[jira] Issue Comment Edited: (HBASE-1076) CME in HStore.notifyChangedReadersObservers

["Andrew Purtell (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-1076?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12716719#action_12716719 ] 

Andrew Purtell edited comment on HBASE-1076 at 6/5/09 11:52 AM:
----------------------------------------------------------------

Stack: This is not a CME. Its NPE. 

Sorry, next time, coffee first. 

It looks to me like 'readers' became null between the test

{code}
readers != null
{code}

and 

{code}
readers.length > 0
{code}

How reliable are line numbers in stack traces? Just below on line 334 is potentially suspicious {{this.previousNext.getRow()}}

      was (Author: apurtell):
    Stack: This is not a CME. Its NPE. 

Sorry, next time, coffee first. 

It looks to me like 'readers' became null between the test

{code}
readers != null
{code}

and 

{code}
readers.length > 0
{code}
  
> CME in HStore.notifyChangedReadersObservers
> -------------------------------------------
>
>                 Key: HBASE-1076
>                 URL: https://issues.apache.org/jira/browse/HBASE-1076
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.19.1
>            Reporter: Andrew Purtell
>            Assignee: stack
>            Priority: Blocker
>             Fix For: 0.19.4
>
>
> Running latest trunk plus jimk's patch for HBASE-543: 
> 2008-12-21 12:47:31,741 DEBUG org.apache.hadoop.hbase.regionserver.HStoreScanner
> : Added a StoreFileScanner to outstanding HStoreScanner
> 2008-12-21 12:47:31,741 FATAL org.apache.hadoop.hbase.regionserver.MemcacheFlusher: Replay of hlog required. Forcing server shutdown
> org.apache.hadoop.hbase.DroppedSnapshotException: region: urls,http|playvideogame.net|,1229725620550
>         at org.apache.hadoop.hbase.regionserver.HRegion.internalFlushcache(HRegion.java:880)
>         at org.apache.hadoop.hbase.regionserver.HRegion.flushcache(HRegion.java:773)
>         at org.apache.hadoop.hbase.regionserver.MemcacheFlusher.flushRegion(MemcacheFlusher.java:228)
>         at org.apache.hadoop.hbase.regionserver.MemcacheFlusher.flushSomeRegions(MemcacheFlusher.java:292)
>         at org.apache.hadoop.hbase.regionserver.MemcacheFlusher.reclaimMemcacheMemory(MemcacheFlusher.java:262)
>         at org.apache.hadoop.hbase.regionserver.HRegionServer.batchUpdates(HRegionServer.java:1594)
>         at sun.reflect.GeneratedMethodAccessor12.invoke(Unknown Source)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>         at java.lang.reflect.Method.invoke(Method.java:597)
>         at org.apache.hadoop.hbase.ipc.HBaseRPC$Server.call(HBaseRPC.java:632)
>         at org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:894)
> Caused by: java.util.ConcurrentModificationException
>         at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
>         at java.util.HashMap$KeyIterator.next(HashMap.java:828)
>         at org.apache.hadoop.hbase.regionserver.HStore.notifyChangedReadersObservers(HStore.java:736)
>         at org.apache.hadoop.hbase.regionserver.HStore.updateReaders(HStore.java:724)
>         at org.apache.hadoop.hbase.regionserver.HStore.internalFlushCache(HStore.java:693)
>         at org.apache.hadoop.hbase.regionserver.HStore.flushCache(HStore.java:629)
>         at org.apache.hadoop.hbase.regionserver.HRegion.internalFlushcache(HRegion.java:865)
>         ... 10 more

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