[
https://issues.apache.org/jira/browse/SAMZA-80?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13830549#comment-13830549
]
Chris Riccomini commented on SAMZA-80:
--------------------------------------
Ok, I don't have a patch for this yet, but this bug is painful. In
CachedStore.scala, it appears that this cod is broken:
{noformat}
if (found.dirty.prev == null) {
this.dirty = found.dirty.next
this.dirty.prev = null
} else {
found.dirty.remove
}
{noformat}
In particular, the found.dirty.remove block never gets called. In particular, I
set a break point when the NPE is thrown, and I took a look at this.dirty.
Here's what I see:
{noformat}
this CachedStore$$anonfun$flush$2 (id=59)
$outer CachedStore<K,V> (id=69)
bitmap$0 1
cacheSize 1000
grizzled$slf4j$Logging$$_logger Logger (id=104)
metrics CachedStoreMetrics (id=106)
org$apache$samza$storage$kv$CachedStore$$cache
CachedStore$$anon$1 (id=70)
org$apache$samza$storage$kv$CachedStore$$dirty
DoubleLinkedList<A> (id=109)
elem "remote-nav-foot" (id=369)
next DoubleLinkedList<A> (id=370)
elem
"pulse-editor-update-article-submit-internal" (id=372)
next DoubleLinkedList<A> (id=373)
elem "pulse-editor-internal"
(id=375)
next DoubleLinkedList<A> (id=376)
elem
"pulse-editor-article-promotions-page-internal" (id=378)
next DoubleLinkedList<A>
(id=379)
elem
"profile_v2_treasury_landing" (id=381)
next
DoubleLinkedList<A> (id=382)
elem
"profile_v2_megaphone_discovery" (id=384)
next
DoubleLinkedList<A> (id=385)
elem
"profile_v2_activity_broadcasts_submit" (id=61)
next
DoubleLinkedList<A> (id=387)
elem "profile_v2_activity" (id=389)
next DoubleLinkedList<A> (id=390)
elem "nprofile-edit" (id=392)
next DoubleLinkedList<A> (id=393)
elem "remote-nav-foot" (id=395)
next DoubleLinkedList<A> (id=396)
elem "quickhelp-search-catalog" (id=398)
next DoubleLinkedList<A> (id=399)
prev null
prev null
prev null
prev null
prev
null
prev null
prev null
prev null
prev null
prev null
prev null
org$apache$samza$storage$kv$CachedStore$$dirtyCount 5
store SerializedKeyValueStore<K,V> (id=111)
writeBatchSize 500
batch$1 ArrayList<E> (id=90)
{noformat}
Of particular note here is that EVERY prev variable is null (!!).
I added a debug statement next to found.dirty.remove(), and indeed this method
is NEVER triggered. This results in totally broken dirty lists, since we treat
every removed node as though it's head, even if it's not. This leads to, among
other things, vastly different values between dirtyCount, and the number of
elements in this.dirty.
I'm going to try and replicate this from a test.
> 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
>
>
> 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}
--
This message was sent by Atlassian JIRA
(v6.1#6144)
