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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-12832) INode.getFullPathName may throw ArrayIndexOutOfBoundsException lead to NameNode exit
Date Wed, 22 Nov 2017 20:18:01 GMT

     [ https://issues.apache.org/jira/browse/HDFS-12832?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Konstantin Shvachko updated HDFS-12832:
---------------------------------------
    Attachment: HDFS-12832.002.patch

The 002 patch fixes the issue of calling {{getFullPathName()}} without holding the lock. The
fix is to compute {{getFullPathName()}} inside  {{BlockReconstructionWork}} constructor, which
is called under the lock. Just as explained earlier.
I did not write a unit as we would have to perform a major surgery on FSNamesystem in order
to get exacvtly that {{ArrayIndexOutOfBoundsException}}.
Instead I loo0ked through all calls of {{getFullPathName()}}, making sure it is done under
a lock. Found one place where it is not - in Fsck. Will file a jira for that shortly.

> INode.getFullPathName may throw ArrayIndexOutOfBoundsException lead to NameNode exit
> ------------------------------------------------------------------------------------
>
>                 Key: HDFS-12832
>                 URL: https://issues.apache.org/jira/browse/HDFS-12832
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.7.4, 3.0.0-beta1
>            Reporter: DENG FEI
>            Priority: Critical
>              Labels: release-blocker
>         Attachments: HDFS-12832-trunk-001.patch, HDFS-12832.002.patch, exception.log
>
>
> {code:title=INode.java|borderStyle=solid}
> public String getFullPathName() {
>     // Get the full path name of this inode.
>     if (isRoot()) {
>       return Path.SEPARATOR;
>     }
>     // compute size of needed bytes for the path
>     int idx = 0;
>     for (INode inode = this; inode != null; inode = inode.getParent()) {
>       // add component + delimiter (if not tail component)
>       idx += inode.getLocalNameBytes().length + (inode != this ? 1 : 0);
>     }
>     byte[] path = new byte[idx];
>     for (INode inode = this; inode != null; inode = inode.getParent()) {
>       if (inode != this) {
>         path[--idx] = Path.SEPARATOR_CHAR;
>       }
>       byte[] name = inode.getLocalNameBytes();
>       idx -= name.length;
>       System.arraycopy(name, 0, path, idx, name.length);
>     }
>     return DFSUtil.bytes2String(path);
>   }
> {code}
> We found ArrayIndexOutOfBoundsException at _{color:#707070}System.arraycopy(name, 0,
path, idx, name.length){color}_ when ReplicaMonitor work ,and the NameNode will quit.
> It seems the two loop is not synchronized, the path's length is changed.



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