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https://issues.apache.org/jira/browse/HDFS-11179?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15700826#comment-15700826
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Takanobu Asanuma commented on HDFS-11179:
-----------------------------------------
When a blockId is a large number, this method doesn't remove the block
correctly.
{code:title=LightWeightHashSet.java}
protected LinkedElement<T> removeElem(final T key) {
LinkedElement<T> found = null;
final int hashCode = key.hashCode();
final int index = getIndex(hashCode);
if (entries[index] == null) {
return null;
{code}
> LightWeightHashSet can't remove blocks correctly which have a large number
> blockId
> ----------------------------------------------------------------------------------
>
> Key: HDFS-11179
> URL: https://issues.apache.org/jira/browse/HDFS-11179
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.0.0-alpha1
> Reporter: Takanobu Asanuma
> Assignee: Takanobu Asanuma
> Priority: Blocker
>
> Our test cluster has faced a problem that
> {{postponedMisreplicatedBlocksCount}} has been going below zero. The version
> of the cluster is a recent 3.0. We haven't created any EC files yet. This is
> the NN's log:
> {noformat}
> Rescan of postponedMisreplicatedBlocks completed in 13 msecs. 448 blocks are
> left. 176 blocks are removed.
> Rescan of postponedMisreplicatedBlocks completed in 13 msecs. 272 blocks are
> left. 176 blocks are removed.
> Rescan of postponedMisreplicatedBlocks completed in 14 msecs. 96 blocks are
> left. 176 blocks are removed.
> Rescan of postponedMisreplicatedBlocks completed in 327 msecs. -77 blocks are
> left. 177 blocks are removed.
> Rescan of postponedMisreplicatedBlocks completed in 15 msecs. -253 blocks are
> left. 179 blocks are removed.
> Rescan of postponedMisreplicatedBlocks completed in 14 msecs. -432 blocks are
> left. 179 blocks are removed.
> {noformat}
> I looked into this issue and found that it is caused by
> {{LightWeightHashSet}} which is used for {{postponedMisreplicatedBlocks}}
> recently. When {{LightWeightHashSet}} remove blocks which have a large number
> blockId, overflows happen and the blocks can't be removed correctly(, let
> alone ec blocks whose blockId starts with the minimum of long).
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