一、spark错误

1、

17/07/17 15:34:55 ERROR yarn.ApplicationMaster: User class threw exception: java.lang.UnsupportedOperationException: empty collection
java.lang.UnsupportedOperationException: empty collection
	at org.apache.spark.rdd.RDD$$anonfun$reduce$1$$anonfun$apply$40.apply(RDD.scala:1027)
	at org.apache.spark.rdd.RDD$$anonfun$reduce$1$$anonfun$apply$40.apply(RDD.scala:1027)
	at scala.Option.getOrElse(Option.scala:120)
	at org.apache.spark.rdd.RDD$$anonfun$reduce$1.apply(RDD.scala:1027)
	at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:150)
	at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:111)
	at org.apache.spark.rdd.RDD.withScope(RDD.scala:316)
	at org.apache.spark.rdd.RDD.reduce(RDD.scala:1007)
	at sparkoffline.DayCount$.dayCount(DayCount.scala:44)
	at sparkoffline.Main$.main(Main.scala:35)
	at sparkoffline.Main.main(Main.scala)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.spark.deploy.yarn.ApplicationMaster$$anon$2.run(ApplicationMaster.scala:558)
17/07/17 15:34:55 INFO yarn.ApplicationMaster: Final app status: FAILED, exitCode: 15, (reason: User class threw exception: java.lang.UnsupportedOperationException: empty collection)
17/07/17 15:34:55 INFO spark.SparkContext: Invoking stop() from shutdown hook

　　spark 从hbase过滤出数据形成RDD，然后再做计算，这个错误大概意思是  从hbase过滤出来的数据为空，也就是一个空的RDD

2、

org.apache.spark.shuffle.MetadataFetchFailedException: Missing an output location for shuffle 12
	at org.apache.spark.MapOutputTracker$$anonfun$org$apache$spark$MapOutputTracker$$convertMapStatuses$2.apply(MapOutputTracker.scala:548)
	at org.apache.spark.MapOutputTracker$$anonfun$org$apache$spark$MapOutputTracker$$convertMapStatuses$2.apply(MapOutputTracker.scala:544)
	at scala.collection.TraversableLike$WithFilter$$anonfun$foreach$1.apply(TraversableLike.scala:772)
	at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
	at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:108)
	at scala.collection.TraversableLike$WithFilter.foreach(TraversableLike.scala:771)
	at org.apache.spark.MapOutputTracker$.org$apache$spark$MapOutputTracker$$convertMapStatuses(MapOutputTracker.scala:544)
	at org.apache.spark.MapOutputTracker.getMapSizesByExecutorId(MapOutputTracker.scala:155)
	at org.apache.spark.shuffle.BlockStoreShuffleReader.read(BlockStoreShuffleReader.scala:47)
	at org.apache.spark.rdd.ShuffledRDD.compute(ShuffledRDD.scala:98)
	at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:306)
	at org.apache.spark.rdd.RDD.iterator(RDD.scala:270)
	at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
	at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:306)
	at org.apache.spark.rdd.RDD.iterator(RDD.scala:270)
	at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:73)
	at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
	at org.apache.spark.scheduler.Task.run(Task.scala:89)
	at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:227)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)　

org.apache.spark.shuffle.MetadataFetchFailedException: Missing an output location for shuffle
解决方案：这种问题一般发生在有大量shuffle操作的时候,task不断的failed,然后又重执行，一直循环下去，直到application失败。一般遇到这种问题提高executor内存即可,同时增加每个executor的cpu,这样不会减少task并行度。

或者改代码，替代shuffle 算子（例如reducebykey 替代groupbykey）