Pyspark-随着数据帧变大而中断

Question

我有一个脚本，直到这一行都很好：

df_3 = df_2.groupBy("id").pivot("key").agg(collect_list("value")).select('col1','col2')

问题是由pivot引起的java.lang.NullPointerException。我相信df_2大约有600K行，只有几列，如果我之前加上这一行，它就行了：

df_2 = df_2.limit(27000)

但是任何更高的值都会导致空指针异常。为什么会发生这种情况？我以为600K行不会是那么大的数据帧，但一旦我超过~27K，它似乎就坏了。

以下是导致它的代码：

parse_xml_udf = udf(parse_xml, ArrayType(MapType(StringType(),StringType())))
parsed_df = xml_df.withColumn('parsed_xml', parse_xml_udf(xml_df['xml_strs']))
df_1 = parsed_df.withColumn('exploded_arr',explode('parsed_xml')) 
df_2 = df_1.select(explode('exploded_arr'),*df_1.columns)

完整堆叠：

20/07/07 10:46:08 WARN scheduler.TaskSetManager: Lost task 0.0 in stage 1.0 (TID 2, _, executor 2): java.lang.NullPointerException
at org.apache.spark.sql.catalyst.expressions.codegen.UnsafeRowWriter.write(UnsafeRowWriter.java:210)
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$SpecificUnsafeProjection.apply(Unknown Source)
at org.apache.spark.sql.execution.GenerateExec$$anonfun$doExecute$1$$anonfun$apply$9.apply(GenerateExec.scala:111)
at org.apache.spark.sql.execution.GenerateExec$$anonfun$doExecute$1$$anonfun$apply$9.apply(GenerateExec.scala:109)
at scala.collection.Iterator$$anon$11.next(Iterator.scala:409)
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIterator.agg_doAggregateWithKeys$(Unknown Source)
at org.apache.spark.sql.catalyst.expressions.GeneratedClass$GeneratedIterator.processNext(Unknown Source)
at org.apache.spark.sql.execution.BufferedRowIterator.hasNext(BufferedRowIterator.java:43)
at org.apache.spark.sql.execution.WholeStageCodegenExec$$anonfun$8$$anon$1.hasNext(WholeStageCodegenExec.scala:377)
at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:408)
at org.apache.spark.shuffle.sort.BypassMergeSortShuffleWriter.write(BypassMergeSortShuffleWriter.java:126)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:96)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:53)
at org.apache.spark.scheduler.Task.run(Task.scala:99)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:322)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
20/07/07 10:46:08 INFO scheduler.TaskSetManager: Starting task 0.1 in stage 1.0 (TID 4, _, executor 2, partition 0, PROCESS_LOCAL, 19119331 bytes)
20/07/07 10:46:11 INFO scheduler.TaskSetManager: Lost task 1.0 in stage 1.0 (TID 3) on _, executor 1: java.lang.NullPointerException (null) [duplicate 1]
20/07/07 10:46:11 INFO scheduler.TaskSetManager: Starting task 1.1 in stage 1.0 (TID 5, _,executor 1, partition 1, PROCESS_LOCAL, 19064182 bytes)
20/07/07 10:46:12 INFO scheduler.TaskSetManager: Lost task 0.1 in stage 1.0 (TID 4) on _, executor 2: java.lang.NullPointerException (null) [duplicate 2]
20/07/07 10:46:12 INFO scheduler.TaskSetManager: Starting task 0.2 in stage 1.0 (TID 6, _, executor 2, partition 0, PROCESS_LOCAL, 19119331 bytes)
20/07/07 10:46:15 INFO scheduler.TaskSetManager: Lost task 1.1 in stage 1.0 (TID 5) on _, executor 1: java.lang.NullPointerException (null) [duplicate 3]
20/07/07 10:46:15 INFO scheduler.TaskSetManager: Starting task 1.2 in stage 1.0 (TID 7, _, executor 1, partition 1, PROCESS_LOCAL, 19064182 bytes)
20/07/07 10:46:15 INFO scheduler.TaskSetManager: Lost task 0.2 in stage 1.0 (TID 6) on _, executor 2: java.lang.NullPointerException (null) [duplicate 4]
20/07/07 10:46:15 INFO scheduler.TaskSetManager: Starting task 0.3 in stage 1.0 (TID 8, _, executor 2, partition 0, PROCESS_LOCAL, 19119331 bytes)
20/07/07 10:46:17 INFO scheduler.TaskSetManager: Lost task 1.2 in stage 1.0 (TID 7) on _, executor 1: java.lang.NullPointerException (null) [duplicate 5]
20/07/07 10:46:18 INFO scheduler.TaskSetManager: Starting task 1.3 in stage 1.0 (TID 9, _, executor 1, partition 1, PROCESS_LOCAL, 19064182 bytes)
20/07/07 10:46:18 INFO scheduler.TaskSetManager: Lost task 0.3 in stage 1.0 (TID 8) on _, executor 2: java.lang.NullPointerException (null) [duplicate 6]
20/07/07 10:46:18 ERROR scheduler.TaskSetManager: Task 0 in stage 1.0 failed 4 times; aborting job
20/07/07 10:46:18 INFO cluster.YarnScheduler: Cancelling stage 1
20/07/07 10:46:18 INFO cluster.YarnScheduler: Stage 1 was cancelled
20/07/07 10:46:18 INFO scheduler.DAGScheduler: ShuffleMapStage 1 (pivot at NativeMethodAccessorImpl.java:0) failed in 16.373 s due to Job aborted due to stage failure: Task 0 in stage 1.0 failed 4 times, most recent failure: Lost task 0.3 in stage 1.0 (TID 8, _, executor 2): java.lang.NullPointerException
Driver stacktrace:
20/07/07 10:46:18 INFO scheduler.DAGScheduler: Job 1 failed: pivot at NativeMethodAccessorImpl.java:0, took 16.448475 s
20/07/07 10:46:18 WARN spark.ExecutorAllocationManager: No stages are running, but numRunningTasks != 0
Traceback (most recent call last):
File "_", line 74, in <module>
df_3 = df_2.groupBy("id").pivot("key").agg(collect_list("value")).select('col1','col2')
