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Date: Thu, 12 Aug 2010 13:20:16 -0400 (EDT)
From: "stack (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Subject: [jira] Commented: (HBASE-2909) SoftValueSortedMap is broken, can
 generate NPEs
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    [ https://issues.apache.org/jira/browse/HBASE-2909?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12897846#action_12897846 ] 

stack commented on HBASE-2909:
------------------------------

+1

> SoftValueSortedMap is broken, can generate NPEs
> -----------------------------------------------
>
>                 Key: HBASE-2909
>                 URL: https://issues.apache.org/jira/browse/HBASE-2909
>             Project: HBase
>          Issue Type: Bug
>          Components: client
>    Affects Versions: 0.20.6, 0.89.20100621
>            Reporter: Jean-Daniel Cryans
>            Priority: Blocker
>             Fix For: 0.20.7, 0.90.0
>
>         Attachments: hbase-2909.patch
>
>
> The way SoftValueSortedMap is using SoftValues, it looks like that it's able to get it's keys garbage collected along with the values themselves. We got this issue in production but I was also able to randomly generate it using YCSB with 300 threads. Here's an example on 0.20 with jdk 1.6u14:
> {noformat}
> java.lang.NullPointerException
>         at org.apache.hadoop.hbase.util.Bytes.compareTo(Bytes.java:1036)
>         at org.apache.hadoop.hbase.util.Bytes$ByteArrayComparator.compare(Bytes.java:104)
>         at org.apache.hadoop.hbase.util.Bytes$ByteArrayComparator.compare(Bytes.java:96)
>         at java.util.TreeMap.cmp(TreeMap.java:1911)
>         at java.util.TreeMap.get(TreeMap.java:1835)
>         at org.apache.hadoop.hbase.util.SoftValueSortedMap.get(SoftValueSortedMap.java:91)
>         at org.apache.hadoop.hbase.client.HConnectionManager$TableServers.getCachedLocation(HConnectionManager.java:788)
>         at org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegionInMeta(HConnectionManager.java:651)
>         at org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegion(HConnectionManager.java:634)
>         at org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegion(HConnectionManager.java:601)
>         at org.apache.hadoop.hbase.client.HTable.<init>(HTable.java:128)
>         at org.apache.hadoop.hbase.thrift.ThriftServer$HBaseHandler.getTable(ThriftServer.java:262)
>         at org.apache.hadoop.hbase.thrift.ThriftServer$HBaseHandler.mutateRowTs(ThriftServer.java:585)
>         at org.apache.hadoop.hbase.thrift.ThriftServer$HBaseHandler.mutateRow(ThriftServer.java:578)
>         at org.apache.hadoop.hbase.thrift.generated.Hbase$Processor$mutateRow.process(Hbase.java:2345)
>         at org.apache.hadoop.hbase.thrift.generated.Hbase$Processor.process(Hbase.java:1988)
>         at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:259)
>         at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
>         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
>         at java.lang.Thread.run(Thread.java:619)
> {noformat}
> In this specific case, the null cannot be the passed key because it's coming from HTable which uses HConstants.EMPTY_START_ROW. It cannot be a null key that was inserted previously because we would have got the NPE at insert time. This can only mean that some key *became* null.

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