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https://issues.apache.org/jira/browse/HDFS-10673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16290484#comment-16290484
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Jack Bearden commented on HDFS-10673:
-------------------------------------
Since the NullPointerException is being thrown from a rather benign function,
it seems safe to just guard against the null element at position 0. I could
very well be mistaken, however. The following code change appears to remedy the
edge case on my dev cluster:
{code}
// FSPermissionChecker#getINodeAttrs
if (i == 0 && pathByNameArr[i] == null) {
elements[i] = "";
} else {
elements[i] = DFSUtil.bytes2String(pathByNameArr[i]);
}
{code}
> Optimize FSPermissionChecker's internal path usage
> --------------------------------------------------
>
> Key: HDFS-10673
> URL: https://issues.apache.org/jira/browse/HDFS-10673
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Fix For: 2.8.0, 2.7.4, 3.0.0-alpha1
>
> Attachments: HDFS-10673-branch-2.7.00.patch, HDFS-10673.1.patch,
> HDFS-10673.2.patch, HDFS-10673.patch
>
>
> The INodeAttributeProvider and AccessControlEnforcer features degrade
> performance and generate excessive garbage even when neither is used. Main
> issues:
> # A byte[][] of components is unnecessarily created. Each path component
> lookup converts a subrange of the byte[][] to a new String[] - then not used
> by default attribute provider.
> # Subaccess checks are insanely expensive. The full path of every subdir is
> created by walking up the inode tree, creating a INode[], building a string
> by converting each inode's byte[] name to a string, etc. Which will only be
> used if there's an exception.
> The expensive of #1 should only be incurred when using the provider/enforcer
> feature. For #2, paths should be created on-demand for exceptions.
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