File "_/lib/spark2/python/lib/pyspark.zip/pyspark/sql/group.py", line 192, in pivot
File "_/lib/spark2/python/lib/py4j-0.10.4-src.zip/py4j/java_gateway.py", line 1133, in __call__
File "_/lib/spark2/python/lib/pyspark.zip/pyspark/sql/utils.py", line 63, in deco
File "_/lib/spark2/python/lib/py4j-0.10.4-src.zip/py4j/protocol.py", line 319, in get_return_value
py4j.protocol.Py4JJavaError: An error occurred while calling o94.pivot.
: org.apache.spark.SparkException: Job aborted due to stage failure: Task 0 in stage 1.0 failed 4 times, most recent failure: Lost task 0.3 in stage 1.0 (TID 8, _, executor 2): java.lang.NullPointerException
Driver stacktrace:
at org.apache.spark.scheduler.DAGScheduler.org$apache$spark$scheduler$DAGScheduler$$failJobAndIndependentStages(DAGScheduler.scala:1435)
at org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1423)
at org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1422)
at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
at org.apache.spark.scheduler.DAGScheduler.abortStage(DAGScheduler.scala:1422)
at org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:802)
at org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:802)
at scala.Option.foreach(Option.scala:257)
at org.apache.spark.scheduler.DAGScheduler.handleTaskSetFailed(DAGScheduler.scala:802)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.doOnReceive(DAGScheduler.scala:1650)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1605)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1594)
at org.apache.spark.util.EventLoop$$anon$1.run(EventLoop.scala:48)
at org.apache.spark.scheduler.DAGScheduler.runJob(DAGScheduler.scala:628)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:1918)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:1931)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:1944)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:1958)
at org.apache.spark.rdd.RDD$$anonfun$collect$1.apply(RDD.scala:935)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:362)
at org.apache.spark.rdd.RDD.collect(RDD.scala:934)
at org.apache.spark.RangePartitioner$.sketch(Partitioner.scala:266)
at org.apache.spark.RangePartitioner.<init>(Partitioner.scala:128)
at org.apache.spark.sql.execution.exchange.ShuffleExchange$.prepareShuffleDependency(ShuffleExchange.scala:218)
at org.apache.spark.sql.execution.exchange.ShuffleExchange.prepareShuffleDependency(ShuffleExchange.scala:84)
at org.apache.spark.sql.execution.exchange.ShuffleExchange$$anonfun$doExecute$1.apply(ShuffleExchange.scala:121)
at org.apache.spark.sql.execution.exchange.ShuffleExchange$$anonfun$doExecute$1.apply(ShuffleExchange.scala:112)
at org.apache.spark.sql.catalyst.errors.package$.attachTree(package.scala:52)
at org.apache.spark.sql.execution.exchange.ShuffleExchange.doExecute(ShuffleExchange.scala:112)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:114)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:114)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:135)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:132)
at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:113)
at org.apache.spark.sql.execution.InputAdapter.inputRDDs(WholeStageCodegenExec.scala:235)
at org.apache.spark.sql.execution.SortExec.inputRDDs(SortExec.scala:121)
at org.apache.spark.sql.execution.WholeStageCodegenExec.doExecute(WholeStageCodegenExec.scala:368)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:114)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:114)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:135)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:132)
at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:113)
at org.apache.spark.sql.execution.DeserializeToObjectExec.doExecute(objects.scala:90)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:114)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:114)
at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:135)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:132)
at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:113)
at org.apache.spark.sql.execution.QueryExecution.toRdd$lzycompute(QueryExecution.scala:87)
at org.apache.spark.sql.execution.QueryExecution.toRdd(QueryExecution.scala:87)
at org.apache.spark.sql.Dataset.rdd$lzycompute(Dataset.scala:2547)
at org.apache.spark.sql.Dataset.rdd(Dataset.scala:2544)
at org.apache.spark.sql.RelationalGroupedDataset.pivot(RelationalGroupedDataset.scala:321)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244)
at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
at py4j.Gateway.invoke(Gateway.java:280)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:214)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException

Answer 1

如果看到工作程序在尝试访问仅存在于驱动程序而不存在于工作程序上的SparkContext对象时抛出NullPointerException。

在第二种情况下，我的直觉是，这项工作是由司机在当地完成的，纯粹是意外。更多阅读：这里和这里