[
https://issues.apache.org/jira/browse/HDFS-6428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14005135#comment-14005135
]
Yongjun Zhang commented on HDFS-6428:
-------------------------------------
BTW, the synchronized blocks described in the comment below existed before
HDFS-5705, or before HM was replaced with CHM. These synchronized blocks are
for updating data and collecting data from the map (not add, remove entry), so
there is the need to have them to block other threads from changing the data.
{quote}
So to sum up: if we don't want to get CMEs, we need to add synchronized
(dataset) blocks around the stuff that is accessing bpSlices. It looks like
this has been done in a few places, but not in others, and there is a TODO in
the code to fix this.
{quote}
Thanks.
> TestWebHdfsWithMultipleNameNodes failed with ConcurrentModificationException
> ----------------------------------------------------------------------------
>
> Key: HDFS-6428
> URL: https://issues.apache.org/jira/browse/HDFS-6428
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: webhdfs
> Reporter: Yongjun Zhang
> Assignee: Yongjun Zhang
> Attachments: HDFS-6428.001.patch
>
>
> TestWebHdfsWithMultipleNameNodes failed as follows:
> {code}
> Running org.apache.hadoop.hdfs.web.TestWebHdfsWithMultipleNameNodes
> Tests run: 2, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 8.643 sec <<<
> FAILURE! - in org.apache.hadoop.hdfs.web.TestWebHdfsWithMultipleNameNodes
> org.apache.hadoop.hdfs.web.TestWebHdfsWithMultipleNameNodes Time elapsed:
> 3.771 sec <<< ERROR!
> java.util.ConcurrentModificationException: null
> at java.util.HashMap$HashIterator.nextEntry(HashMap.java:894)
> at java.util.HashMap$EntryIterator.next(HashMap.java:934)
> at java.util.HashMap$EntryIterator.next(HashMap.java:932)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeImpl.shutdown(FsVolumeImpl.java:251)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsVolumeList.shutdown(FsVolumeList.java:249)
> at
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl.shutdown(FsDatasetImpl.java:1389)
> at
> org.apache.hadoop.hdfs.server.datanode.DataNode.shutdown(DataNode.java:1304)
> at
> org.apache.hadoop.hdfs.MiniDFSCluster.shutdownDataNodes(MiniDFSCluster.java:1555)
> at
> org.apache.hadoop.hdfs.MiniDFSCluster.shutdown(MiniDFSCluster.java:1530)
> at
> org.apache.hadoop.hdfs.MiniDFSCluster.shutdown(MiniDFSCluster.java:1514)
> at
> org.apache.hadoop.hdfs.web.TestWebHdfsWithMultipleNameNodes.shutdownCluster(TestWebHdfsWithMultipleNameNodes.java:99)
> {code}
--
This message was sent by Atlassian JIRA
(v6.2#6252)
