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https://issues.apache.org/jira/browse/SPARK-17463?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15566427#comment-15566427
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Harish commented on SPARK-17463:
--------------------------------
No i dont have any code like that. I use pyspark .. Please find my code snippet
df1 with 60 columns (70M records)
df2 with 3000-7000 (varies) columns (10M)
join df1 and df2 with key columns (please note df1 is more granular data and
df2 one level above. So data set will grow
df3 = df1.join(df2, [keys])
aggList = [func.mean(col).alias(col + '_m') for col in df2.columns]
Last part is i do -- df4 = df3.groupBy(keys).agg(*aggList) --I applying mean to
each column of the df3 data frame which might be 3000-10000 columns.
PS: We still have issue https://issues.apache.org/jira/browse/SPARK-16845 -- So
i have to break number of columns 500 chunks
> Serialization of accumulators in heartbeats is not thread-safe
> --------------------------------------------------------------
>
> Key: SPARK-17463
> URL: https://issues.apache.org/jira/browse/SPARK-17463
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 2.0.0
> Reporter: Josh Rosen
> Assignee: Shixiong Zhu
> Priority: Critical
> Fix For: 2.0.1, 2.1.0
>
>
> Check out the following {{ConcurrentModificationException}}:
> {code}
> 16/09/06 16:10:29 WARN NettyRpcEndpointRef: Error sending message [message =
> Heartbeat(2,[Lscala.Tuple2;@66e7b6e7,BlockManagerId(2, HOST, 57743))] in 1
> attempts
> org.apache.spark.SparkException: Exception thrown in awaitResult
> at
> org.apache.spark.rpc.RpcTimeout$$anonfun$1.applyOrElse(RpcTimeout.scala:77)
> at
> org.apache.spark.rpc.RpcTimeout$$anonfun$1.applyOrElse(RpcTimeout.scala:75)
> at
> scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:33)
> at
> org.apache.spark.rpc.RpcTimeout$$anonfun$addMessageIfTimeout$1.applyOrElse(RpcTimeout.scala:59)
> at
> org.apache.spark.rpc.RpcTimeout$$anonfun$addMessageIfTimeout$1.applyOrElse(RpcTimeout.scala:59)
> at scala.PartialFunction$OrElse.apply(PartialFunction.scala:162)
> at org.apache.spark.rpc.RpcTimeout.awaitResult(RpcTimeout.scala:83)
> at
> org.apache.spark.rpc.RpcEndpointRef.askWithRetry(RpcEndpointRef.scala:102)
> at
> org.apache.spark.executor.Executor.org$apache$spark$executor$Executor$$reportHeartBeat(Executor.scala:518)
> at
> org.apache.spark.executor.Executor$$anon$1$$anonfun$run$1.apply$mcV$sp(Executor.scala:547)
> at
> org.apache.spark.executor.Executor$$anon$1$$anonfun$run$1.apply(Executor.scala:547)
> at
> org.apache.spark.executor.Executor$$anon$1$$anonfun$run$1.apply(Executor.scala:547)
> at org.apache.spark.util.Utils$.logUncaughtExceptions(Utils.scala:1862)
> at org.apache.spark.executor.Executor$$anon$1.run(Executor.scala:547)
> at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
> at
> java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
> 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.util.ConcurrentModificationException
> at java.util.ArrayList.writeObject(ArrayList.java:766)
> at sun.reflect.GeneratedMethodAccessor20.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.lang.reflect.Method.invoke(Method.java:497)
> at
> java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1028)
> at
> java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
> at
> java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
> at
> java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
> at
> java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
> at
> java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
> at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1378)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
> at
> java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
> at
> java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
> at
> java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
> at
> java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
> at
> java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
> at
> java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
> at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1378)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
> at
> java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
> at
> java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
> at
> java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
> at
> java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
> at
> java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
> at
> java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
> at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
> at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
> at
> org.apache.spark.serializer.JavaSerializationStream.writeObject(JavaSerializer.scala:43)
> at
> org.apache.spark.serializer.JavaSerializerInstance.serialize(JavaSerializer.scala:100)
> at org.apache.spark.rpc.netty.NettyRpcEnv.serialize(NettyRpcEnv.scala:253)
> at org.apache.spark.rpc.netty.NettyRpcEnv.ask(NettyRpcEnv.scala:227)
> at
> org.apache.spark.rpc.netty.NettyRpcEndpointRef.ask(NettyRpcEnv.scala:508)
> at
> org.apache.spark.rpc.RpcEndpointRef.askWithRetry(RpcEndpointRef.scala:101)
> ... 13 more
> {code}
> Even though accumulators aren't thread-safe they can be concurrently read
> while serializing executor heartbeats and modified while tasks are running,
> leading to ConcurrentModificationException errors (thereby leading to missing
> heartbeats) or leading to inconsistent data (since individual fields of a
> multi-field object might be serialized at different points in time, leading
> to inconsistencies in accumulators like LongAccum).
> This seems like a pretty serious issue but I'm not sure what's the best way
> to fix this. An obvious fix would be to properly synchronize all accesses to
> the fields of our accumulators and to synchronize the writeObject and
> writeKryo methods, but this may have an adverse performance impact
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