Hi,
I tried take(1500) and test.collect and these both work on the "single" map
statement.
I'm very new to Kryo serialisation, I managed to find some code and I copied
and pasted and that's what originally made the single map statement work:
class MyRegistrator extends KryoRegistrator {
override def registerClasses(kryo: Kryo) {
kryo.register(classOf[org.joda.time.DateTime])
}
}
Is it because the groupBy sees a different class type? Maybe Array[DateTime]? I
don’t want to find the answer by trial and error though.
Alex
-----Original Message-----
From: Sean Owen [mailto:so...@cloudera.com]
Sent: 14 January 2016 14:07
To: Spencer, Alex (Santander)
Cc: user@spark.apache.org
Subject: Re: NPE when using Joda DateTime
It does look somehow like the state of the DateTime object isn't being
recreated properly on deserialization somehow, given where the NPE occurs (look
at the Joda source code). However the object is java.io.Serializable. Are you
sure the Kryo serialization is correct?
It doesn't quite explain why the map operation works by itself. It could be the
difference between executing locally (take(1) will look at 1 partition in 1
task which prefers to be local) and executing remotely (groupBy is going to
need a shuffle).
On Thu, Jan 14, 2016 at 1:01 PM, Spencer, Alex (Santander)
<alex.spen...@santander.co.uk.invalid> wrote:
> Hello,
>
>
>
> I was wondering if somebody is able to help me get to the bottom of a
> null pointer exception I’m seeing in my code. I’ve managed to narrow
> down a problem in a larger class to my use of Joda’s DateTime
> functions. I’ve successfully run my code in scala, but I’ve hit a few
> problems when adapting it to run in spark.
>
>
>
> Spark version: 1.3.0
>
> Scala version: 2.10.4
>
> Java HotSpot 1.7
>
>
>
> I have a small case class called Transaction, which looks something
> like
> this:
>
>
>
> case class Transaction(date : org.joda.time.DateTime = new
> org.joda.time.DateTime())
>
>
>
> I have an RDD[Transactions] trans:
>
> org.apache.spark.rdd.RDD[Transaction] = MapPartitionsRDD[4] at map at
> <console>:44
>
>
>
> I am able to run this successfully:
>
>
>
> val test = trans.map(_.date.minusYears(10))
>
> test.take(1)
>
>
>
> However if I do:
>
>
>
> val groupedTrans = trans.groupBy(_.account)
>
>
>
> //For each group, process transactions in turn:
>
> val test = groupedTrans.flatMap { case (_, transList) =>
>
> transList.map {transaction =>
>
> transaction.date.minusYears(10)
>
> }
>
> }
>
> test.take(1)
>
>
>
> I get:
>
>
>
> java.lang.NullPointerException
>
> at org.joda.time.DateTime.minusYears(DateTime.java:1268)
>
>
>
> Should the second operation not be equivalent to the first .map one?
> (It’s a long way round of producing my error – but it’s extremely
> similar to what’s happening in my class).
>
>
>
> I’ve got a custom registration class for Kryo which I think is working
> - before I added this the original .map did not work – but shouldn’t
> it be able to serialize all instances of Joda DateTime?
>
>
>
> Thank you for any help / pointers you can give me.
>
>
>
> Kind Regards,
>
> Alex.
>
>
>
> Alex Spencer
>
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