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https://issues.apache.org/jira/browse/HDFS-7686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14317511#comment-14317511
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Colin Patrick McCabe commented on HDFS-7686:
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bq. Unused Iterator import in the test, LoadingCache import in VolumeScanner
ok
bq. I like the cache since it's a nice way of preventing scanning the same
blocks over and over again, but it'd be good to also use a LinkedHashMap
instead of the LinkedList and also check existence in there before adding. That
way we never have dupes in the suspect queue. It seems possible to have a
working set bigger than the 1000 element cache size, like if an entire disk
goes bad.
good idea... I'll use a {{LinkedHashSet}}.
> Re-add rapid rescan of possibly corrupt block feature to the block scanner
> --------------------------------------------------------------------------
>
> Key: HDFS-7686
> URL: https://issues.apache.org/jira/browse/HDFS-7686
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 3.0.0
> Reporter: Rushabh S Shah
> Assignee: Colin Patrick McCabe
> Priority: Blocker
> Attachments: HDFS-7686.002.patch
>
>
> When doing a transferTo (aka sendfile operation) from the DataNode to a
> client, we may hit an I/O error from the disk. If we believe this is the
> case, we should be able to tell the block scanner to rescan that block soon.
> The feature was originally implemented in HDFS-7548 but was removed by
> HDFS-7430. We should re-add it.
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