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https://issues.apache.org/jira/browse/HDFS-15792?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17273927#comment-17273927
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Renukaprasad C commented on HDFS-15792:
---------------------------------------
No new functiolity added, just replaced Hashmap with ConcurrentHashMap to avoid
the Hashmap usage issue. So, no new tests added. Existing tests cover the
functionality.
Same has been verified with test code under -
https://stackoverflow.com/questions/29967401/strange-hashmap-exception-hashmapnode-cannot-be-cast-to-hashmaptreenode/29971168,
I can reproduce the issue randomly with the given code. Same test has been
tested with ConcurrentHashmap and then not able to reproduce the
ClasscastException.
> ClasscastException while loading FSImage
> ----------------------------------------
>
> Key: HDFS-15792
> URL: https://issues.apache.org/jira/browse/HDFS-15792
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: nn
> Reporter: Renukaprasad C
> Assignee: Renukaprasad C
> Priority: Major
> Attachments: HDFS-15792.001.patch, HDFS-15792.002.patch,
> image-2021-01-27-12-00-34-846.png
>
>
> FSImage loading has failed with ClasscastException -
> java.lang.ClassCastException: java.util.HashMap$Node cannot be cast to
> java.util.HashMap$TreeNode.
> This is the usage issue with Hashmap in concurrent scenarios.
> Same issue has been reported on Java & closed as usage issue. -
> https://bugs.openjdk.java.net/browse/JDK-8173671
> 2020-12-28 11:36:26,127 | ERROR | main | An exception occurred when loading
> INODE from fsiamge. | FSImageFormatProtobuf.java:442
> java.lang.
> : java.util.HashMap$Node cannot be cast to java.util.HashMap$TreeNode
> at java.util.HashMap$TreeNode.moveRootToFront(HashMap.java:1835)
> at java.util.HashMap$TreeNode.treeify(HashMap.java:1951)
> at java.util.HashMap.treeifyBin(HashMap.java:772)
> at java.util.HashMap.putVal(HashMap.java:644)
> at java.util.HashMap.put(HashMap.java:612)
> at
> org.apache.hadoop.hdfs.util.ReferenceCountMap.put(ReferenceCountMap.java:53)
> at
> org.apache.hadoop.hdfs.server.namenode.AclStorage.addAclFeature(AclStorage.java:391)
> at
> org.apache.hadoop.hdfs.server.namenode.INodeWithAdditionalFields.addAclFeature(INodeWithAdditionalFields.java:349)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode$Loader.loadINodeDirectory(FSImageFormatPBINode.java:225)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode$Loader.loadINode(FSImageFormatPBINode.java:406)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode$Loader.readPBINodes(FSImageFormatPBINode.java:367)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode$Loader.loadINodeSection(FSImageFormatPBINode.java:342)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf$Loader$2.call(FSImageFormatProtobuf.java:469)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:748)
> 2020-12-28 11:36:26,130 | ERROR | main | Failed to load image from
> FSImageFile(file=/srv/BigData/namenode/current/fsimage_0000000000198227480,
> cpktTxId=0000000000198227480) | FSImage.java:738
> java.io.IOException: java.lang.ClassCastException: java.util.HashMap$Node
> cannot be cast to java.util.HashMap$TreeNode
> at
> org.apache.hadoop.io.MultipleIOException$Builder.add(MultipleIOException.java:68)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf$Loader.runLoaderTasks(FSImageFormatProtobuf.java:444)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf$Loader.loadInternal(FSImageFormatProtobuf.java:360)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf$Loader.load(FSImageFormatProtobuf.java:263)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormat$LoaderDelegator.load(FSImageFormat.java:227)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:971)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:955)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImageFile(FSImage.java:820)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImage.loadFSImage(FSImage.java:733)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImage.recoverTransitionRead(FSImage.java:331)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFSImage(FSNamesystem.java:1113)
> at
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem.loadFromDisk(FSNamesystem.java:730)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.loadNamesystem(NameNode.java:648)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.initialize(NameNode.java:710)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:953)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.<init>(NameNode.java:926)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.createNameNode(NameNode.java:1665)
> at
> org.apache.hadoop.hdfs.server.namenode.NameNode.main(NameNode.java:1735)
> Caused by: java.lang.ClassCastException: java.util.HashMap$Node cannot be
> cast to java.util.HashMap$TreeNode
> at java.util.HashMap$TreeNode.moveRootToFront(HashMap.java:1835)
> at java.util.HashMap$TreeNode.treeify(HashMap.java:1951)
> at java.util.HashMap.treeifyBin(HashMap.java:772)
> at java.util.HashMap.putVal(HashMap.java:644)
> at java.util.HashMap.put(HashMap.java:612)
> at
> org.apache.hadoop.hdfs.util.ReferenceCountMap.put(ReferenceCountMap.java:53)
> at
> org.apache.hadoop.hdfs.server.namenode.AclStorage.addAclFeature(AclStorage.java:391)
> at
> org.apache.hadoop.hdfs.server.namenode.INodeWithAdditionalFields.addAclFeature(INodeWithAdditionalFields.java:349)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode$Loader.loadINodeDirectory(FSImageFormatPBINode.java:225)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode$Loader.loadINode(FSImageFormatPBINode.java:406)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode$Loader.readPBINodes(FSImageFormatPBINode.java:367)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatPBINode$Loader.loadINodeSection(FSImageFormatPBINode.java:342)
> at
> org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf$Loader$2.call(FSImageFormatProtobuf.java:469)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
> at java.lang.Thread.run(Thread.java:748)
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