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https://issues.apache.org/jira/browse/HDFS-7211?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14163827#comment-14163827
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Zhe Zhang commented on HDFS-7211:
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[~tlipcon] We just encountered an issue where a DN is being decommissioned with
a large number of blocks (10,000s). Those block invalidation requests are
inserted into the unordered {{node2blocks}}. Therefore some blocks are "flushed
around" in the set and are not invalidated for a long time. Are you aware of an
ordered (and lightweight) collection type that we can use?
> Block invalidation work should be ordered
> -----------------------------------------
>
> Key: HDFS-7211
> URL: https://issues.apache.org/jira/browse/HDFS-7211
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Zhe Zhang
> Assignee: Zhe Zhang
>
> {{InvalidateBlocks#node2blocks}} uses an unordered {{LightWeightHashSet}} to
> store blocks (to be invalidated) on the same DN. This causes poor ordering
> when a single DN has a large number of blocks to invalidate. Blocks should be
> invalidated following the order of invalidation commands -- at least roughly.
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