils$.tryOrIOException(Utils.scala:1276)
at org.apache.spark.broadcast.TorrentBroadcast.readBroadcastBlock(TorrentBroadcast.scala:206) 
at org.apache.spark.broadcast.TorrentBroadcast._value$lzycompute(TorrentBroadcast.scala:66) 
at org.apache.spark.broadcast.TorrentBroadcast._value(TorrentBroadcast.scala:66) 
at org.apache.spark.broadcast.TorrentBroadcast.getValue(TorrentBroadcast.scala:96)
at UAARead.SparkHiveETL$2.call(SparkHiveETL.java:109) 
at UAARead.SparkHiveETL$2.call(SparkHiveETL.java:99)
at org.apache.spark.api.java.JavaPairRDD$$anonfun$toScalaFunction$1.apply(JavaPairRDD.scala:1040) at scala.collection.Iterator$$anon$11.next(Iterator.scala:328)
at scala.collection.Iterator$$anon$14.hasNext(Iterator.scala:389) 
at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:327)
at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:327) 
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIterator.processNext(Unknown Source) at org.apache.spark.sql.execution.BufferedRowIterator.hasNext(BufferedRowIterator.java:43) 
at org.apache.spark.sql.execution.WholeStageCodegenExec$$anonfun$8$$anon$1.hasNext(WholeStageCodegenExec.scala:377) at scala.collection.Iterator$class.foreach(Iterator.scala:727) 
at org.apache.spark.sql.execution.WholeStageCodegenExec$$anonfun$8$$anon$1.foreach(WholeStageCodegenExec.scala:375) 
at org.apache.spark.sql.hive.SparkHiveWriterContainer.writeToFile(hiveWriterContainers.scala:184) at org.apache.spark.sql.hive.execution.InsertIntoHiveTable$$anonfun$saveAsHiveFile$3.apply(InsertIntoHiveTable.scala:210) at org.apache.spark.sql.hive.execution.InsertIntoHiveTable$$anonfun$saveAsHiveFile$3.apply(InsertIntoHiveTable.scala:210) at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87) 
at org.apache.spark.scheduler.Task.run(Task.scala:99) 
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:322) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745) Caused by: java.lang.UnsupportedOperationException 
at java.util.AbstractMap.put(AbstractMap.java:209) 
at com.esotericsoftware.kryo.serializers.MapSerializer.read(MapSerializer.java:162)
 at com.esotericsoftware.kryo.serializers.MapSerializer.read(MapSerializer.java:39)
 at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:790) 
at org.apache.spark.serializer.KryoDeserializationStream.readObject(KryoSerializer.scala:244)
 at org.apache.spark.broadcast.TorrentBroadcast$$anonfun$9.apply(TorrentBroadcast.scala:290) 
at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1303) 
at org.apache.spark.broadcast.TorrentBroadcast$.unBlockifyObject(TorrentBroadcast.scala:291) 
at org.apache.spark.broadcast.TorrentBroadcast$$anonfun$readBroadcastBlock$1.apply(TorrentBroadcast.scala:225) at org.apache.spark.util.Utils$.tryOrIOException(Utils.scala:1269) ... 25 more Driver stacktrace:

解决方法：new 一个 map，把rdd转换的map putall进去广播

Map col =new HashMap();
col.putAll(collection_bean_rdd.collectAsMap());

集合AbstractMap 问题 UnsupportedOperationException

https://*.com/questions/43023961/spark-kryo-serializers-and-broadcastmapobject-iterablegowalladatalocation

4. 最最最坑的一个

查看日志发现DAG只出现了一半，后面的语句不运行了，找了几天的bug，竟然是session.sql("")的时候，黏贴sql语句分号黏贴上了，这里不能加分号，一个语句一个session.sql("")！