[jira] [Commented] (SAMZA-80) KV cache store fails with NPE

[Chris Riccomini (JIRA)]

    [ 
https://issues.apache.org/jira/browse/SAMZA-80?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13837981#comment-13837981
 ] 

Chris Riccomini commented on SAMZA-80:
--------------------------------------

I kind of couldn't believe that Scala 2.8's double linked list is so broken. As 
a sanity check, I ran this 2.8.1 code:

{code}
    val tail = new scala.collection.mutable.DoubleLinkedList[Int]()
    val zero = new scala.collection.mutable.DoubleLinkedList[Int](0, tail)
    val one = new scala.collection.mutable.DoubleLinkedList[Int](1, zero)
    val two = new scala.collection.mutable.DoubleLinkedList[Int](2, one)
    
    System.err.println(two)
    System.err.println(one.prev)
{code}

And got:

{noformat}
DoubleLinkedList(2, 1, 0)
null
{noformat}

The same code on 2.9.2 prints:

{noformat}
DoubleLinkedList(2, 1, 0)
DoubleLinkedList(2, 1, 0)
{noformat}

Scala 2.8 is definitely busted.

> KV cache store fails with NPE
> -----------------------------
>
>                 Key: SAMZA-80
>                 URL: https://issues.apache.org/jira/browse/SAMZA-80
>             Project: Samza
>          Issue Type: Bug
>          Components: kv
>    Affects Versions: 0.6.0
>            Reporter: Chris Riccomini
>            Assignee: Chris Riccomini
>             Fix For: 0.7.0
>
>         Attachments: SAMZA-80.0.patch
>
>
> I came across a situation in which a StreamTask with a store will trigger an 
> NPE in the caching class.
> {noformat}
> java.lang.NullPointerException
>   at 
> org.apache.samza.storage.kv.CachedStore$$anonfun$flush$2.apply(CachedStore.scala:144)
>   at 
> org.apache.samza.storage.kv.CachedStore$$anonfun$flush$2.apply(CachedStore.scala:142)
>   at 
> scala.collection.mutable.LinkedListLike$class.foreach(LinkedListLike.scala:111)
>   at 
> scala.collection.mutable.DoubleLinkedList.foreach(DoubleLinkedList.scala:41)
>   at org.apache.samza.storage.kv.CachedStore.flush(CachedStore.scala:142)
>   at 
> org.apache.samza.storage.kv.CachedStore$$anon$1.removeEldestEntry(CachedStore.scala:65)
>   at java.util.LinkedHashMap.addEntry(LinkedHashMap.java:410)
>   at java.util.HashMap.put(HashMap.java:385)
>   at org.apache.samza.storage.kv.CachedStore.get(CachedStore.scala:83)
>   at 
> org.apache.samza.storage.kv.KeyValueStorageEngine.get(KeyValueStorageEngine.scala:48)
>   at com.linkedin.samza.example.StatefulTask.process(StatefulTask.java:51)
>   at org.apache.samza.container.TaskInstance.process(TaskInstance.scala:168)
>   at 
> org.apache.samza.container.SamzaContainer.process(SamzaContainer.scala:563)
>   at org.apache.samza.container.SamzaContainer.run(SamzaContainer.scala:455)
>   at org.apache.samza.job.local.ThreadJob$$anon$1.run(ThreadJob.scala:42)
> {noformat}



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