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https://issues.apache.org/jira/browse/HDFS-3616?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jing Zhao updated HDFS-3616:
----------------------------
Attachment: HDFS-3616.trunk.001.patch
After checking the code, I guess the exception is caused by this process:
1. In DataNode#shutdown(), DataNode#shouldRun is set to false.
2. BPServiceActor#run() stops running, and runs BPServiceActor#cleanUp().
3. While executing BPServiceActor#cleanUp(), DataNode#shutdownBlockPool() is
called, where blockPoolManager.remove(bpos) is executed before
"this.blockPoolManager.shutDownAll();" is called in DataNode#shutdown(). Thus
the corresponding BPOfferService cannot be seen and shutdown by
blockPoolManager#shutDownAll() since it has been removed from
BlockPoolManager#offerServices.
4. The actor thread continues running DataNode#shutdownBlockPool() which will
finally tries to remove record from FsVolumeImpl#bpSlices, while the DataNode
shutdown thread runs into FsVolumeImpl#shutdown() which iterates the bpSlices.
Thus the ConcurrentModificationException may be thrown.
So to avoid changing other code, maybe we can simply change bpSlices from
HashMap to ConcurrentHashMap? A simple patch based on this is attached.
> TestWebHdfsWithMultipleNameNodes fails with ConcurrentModificationException
> in DN shutdown
> ------------------------------------------------------------------------------------------
>
> Key: HDFS-3616
> URL: https://issues.apache.org/jira/browse/HDFS-3616
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: data-node
> Affects Versions: 2.0.0-alpha, 3.0.0
> Reporter: Uma Maheswara Rao G
> Assignee: Jing Zhao
> Attachments: HDFS-3616.trunk.001.patch
>
>
> I have seen this in precommit build #2743
> {noformat}
> java.util.ConcurrentModificationException
> at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
> at java.util.HashMap$EntryIterator.next(HashMap.java:834)
> at java.util.HashMap$EntryIterator.next(HashMap.java:832)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeImpl.shutdown(FsVolumeImpl.java:209)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeList.shutdown(FsVolumeList.java:168)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.shutdown(FsDatasetImpl.java:1214)
> at
> org.apache.hadoop.hdfs.server.datanode.DataNode.shutdown(DataNode.java:1105)
> at
> org.apache.hadoop.hdfs.MiniDFSCluster.shutdownDataNodes(MiniDFSCluster.java:1324)
> at
> org.apache.hadoop.hdfs.MiniDFSCluster.shutdown(MiniDFSCluster.java:1304)
> at
> org.apache.hadoop.hdfs.web.TestWebHdfsWithMultipleNameNodes.shutdownCluster(TestWebHdfsWithMultipleNameNodes.java:100)
> {noformat}
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