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https://issues.apache.org/jira/browse/HDFS-8453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14560258#comment-14560258
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Walter Su commented on HDFS-8453:
---------------------------------
I didn't see any difference between {{refreshLocatedBlock}} and old version's
{{getBlockAt}}
This is old version
{code}
protected LocatedBlock getBlockAt(long blkStartOffset)
{code}
This is new version
{code}
protected LocatedBlock refreshLocatedBlock(LocatedBlock block) {
LocatedBlock lb = getBlockGroupAt(block.getStartOffset());
{code}
You didn't pass blkStartOffset, you get blkStartOffset from inside. So there is
no difference.
This line really matters. It resolves the issue.
{code}
+ bg.getStartOffset(), bg.isCorrupt(), null);
{code}
The solution is to make it meaningless.
> Erasure coding: properly assign start offset for internal blocks in a block
> group
> ---------------------------------------------------------------------------------
>
> Key: HDFS-8453
> URL: https://issues.apache.org/jira/browse/HDFS-8453
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Zhe Zhang
> Assignee: Zhe Zhang
> Attachments: HDFS-8453-HDFS-7285.00.patch
>
>
> {code}
> void actualGetFromOneDataNode(final DNAddrPair datanode,
> ...
> LocatedBlock block = getBlockAt(blockStartOffset);
> ...
> fetchBlockAt(block.getStartOffset());
> {code}
> The {{blockStartOffset}} here is from inner block. For parity blocks, the
> offset will overlap with the next block group, and we may end up with
> fetching wrong block. So we have to assign a meaningful start offset for
> internal blocks in a block group, especially for parity blocks.
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