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https://issues.apache.org/jira/browse/HDFS-13947?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16635677#comment-16635677
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BELUGA BEHR commented on HDFS-13947:
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[~knanasi] Thanks for the feedback!
# I added spaces. Thanks for pointing that out
# The code in {{getDiskReport}} is an artifact from the original code. There
are two lists: a list of volumes and a list of scanners for each volume. If
you wanted to know which scanner belonged to which volume, they were both
located at the same index in their respective lists. However, when skipping a
'provided' volume, we had to put a place holder in the lost of scanners or else
the list of scanners would be shorter than the list of volumes and the mapping
would be off. I've removed this setup and added another data structure to
support mapping volumes to block pools explicitly.
# I think we should still move forward with the change in the default value.
Even with the default value changing, nothing changes functionally. If a user
have their value explicitly set as '1000', it will still work exactly the
same. The only difference now is that a customer with a specified value of
1000 will be logged as -1.
> Review of DirectoryScanner Class
> --------------------------------
>
> Key: HDFS-13947
> URL: https://issues.apache.org/jira/browse/HDFS-13947
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 3.2.0
> Reporter: BELUGA BEHR
> Assignee: BELUGA BEHR
> Priority: Major
> Attachments: HDFS-13947.1.patch, HDFS-13947.2.patch,
> HDFS-13947.3.patch, HDFS-13947.4.patch
>
>
> Review of Directory Scanner. Replaced a lot of code with Guava MultiMap.
> Some general house cleaning and improved logging. For performance, using
> {{ArrayList}} instead of {{LinkedList}} where possible, especially since
> these lists can be quite large a LinkedList will consume a lot of memory and
> be slow to sort/iterate over.
> https://stackoverflow.com/questions/322715/when-to-use-linkedlist-over-arraylist-in-java
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