I’ve created a CLI driver for a Spark version of a Mahout job called "item
similarity" with several tests that all work fine on local[4] Spark standalone.
The code even reads and writes to clustered HDFS. But switching to clustered
Spark has a problem that seems tied to a broadcast and/or serialization.
The code uses HashBiMap, which is a Guava Java thing. There are two of these
created for every Mahout drm (a distributed matrix), for bi-directional row and
column ID lookup. They are created once and then broadcast for access
everywhere.
When I run this on clustered Spark I get the following error. At one point we
were using HashMaps and they seemed to work on the cluster. So I suspect
something about the HashBiMap is causing the problem. I’m also suspicious that
it may have to do with serialization in the broadcast. Here is a snippet of
code and the error.
Any ideas?
// create BiMaps for bi-directional lookup of ID by either Mahout ID or
external ID
// broadcast them for access in distributed processes, so they are not
recalculated in every task.
// rowIDDictionary is a HashBiMap[String, Int]
val rowIDDictionary = asOrderedDictionary(rowIDs) // this creates the
HashBiMap in a non-dsitributed manner
val rowIDDictionary_bcast = mc.broadcast(rowIDDictionary)
val columnIDDictionary = asOrderedDictionary(columnIDs)) // this creates
the HashBiMap in a non-dsitributed manner
val columnIDDictionary_bcast = mc.broadcast(columnIDDictionary)
val indexedInteractions =
interactions.map { case (rowID, columnID) => //<<<<<<<<<<< this is
the stage being submitted before the error
val rowIndex = rowIDDictionary_bcast.value.get(rowID).get
val columnIndex = columnIDDictionary_bcast.value.get(columnID).get
rowIndex -> columnIndex
}
The error seems to happen in executing interactions.map when accessing the
_bcast vals. Any idea where to start looking for this?
14/06/26 11:23:36 INFO scheduler.DAGScheduler: Submitting Stage 9
(MappedRDD[17] at map at TextDelimitedReaderWriter.scala:83), which has no
missing parents
14/06/26 11:23:36 INFO scheduler.DAGScheduler: Submitting 2 missing tasks from
Stage 9 (MappedRDD[17] at map at TextDelimitedReaderWriter.scala:83)
14/06/26 11:23:36 INFO scheduler.TaskSchedulerImpl: Adding task set 9.0 with 2
tasks
14/06/26 11:23:36 INFO scheduler.TaskSetManager: Starting task 9.0:0 as TID 16
on executor 0: occam4 (PROCESS_LOCAL)
14/06/26 11:23:36 INFO scheduler.TaskSetManager: Serialized task 9.0:0 as 2418
bytes in 0 ms
14/06/26 11:23:36 INFO scheduler.TaskSetManager: Starting task 9.0:1 as TID 17
on executor 0: occam4 (PROCESS_LOCAL)
14/06/26 11:23:36 INFO scheduler.TaskSetManager: Serialized task 9.0:1 as 2440
bytes in 0 ms
14/06/26 11:23:36 WARN scheduler.TaskSetManager: Lost TID 16 (task 9.0:0)
14/06/26 11:23:36 WARN scheduler.TaskSetManager: Loss was due to
java.lang.NullPointerException
java.lang.NullPointerException
at com.google.common.collect.HashBiMap.seekByKey(HashBiMap.java:180)
at com.google.common.collect.HashBiMap.put(HashBiMap.java:230)
at com.google.common.collect.HashBiMap.put(HashBiMap.java:218)
at
com.esotericsoftware.kryo.serializers.MapSerializer.read(MapSerializer.java:135)
at
com.esotericsoftware.kryo.serializers.MapSerializer.read(MapSerializer.java:17)
at com.esotericsoftware.kryo.Kryo.readClassAndObject(Kryo.java:729)
at
org.apache.spark.serializer.KryoDeserializationStream.readObject(KryoSerializer.scala:102)
at
org.apache.spark.broadcast.HttpBroadcast$.read(HttpBroadcast.scala:165)
at
org.apache.spark.broadcast.HttpBroadcast.readObject(HttpBroadcast.scala:56)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at
java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:969)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at
java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1775)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1327)
at
java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1969)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1893)
at
java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1775)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1327)
at
java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1969)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1893)
at
java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1775)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1327)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:349)
at
org.apache.spark.serializer.JavaDeserializationStream.readObject(JavaSerializer.scala:40)
at
org.apache.spark.scheduler.ShuffleMapTask$.deserializeInfo(ShuffleMapTask.scala:69)
at
org.apache.spark.scheduler.ShuffleMapTask.readExternal(ShuffleMapTask.scala:138)
at
java.io.ObjectInputStream.readExternalData(ObjectInputStream.java:1814)
at
java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1773)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1327)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:349)
at
org.apache.spark.serializer.JavaDeserializationStream.readObject(JavaSerializer.scala:40)
at
org.apache.spark.serializer.JavaSerializerInstance.deserialize(JavaSerializer.scala:62)
at
org.apache.spark.executor.Executor$TaskRunner$$anonfun$run$1.apply$mcV$sp(Executor.scala:193)
at
org.apache.spark.deploy.SparkHadoopUtil$$anon$1.run(SparkHadoopUtil.scala:42)
at
org.apache.spark.deploy.SparkHadoopUtil$$anon$1.run(SparkHadoopUtil.scala:41)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
at
org.apache.spark.deploy.SparkHadoopUtil.runAsUser(SparkHadoopUtil.scala:41)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:176)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:662)
