How to perform Secondary Sort in Spark? - scala

Question

I was searching for secondary sort using Spark and found this solution:
case class RFMCKey(cId: String, R: Double, F: Double, M: Double, C: Double)
class RFMCPartitioner(partitions: Int) extends Partitioner {
require(partitions >= 0, "Number of partitions ($partitions) cannot be negative.")
override def numPartitions: Int = partitions
override def getPartition(key: Any): Int = {
val k = key.asInstanceOf[RFMCKey]
k.cId.hashCode() % numPartitions
}
}
object RFMCKey {
implicit def orderingBycId[A <: RFMCKey] : Ordering[A] = {
Ordering.by(k => (k.R, k.F * -1, k.M * -1, k.C * -1))
}
}
Now this is the code that I am using for my RFMC (Recency, Frequency, Monetary, Clumpiness) program.
In the same code, at the end, I am doing:
val rfmcTableSorted = rfmcTable.repartitionAndSortWithinPartitions(new RFMCPartitioner(1))
But when I load this file in spark-shell, I get the following error:
<console>:130: error: RFMCKey is already defined as (compiler-generated) case class companion object RFMCKey
object RFMCKey {
^
<console>:198: error: RFMCKey.type does not take parameters
case (custId, (((rVal, fVal), mVal),cVal)) => (RFMCKey(custId, rVal, fVal, mVal, cVal), rVal+","+fVal+","+mVal+","+cVal)
^
<console>:200: error: value repartitionAndSortWithinPartitions is not a member of org.apache.spark.rdd.RDD[Nothing]
val rfmcTableSorted = rfmcTable.repartitionAndSortWithinPartitions(new RFMCPartitioner(1)).cache()
How do I circumvent this issue?
Update 1
I tried changing the order of declaration of my case class and object class and surprisingly the shell loaded the file without throwing any errors. But when I ran my program it threw a new error:
org.apache.spark.SparkException: Task not serializable
at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:166)
at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:158)
at org.apache.spark.SparkContext.clean(SparkContext.scala:1623)
at org.apache.spark.rdd.RDD.map(RDD.scala:286)
at $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$rfmc$.constructRFMC(<console>:113)
at $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:36)
at $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:41)
at $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:43)
at $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:45)
at $iwC$$iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:47)
at $iwC$$iwC$$iwC$$iwC$$iwC.<init>(<console>:49)
at $iwC$$iwC$$iwC$$iwC.<init>(<console>:51)
at $iwC$$iwC$$iwC.<init>(<console>:53)
at $iwC$$iwC.<init>(<console>:55)
at $iwC.<init>(<console>:57)
at <init>(<console>:59)
at .<init>(<console>:63)
at .<clinit>(<console>)
at .<init>(<console>:7)
at .<clinit>(<console>)
at $print(<console>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.spark.repl.SparkIMain$ReadEvalPrint.call(SparkIMain.scala:1065)
at org.apache.spark.repl.SparkIMain$Request.loadAndRun(SparkIMain.scala:1338)
at org.apache.spark.repl.SparkIMain.loadAndRunReq$1(SparkIMain.scala:840)
at org.apache.spark.repl.SparkIMain.interpret(SparkIMain.scala:871)
at org.apache.spark.repl.SparkIMain.interpret(SparkIMain.scala:819)
at org.apache.spark.repl.SparkILoop.reallyInterpret$1(SparkILoop.scala:856)
at org.apache.spark.repl.SparkILoop.interpretStartingWith(SparkILoop.scala:901)
at org.apache.spark.repl.SparkILoop.command(SparkILoop.scala:813)
at org.apache.spark.repl.SparkILoop.processLine$1(SparkILoop.scala:656)
at org.apache.spark.repl.SparkILoop.innerLoop$1(SparkILoop.scala:664)
at org.apache.spark.repl.SparkILoop.org$apache$spark$repl$SparkILoop$$loop(SparkILoop.scala:669)
at org.apache.spark.repl.SparkILoop$$anonfun$org$apache$spark$repl$SparkILoop$$process$1.apply$mcZ$sp(SparkILoop.scala:996)
at org.apache.spark.repl.SparkILoop$$anonfun$org$apache$spark$repl$SparkILoop$$process$1.apply(SparkILoop.scala:944)
at org.apache.spark.repl.SparkILoop$$anonfun$org$apache$spark$repl$SparkILoop$$process$1.apply(SparkILoop.scala:944)
at scala.tools.nsc.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:135)
at org.apache.spark.repl.SparkILoop.org$apache$spark$repl$SparkILoop$$process(SparkILoop.scala:944)
at org.apache.spark.repl.SparkILoop.process(SparkILoop.scala:1058)
at org.apache.spark.repl.Main$.main(Main.scala:31)
at org.apache.spark.repl.Main.main(Main.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.spark.deploy.SparkSubmit$.org$apache$spark$deploy$SparkSubmit$$runMain(SparkSubmit.scala:569)
at org.apache.spark.deploy.SparkSubmit$.doRunMain$1(SparkSubmit.scala:166)
at org.apache.spark.deploy.SparkSubmit$.submit(SparkSubmit.scala:189)
at org.apache.spark.deploy.SparkSubmit$.main(SparkSubmit.scala:110)
at org.apache.spark.deploy.SparkSubmit.main(SparkSubmit.scala)
Caused by: java.io.NotSerializableException: $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$rfmc$
Serialization stack:
- object not serializable (class: $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$rfmc$, value: $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$rfmc$#757fc606)
- field (class: $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$rfmc$$anonfun$17, name: $outer, type: class $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$rfmc$)
- object (class $iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$rfmc$$anonfun$17, <function1>)
at org.apache.spark.serializer.SerializationDebugger$.improveException(SerializationDebugger.scala:38)
at org.apache.spark.serializer.JavaSerializationStream.writeObject(JavaSerializer.scala:47)
at org.apache.spark.serializer.JavaSerializerInstance.serialize(JavaSerializer.scala:80)
at org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:164)
... 52 more
Update 2
The way I am defining my objects and functions is like this:
object rfmc {
def constructrfmc() = {
// Everything goes inside including the custom key and partitioner
// code defined above
}
}
Update 3
The way I am defining my code in eclipse which works perfectly is:
object rfmc extends App {
// Everything goes inside including the custom key and partitioner
// code defined above
}
I also created a JAR for this code and ran using spark-submit and that too worked perfectly.

Answer 1

To address the issue that RFMCKey is already defined, you need to swap the order of your case class and object declaration as explained in this issue.
Regarding your updates, there may be some limitations in the spark-shell that can't let execute any arbitrary code (such as with accumulators). To get more insight on the serialization mechanism, you should pass the following option -Dsun.io.serialization.extendedDebugInfo=true. Remember that the spark-shell is more of an exploratory utility to test small portions of code or new features iteratively thanks to the REPL, and not a fully-fledged production-ready utility that should be used extensively to test your code.
Your safest option here is to package your app into a jar and set up Spark in standalone mode, and run spark-submit with your packaged jar. As reflected in update 3 and 4 of your post, you'll need to update your code to wrap it into an object so that it is the entry point of your job. This will enable you to make sure your code is not at fault here.