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Date: Fri, 5 Jun 2009 11:31:07 -0700 (PDT)
From: "stack (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Commented: (HBASE-1076) CME in
 HStore.notifyChangedReadersObservers
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    [ https://issues.apache.org/jira/browse/HBASE-1076?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12716710#action_12716710 ] 

stack commented on HBASE-1076:
------------------------------

This is not a CME.  Its NPE.

Here is code:

{code}
328       MapFile.Reader [] readers = this.store.getReaders();
329       if (this.scanners[HSFS_INDEX] == null && readers != null &&
330           readers.length > 0) {
{code}

Its not the this.store because that is never cleared.

Its not the readers because stack variable and we just checked it not null.

This this.scanners is never cleared.

Can you see what it is?


> 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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